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Van der Waals quantum wells, naturally formed in two-dimensional layered materials with nanoscale thickness, possess many inherent advantages over conventional molecular beam epitaxy grown counterparts, and could bring up intriguing physics and applications. However, optical transitions originated from the series of quantized states in these emerging quantum wells are still elusive. Here, we show that multilayer black phosphorus appears to be an excellent candidate for van der Waals quantum wells with well-defined subbands and high optical quality. Using infrared absorption spectroscopy, we probe subband structures of multilayer black phosphorus with tens of atomic layers, revealing clear signatures for optical transitions with subband index as high as 10, far from what was attainable previously. Surprisingly, in addition to allowed transitions, an unexpected series of "forbidden" transitions is also evidently observed, which enables us to determine energy spacings separately for conduction and valence subbands. Furthermore, the linear tunability of subband spacings by temperature and strain is demonstrated. Our results are expected to facilitate potential applications for infrared optoelectronics based on tunable van der Waals quantum wells.

Understanding hydrogen-metal interactions is important in various fields of surface science, including the aqueous corrosion of metals. The interaction between atomic H and a Mg surface is a key process for the formation of sub-surface Mg hydride, which may play an important role in Mg aqueous corrosion. In the present work, we performed first-principles Density Functional Theory (DFT) calculations to study the mechanisms for hydrogen adsorption and crystalline Mg hydride formation under aqueous conditions. The Electron Localisation Function (ELF) is found to be a promising indicator for predicting stable H adsorption in the Mg surface. It is found that H adsorption and hydride layer formation is dominated by high ELF adsorption sites. Our calculations suggest that the on-surface adsorption of atomic H, OH radicals and atomic O could enhance the electron localisation at specific sites in the sub-surface region, thus forming effective H traps locally. This is predicted to result in the formation of a thermodynamically stable sub-surface hydride layer, which is a potential precursor of the crucial hydride corrosion product of magnesium.

A new framework for the parametric reconstruction of curved fibres from glass fibre-reinforced composite X-ray computed tomography data is proposed. It allows us to detect fibres in a fibre-reinforced polymer sample from a low-dose, low resolution computed tomography scan. An efficient curve representation is then used for each detected fibre, of which the parameters are estimated directly from few 2D high-resolution projection images. The framework is validated on both simulated and real data of glass fibre-reinforced polymers. The generated results demonstrate that it is robust to noise and requires less than 10 high-resolution projections to obtain reasonable fibre estimates. The method can also improve upon existing estimation frameworks relying on full 3D scans.

This conceptual design report provides a detailed account of the European Spallation Source neutrino Super Beam (ESS$\nu$SB) feasibility study. This facility has been proposed after the measurements reported in 2012 of a relatively large value of the neutrino mixing angle $\theta_{13}$, which raised the possibility of observing potential CP violation in the leptonic sector with conventional neutrino beams. The measured value of $\theta_{13}$ also privileges the $2^{nd}$ oscillation maximum for the discovery of CP violation instead of the more typically studied $1^{st}$ maximum. The sensitivity at this $2^{nd}$ oscillation maximum is about three times higher than at the $1^{st}$ one, which implies a reduced influence of systematic errors. Working at the $2^{nd}$ oscillation maximum requires a very intense neutrino beam with an appropriate energy. The world's most intense pulsed spallation neutron source, the European Spallation Source (ESS), will have a proton linac operating at 5\,MW power, 2\,GeV kinetic energy and 14~Hz repetition rate (3~ms pulse duration, 4\% duty cycle) for neutron production. In this design study it is proposed to double the repetition rate and compress the beam pulses to the level of microseconds in order to provide an additional 5~MW proton beam for neutrino production. The physics performance has been evaluated for such a neutrino super beam, in conjunction with a megaton-scale underground water Cherenkov neutrino detector installed at a distance of 360--550\,km from ESS. The ESS proton linac upgrades, the accumulator ring required for proton-pulse compression, the target station design and optimisation, the near and far detector complexes, and the physics potential of the facility are all described in this report. The ESS linac will be operational by 2025, at which point the implementation of upgrades for the neutrino facility could begin., Comment: 216 pages

Circularly polarized luminescent (CPL) films with high dissymmetry factors hold great potential for optoelectronic applications. Herei n , we propose a strategy for achieving strongly dissymetric CPL in nanocomposite films based on chira l i t y induction and energy transfer to semiconductor nanocrystals. First, focusing on a purely organic system, aggregation-induced emission (AIE) and CPL activity of organic liquid crystals (LCs) forming helical nanofilaments was detected, featuring green emission with high dissymmetry factors g(lum) similar to 10(-2). The handedness of helical filaments, and thus the sign of CPL, was controlled via minute amounts of a small chiral organic dopant. Second, nanocomposite films were fabricated by incorporating InP/ZnS semi-conductor quantum dots (QDs) into the LC matri x , which induced the chiral assembly of QDs and endowed them with chiroptical properties. Due to the spectral matching of the components, energy transfer (ET) from LC to QDs was possible enabling a convenient way of tuning CPL wavelengths by varying the LC/QD ratio. As obtained, composite films exhibited absolute glum values up to similar to 10(-2) and thermally on/off switchable luminescence. Overall, we demonstrate the induction of chiroptical properties by the assembly of nonchiral building QDs on the chiral organic template and energy transfer from organic films to QDs, representing a simple and versatile approach to tune the CPL activity of organic materials.

© 2022 Polish Academy of Sciences. All rights reserved.Rapid synthesis of delafossite CuAlO2 was achieved by a solid-state reaction method. The synthesized sample was subjected to phase analysis by X-ray diffraction. The desired crystalline phase was obtained and all peaks in the X-ray diffraction phase investigation were found to belong to the CuAlO2 pattern. Morphological and stoichiometric properties were defined by a scanning electron microscope and insitu attachment of energy dispersive spectroscopy. X-ray photoelectron spectroscopy measurements were done to provide a detailed elemental composition analysis in the parts per thousand ranges. X-ray photoelectron spectroscopy measurements revealed that the core level of the 4 electron species Cu 2p, Al 2p, and O 1s exists. The structural defects of CuAlO2 were investigated using the Agilent Cary Eclipse Fluorescence Spectrophotometer. The photoluminescence measurements showed that the near-band emission, cooper vacancy, and oxygen vacancy emission occurred. The nature of optical and magnetic properties of the CuAlO2 sample was defined by Quantum Design Physical Properties Measurement System and correlated with the X-ray photoelectron spectroscopy and photoluminescence results.

The use of bio-based building blocks for the synthesis of polymers is increasing day by day. Among the bio-based building blocks, eugenol is a highly promising monomer for the preparation of thermoset materials. In this study, we combined thiol-ene photopolymerization (TEP) and thermal azide-alkyne cycloaddition click reactions to prepare eugenol-based thermally stable, P-, N-, and Si-containing networks. To this end, we synthesized a P-containing, eugenol-based monomer bearing azide group and a siloxane compound containing an alkyne group. By mixing these monomers with multifunctional thiols and by utilizing a dual-curing strategy, we managed to obtain optically transparent and thermally stable coatings with excellent adhesion to glass substrates. Thermal stability, optical transmittance, pendulum hardness, solvent resistance, and the adhesion performance of the coatings were evaluated. The gel contents of the thermoset materials were found to be over 95%. At 600 °C, the char yields of the dual-cured coatings were found to be over 30%. Coatings were also found to be resistant to acidic and basic conditions as well as solvents.

The coaxial stacking of two single-wall carbon nanotubes (SWCNTs) into a double-wall carbon nanotube (DWCNT), forming a so-called one-dimensional van der Waals structure, leads to synergetic effects that dramatically affect the optical and electronic properties of both layers. In this work, we explore these effects in purified DWCNT samples by combining absorption, wavelength-dependent infrared fluorescence–excitation (PLE), and wavelength-dependent resonant Raman scattering (RRS) spectroscopy. Purified DWCNTs are obtained by careful solubilization that strictly avoids ultrasonication or by electronic-type sorting, both followed by a density gradient ultracentrifugation to remove unwanted SWCNTs that could obscure the DWCNT characterization. Chirality-dependent shifts of the radial breathing mode vibrational frequencies and transition energies of the inner and outer DWCNT walls with respect to their SWCNT analogues are determined by advanced two-dimensional fitting of RRS and PLE data of DWCNT and their reference SWCNT samples. This exhaustive data set verifies that fluorescence from the inner DWCNT walls of well-purified samples is severely quenched through efficient energy transfer from the inner to the outer DWCNT walls. Combined analysis of the PLE and RRS results further reveals that this transfer is dependent on the inner and outer wall chirality, and we identify the specific combinations dominant in our DWCNT samples. These obtained results demonstrate the necessity and value of a combined structural characterization approach including PLE and RRS spectroscopy for bulk DWCNT samples.

Acknowledgments We thank the participants of the FPF meetings and the Snowmass working groups for discussions that have contributed both directly and indirectly to this study. We gratefully acknowledge the invaluable support of the CERN Physics Beyond Colliders study group and the work of CERN technical teams related to civil engineering studies (SCE-DOD), safety discussions (HSE-OHS, HSE-RP, EP-DI-SO), integration (EN-ACE), and discussions on services (EN-CV, EN-EL, EN-AA) and simulations (SY-STI). L. A. Anchordoqui is supported by U.S. National Science Foundation (NSF) Grant PHY-2112527. A. Ariga is supported by JSPS, Japan KAKENHI Grant JP20K23373 and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant 101002690). T. Ariga acknowledges support from JSPS, Japan KAKENHI Grant JP19H01909. B. Batell is supported by U.S. Department of Energy (DOE) Grant DE–SC0007914 and by PITT PACC, USA. The work of J. Bramante is supported by NSERC, Canada. F. G. Celiberto acknowledges support from the INFN/NINPHA project, USA and thanks the Università degli Studi di Pavia, Italy for the warm hospitality. G. Chachamis is supported by the Fundação para a Ciência e a Tecnologia (Portugal) under project CERN/FIS-PAR/0024/2019 and contract ‘‘Investigador auxiliar FCT - individual Call, Portugal CEECIND/03216/2017 and acknowledges funding from the European Union’s Horizon 2020 research and innovation programme (Grant 824093). P. B. Denton is supported by DOE, USA Grant DE-SC0012704. Y. Du was supported by National Science Foundation of China (NSFC) Grants 12022514 and 11875003. The work of J. L. Feng is supported in part by NSF, USA Grants PHY- 1915005 and PHY-2111427, Simons Investigator Award, USA #376204, Simons Foundation, USA Grant 623683, and Heising-Simons Foundation, USA Grants 2019-1179 and 2020-1840. The work of M. Fieg, T. B. Smith, and Y.-D. Tsai is supported in part by NSF Grant PHY-1915005. M. Fucilla, M. M. A. Mohammed, and A. Papa acknowledge support from the INFN/QFT@COLLIDERS, Italy project. The work of M. V. Garzelli was supported in part by the Bundesministerium für Bildung und Forschung (BMBF), Germany. V. P. Goncalves was partially financed by the Brazilian funding agencies CNPq, FAPERGS, and INCT-FNA (process number 464898/2014-5). M. Guzzi is supported in part by NSF, USA Grants PHY- 1820818 and PHY-2112025. J. C. Helo acknowledges support from ANID FONDECYT-Chile Grant 1201673 and from ANID Millennium Science Initiative Program ICN2019 044. K. Jodłowski is supported by the National Science Centre, Poland, Grant 2015/18/A/ST2/00748. Ahmed Ismail and R. Mammen Abraham are supported by DOE, USA Grant DE-SC0016013. Ameen Ismail is supported by NSERC, Canada (reference number 557763) and by NSF, USA Grant PHY-2014071. Y. S. Jeong is supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT: Ministry of Science and ICT) (2021R1A2C1009296). The work of F. Kling is supported by DOE, USA Grant DE-AC02-76SF00515 and by the Deutsche Forschungsgemeinschaft under Germany’s Excellence Strategy – EXC 2121 Quantum Universe – 390833306. P. Nadolsky is supported by DOE, USA Grant DE-SC0010129. H. Otono acknowledges support from JSPS, Japan KAKENHI Grant JP20H01919. V. Pandey is supported by DOE, USA Grant DE-SC-0009824. M. H. Reno is supported in part by DOE, USA Grant DE-SC-0010113. The work of A. Ritz is supported by NSERC, Canada, Canada. The work of D. Sengupta is supported by NSF, USA Grant PHY-1915147. T. Sjöstrand is supported by Swedish Research Council Grant 2016-05996. D. Soldin acknowledges support from the NSF, USA Grant PHY-1913607. S. Trojanowski is supported by the grant ‘‘AstroCeNT: Particle Astrophysics Science and Technology Centre’’ carried out within the International Research Agendas programme of the Foundation for Polish Science financed by the European Union under the European Regional Development Fund, and by the Polish Ministry of Science and Higher Education through its scholarship for young and outstanding scientists (decision 1190/E-78/STYP/14/2019). K. Xie is supported by DOE, USA Grant DE-FG02-95ER40896, NSF, USA Grant PHY- 1820760, and in part by PITT PACC. Parts of this work have been supported by Fermi Research Alliance, LLC, USA under Contract DE-AC02-07CH11359 with the DOE., The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics., ANID FONDECYT-Chile 1201673, Fermi Research Alliance DE-AC02-07CH11359, HSE-OHS, HSE-RP, NINPHA, PITT PACC, SY-STI, National Science Foundation PHY-2112527, U.S. Department of Energy DE–SC0007914, Simons Foundation 376204, 623683, Fuel Cell Technologies Program 824093, DE-SC0012704, Horizon 2020 Framework Programme, First Peoples Fund, Heising-Simons Foundation 2019-1179, 2020-1840, Natural Sciences and Engineering Research Council of Canada, European Commission, European Research Council, Deutsche Forschungsgemeinschaft 390833306, DE-SC-0009824, DE-SC-0010113, DE-SC0010129, JP20H01919, PHY-1915147, Japan Society for the Promotion of Science JP20K23373, National Natural Science Foundation of China 11875003, 12022514, PHY-1915005, PHY-2111427, Fundação para a Ciência e a Tecnologia CERN/FIS-PAR/0024/2019, Bundesministerium für Bildung und Forschung, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Ministry of Science, ICT and Future Planning 2021R1A2C1009296, DE-AC02-76SF00515, National Research Foundation of Korea, Instituto Nazionale di Fisica Nucleare, Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, Narodowe Centrum Nauki 2015/18/A/ST2/00748, 557763, DE-SC0016013, PHY-2014071, Vetenskapsrådet 2016-05996, PHY-1913607, Ministerstwo Edukacji i Nauki 1190/E-78/STYP/14/2019, DE-FG02-95ER40896, PHY-1820760, Università degli Studi di Pavia, Horizon 2020 101002690, JP19H01909, European Regional Development Fund, Instituto Nacional de Ciência e Tecnologia: Física Nuclear e Aplicações 464898/2014-5, PHY-1820818, PHY-2112025, Agencia Nacional de Investigación y Desarrollo ICN2019 044

The last few years have seen an explosion of interest in hydrodynamic effects in interacting electron systems in ultra-pure materials. One such material, graphene, is not only an excellent platform for the experimental realization of the hydrodynamic flow of electrons, but also allows for a controlled derivation of the hydrodynamic equations on the basis of kinetic theory. The resulting hydrodynamic theory of electronic transport in graphene yields quantitative predictions for experimentally relevant quantities, e.g. viscosity, electrical conductivity, etc. Here I review recent theoretical advances in the field, compare the hydrodynamic theory of charge carriers in graphene with relativistic hydrodynamics and recent experiments, and discuss applications of hydrodynamic approach to novel materials beyond graphene., Invited review for La Rivista del Nuovo Cimento published online as an Open Source paper. Automated arXiv formatting is somewhat incompatible with the Springer style file, specifically, some hyperlinks might be broken. For a properly formatted file please follow the DOI link

Antimony triselenide (Sb2Se3) is one of the most promising absorber material choices among the inorganic semiconductors that has attracted much attention today. However, highest recorded efficiencies for Sb2Se3 solar cells are still lower than ideal. Exploring antimony selenosulfide (Sb-2(SxSe1-x)(3)) to increase device performance is one option because some features of alloyed Sb-2(SxSe1-x)(3) depend on composition such as bandgap and band position. In this study, two-step process was used to grow Sb-2(SxSe1-x)(3) thin films. In the first stage, Sb2Se3 thin films were deposited on soda lime glass substrates using direct current magnetron sputtering technique. In the second stage, Sb2Se3 thin films were exposed to sulfurization process in a quartz ampoule to obtain Sb-2(SxSe1-x)(3) thin films. Characterization results showed that morphological, optical, and structural properties of Sb-2(SxSe1-x)(3) thin films grown by presented method were highly dependent on amount of sulfur in the films. By the adjustment of the S/S + Se atomic ratio, Sb-2(SxSe1-x)(3) absorber materials with suitable bandgap, favorable orientation and compact morphology can be obtained for photovoltaic applications.

We show by embodying the Einstein equivalence principle - local Poincar\'{e} invariance - and general covariance in quantum theory that wave-function spreading rules out the universality of free fall, i.e. the free-fall trajectory of a quantum (test) particle depends on its internal properties. We provide a quantitative estimate of the free-fall non-universality in terms of the E\"{o}tv\"{o}s parameter, which turns out to be measurable in atom interferometry., Comment: typos fixed, published version

Quantum chromodynamics (QCD) describes how mass is created at the quark level. This mechanism is special because the binding of quarks does not result in a mass loss or a release of energy, as in the case of the nuclear mass defect. Rather, mass is created by the binding of quarks. To achieve this binding, energy must be expended. At the same time, however, quarks are firmly bound to each other. Several authors have shown that the masses of the elementary particles as determined by means of QCD agree quite well with the experimentally determined values. In the following, superfine adjustment of the masses of the charged elementary particles is shown to be possible by considering the mass defect in terms of the mass-charge binding energy. &nbsp

The flow of a compressible fluid with slip through a cylinder with an asymmetric local constriction has been considered both numerically, as well as analytically. For the numerical work, a particle-based method whose dynamics is governed by the multiparticle collision (MPC) rule has been used together with a generalized boundary condition that allows for slip at the wall. Since it is well known that an MPC system corresponds to an ideal gas and behaves like a compressible, viscous flow on average, an approximate analytical solution has been derived from the compressible Navier–Stokes equations of motion coupled to an ideal gas equation of state using the Karman–Pohlhausen method. The constriction is assumed to have a polynomial form, and the location of maximum constriction is varied throughout the constricted portion of the cylinder. Results for centerline densities and centerline velocities have been compared for various Reynolds numbers, Mach numbers, wall slip values and flow geometries.

The analysis of a previous paper, in which it was shown that the energy for the Aharonov-Bohm effect could be traced to the interaction energy between the magnetic field of the electron and the background magnetic field, is extended to cover the case in which the magnetic field of the electron is shielded from the background magnetic field by superconducting material. The paradox that arises from the fact that such a shielding would apparently preclude the possibility of an interaction energy is resolved and, within the limits of the ideal situation considered, the observed experimental result is derived., Published version: Foundations of Physics, Vol. 23 (1993) 703-709 doi: 10.1007/BF01883804 arXiv-ed February 18, 1993 ; \LaTeX-ed May 1, 2023 Uploaded to arXiv to help researchers with limited library facilities

The crystal structure of a solid largely dictates its electronic, optical and mechanical properties. Indeed, much of the exploration of quantum materials in recent years including the discovery of new phases and phenomena in correlated, topological and two-dimensional materials—has been based on the ability to rationally control crystal structures through materials synthesis, strain engineering or heterostructuring of van der Waals bonded materials. These static approaches, while enormously powerful, are limited by thermodynamic and elastic constraints. An emerging avenue of study has focused on extending such structural control to the dynamical regime by using resonant laser pulses to drive vibrational modes in a crystal. This paradigm of ‘nonlinear phononics’ provides a basis for rationally designing the structure and symmetry of crystals with light, allowing for the manipulation of functional properties at high speed and, in many instances, beyond what may be possible in equilibrium. Here we provide an overview of the developments in this field, discussing the theory, applications and future prospects of optical crystal structure engineering. The interaction between light and the crystal lattice of a quantum material can modify its properties. Utilizing nonlinear interactions allows this to be done in a controlled way to design specific non-equilibrium functionalities.

Unsteady, 3D particle tracking velocimetry (PTV) data are applied as an inlet boundary condition in a direct numerical simulation (DNS). The considered flow case is a zero pressure gradient (ZPG) turbulent boundary layer (TBL) flow over a flat plate. The study investigates the agreement between the experimentally measured flow field and its simulated counterpart with a hybrid 3D inlet region. The DNS field inherits a diminishing contribution from the experimental field within the 3D inlet region, after which it is free to spatially evolve. Since the measurement does not necessarily provide a spectrally complete description of the turbulent field, the spectral recovery of the flow field is analyzed as the TBL evolves. The study summarizes the pre-processing methodology used to bring the experimental data into a form usable by the DNS as well as the numerical method used for simulation. Spectral and mean flow analysis of the DNS results show that turbulent structures with a characteristic length on the order of one average tracer particle nearest neighbor radius r¯NN or greater are well reproduced and stay correlated to the experimental field downstream of the hybrid inlet. For turbulent scales smaller than r¯NN, where experimental data are sparse, a relatively quick redevelopment of previously unresolved turbulent energy is seen. The results of the study indicate applicability of the approach to future DNS studies in which specific upstream or far field boundary conditions (BCs) are required and may provide the utility of decreasing high initialization costs associated with conventional inlet BCs., Deutsche Forschungsgemeinschaft, Projekt DEAL

A model of spacetime is presented. It has an extension to five dimensions, and in five dimensions the geometry is the dual of the Euclidean geometry w.r.t. an arbitrary positive-definite metric. Dually flat geometries are well-known in the context of information geometry. The present work explores their role in describing the geometry of spacetime. It is shown that the positive-definite metric with its flat 5-d connection can coexist with a pseudometric for which the connection is that of Levi–Civita. The 4-d geodesics are characterized by five conserved quantities, one of which can be chosen freely and is taken equal to zero in the present work. An explicit expression for the parallel transport operators is obtained. It is used to construct a pseudometric for spacetime by choosing an arbitrary possibly degenerate inner product in the tangent space of a reference point, for instance, that of Minkowski. By parallel transport, one obtains a pseudometric for spacetime, the metric connection of which extends to a 5-d connection with vanishing curvature tensor. The de Sitter space is considered as an example.

Radiography is a common imaging method for non-destructive object inspection. Processing radiographs to detect defects is, however, challenging, especially if the defect type and location are unknown. In other fields, autoencoders (AE) have been largely studied for anomaly detection. While their performance for defect detection has shown promise, many solutions are not demonstrated to be defect-independent. In this work, we introduce a radiography-based anomaly detection method that first computes the AE prediction error from an input radiograph to enhance the detectability of defects. Subsequently, the probability of the imaged object being defective is predicted by a convolutional classification network. Results on simulated data demonstrate that this method succeeds in distinguishing between defective and nondefective objects, with accuracy (which calculates how often the predictions are equal to the labels) >94% and precision (which is the ratio between the true positives and the total predicted positive) >90%, even for defects unseen during the training stage. Our classification network showed high robustness to noise (with signal-to-noise-ratio (SNR) of 20 dB), and accuracy on noisy data >90% and precision >86%. Since our network workflow does not require image registration for defect detection, the proposed solution is therefore independent of the orientation and position of the object during the scan.

Although nanochannels in tortuous shape exhibit unusual transportational characteristics, the traditional theoretical analysis of nanofluidics in such kinds of systems remains challenging, partly due to their complicated boundary description. In this paper, by developing a curvilinear coordinate system for such tortuous nanochannels, we solve the electrostatic Poisson–Boltzmann equation analytically for a two-dimensional nanochannel, with its effectiveness confirmed through numerical calculation. The influences of the geometric profile on the distribution of electric potential, ionic concentration, and surface charge on channel walls are quantitatively evaluated in a facilitated way in terms of the curvilinear coordinates introduced. Such a technique can be widely applied to many nanofluidic systems in curved channels.

The visual arts are rooted in the life of the wider community and may lack explicit medical physics reference. Nevertheless, they can be influential and can illustrate, communicate, and inform. They may also inspire, challenge, heal, give pleasure, help put one's life in perspective and enrich the experience of being a practicing scientist working in medical physics. Eighteen works from 12 artists are presented. They are a convenience sample from the author's experience. Two (Irish), though less well known, speak powerfully to scientists. Two are of the eighteenth century. The remaining works are modern from Europe, North America and Japan. All inform and challenge our behaviour as medical physicists. Headings guiding the paper address: historical perspectives; similarities of method between science and the arts; the hand as special expressions of being human; communicating science; science and a sense of wonder; borders to science; and the importance of a quiet, still, reflective approach. The author's experience complements observations published by others. The artworks described delight and are an able ally in validating a life spent in science. They refresh it and are accessible to those willing to take a risk on the approach, with sensibility and an openness. The impact of art on science and medicine is also visible in under explored institutional art collections such as those housed at the IAEA in Vienna or WHO in Geneva.

In this article, we consider a known charged isotropic Durgapal IV solution and extend it to its anisotropic version using gravitational decoupling by means of extended geometric deformation (EGD) approach, which provides a more generic way for the decoupling of gravitational sources. Following this approach, we employ linear transformation on both metric potentials and split the original set of field equations into two subsystems. The first subsystem corresponds to charged isotropic fluid while the second one is related to the additional source, crucial for anisotropy. The isotropic one is specified through metric functions of known charged isotropic solution, while the solution of second sector is determined by considering two different constraints on additional source Θ a b , i.e., mimicking of isotropic pressure and a linear equation of state which relating Θ 0 0 and Θ 1 1 . The matching conditions at the stellar surface are discussed in detail, where outer geometry is represented by Reissner–Nordstrom solution. We discuss the physical properties of the stellar model in comparison with its uncharged anisotropic analogue, which is provided in Appendix. Physical analysis is carried out using different physical indicators including energy conditions, equilibrium equation, casualty condition, Herrera’s cracking concept, adiabatic index, compactness and surface redshift for compact star PSR J 1416-2230. We find that anisotropic stellar model is stable for larger range of γ (coupling constant) in the presence of electric charge and the effects of anisotropy are diminished near stellar surface.

A molecular spintronics device is considered as a highly promising candidate for the quantum hardware in the field of practical quantum information applications. Within this field, local objects always obey the Coulomb blockade effect, where electrons occupy molecular orbitals monotonically in a step-like manner as the gate voltage sweeps. Herein, based on a single-molecule transistor in an external magnetic field, we predict that the charge occupation of both spin channels may show nonmonotonic filling, characterized by a spin-sensitive charge oscillation, contravening the standard Coulomb blockade behavior. We attribute this nonmonotonicity to the competition among the Zeeman effect, the many-body effect, and the symmetry of the quantum states. To obtain significant oscillations, strong electron–electron interaction and low temperature are prerequisites. We demonstrate that the oscillation goes against the spin-polarized transport, and for appropriate parameters, the transistor may act as a perfect electronically-manipulable bidirectional molecular spintronics device. To implement such an ideal, the state-of-the-art numerical renormalization group method is adopted, and an experimental proposal to test these predictions is suggested.

The double entropic stochastic resonance (DSR) phenomenon for a Brown particle moving in a confined geometry driven by a time-dependent force in the declining direction subject to additive master noise and recycled noise is investigated in this paper. Under the adiabatic approximation condition, based on two-state theory and linear response theory, the expression for the system linear response (LR) is derived. Stochastic resonance (SR) and periodic SR behavior is observed when the LR changes with the feedback coefficient and with the time-delay of the recycled noise. DSR phenomenon appears when the LR varies with the constant component and with the fluctuation noise intensity of the force in the declining direction. Tradition SR occurs on the curve of the LR when the LR varies with the intensity of the master noise. The non-monotonous effect of the parameters of the confined structure on the LR is discussed.

In this work, we have developed the time conformal slowly rotating Kerr black hole using the approximate Noether symmetry approach. It is found that the slowly rotating Kerr black hole admits time conformal factor e ϵ f ( t ) , where ϵ is very small perturbation and f ( t ) is an arbitrary function of time. We have obtained the numerical solutions of geodesics for lowly rotating Kerr black hole and time conformal slowly rotating Kerr black hole. We have discussed the neutral and charged particle dynamics moving around time conformal slowly rotating Kerr black hole in the absence/presence of magnetic field. Moreover, we have analyzed graphically the behavior of effective force, effective potential and escape velocity of particles in the absence/presence of magnetic field near the event horizon. We have examined the conditions under which particle can escape from the surrounding of black hole after colliding with another particle. We have found the unstable orbits of particles near event horizon due to the effect of magnetic field and angular momentum.

Stochastic resonance of an asymmetric tristable system driven by a periodic forcing and cross-correlated Ornstein-Uhlenbeck (O-U) noise is investigated. An approximate Fokker-Planck Equation for an asymmetric tristable system driven by a periodic forcing and cross-correlated O-U noise is derived in the adiabatic limit by using the unified colored-noise approximation method and the stochastic equivalent rules. Afterwards, the expression for spectral amplification (SA), the stationary probability density function (PDF) and the mean first passage time (MFPT) are derived. By considering the influence of asymmetric potential function and cross-correlated noise, the phenomenon of noise enhancing stability (NES) and stochastic resonance (SR) can be found. It can also be found that the response of the tristable system can be effectively improved by properly selecting the relevant noise intensity and the asymmetric constant. This proves the excellent performance of the system, and provides a good theoretical support for practical engineering application.

An extended FitzHugh–Nagumo model is developed to model the synaptic coupling of neurons and the associated dynamics. The neurons are coupled via chemical synapses, which can excite or inhibit the postsynaptic neuron. The neurotransmitter-receptor dynamics is governed with a gating dynamic, which allows for the distinction between fast and slow synapses. Detailed nonlinear dynamics analysis are performed for simple neural motifs of a self-synapsed neuron and two synaptically coupled neurons for the instabilities that lead to neural oscillations, and the associated phase diagrams are obtained. Interesting dynamics such as synchronization of fast and slow firing neurons, frequency enhancement, quiescent neurons coupled to oscillators, chaotic spiking, and periodic bursting are found.

In this paper, we are interested to explore stable configurations of $d$-dimensional gravastars constructed from the interior $d$-dimensional de Sitter and exterior $d$-dimensional Schwarzschild/Reissner-Nordstr\"om (de Sitter) black holes through cut and paste approach. We consider the linearized radial perturbation preserving the original symmetries to explore their stability by using three different types of matter distributions. The resulting frameworks represent unstable structures for barotropic, Chaplygin, and phantomlike models for every considered choice of exterior geometries. However, matter contents with variable equations of state have a remarkable role to maintain the stability of gravastars. We conclude that stable structures of gravastars are obtained only for generalized variable models with exterior $d$-dimensional Schwarzschild/Reissner-Nordstr\"om-de Sitter black holes., Comment: 21 pages, 12 figures, to appear in Chinese J. Physics

In this paper, we study the dynamics of a three-species food chain model with two delays duo to fear. First we discuss the permanence of this delayed model, then we discuss dynamics under six cases: (1) τ 1 = τ 2 = 0 , (2) τ 1 > 0 , τ 2 = 0 , (3) τ 2 > 0 , τ 1 = 0 , (4) τ 1 = τ 2 > 0 , (5) τ 1 ∈ ( 0 , τ 10 ) , τ 2 > 0 , (6) τ 2 ∈ ( 0 , τ 20 ) , τ 1 > 0 . We shall study the Hopf bifurcation about case (5) by center manifold theorem and normal form. At last we shall give simulations which reveal the influence of delays and fear on the dynamics of this predator–prey system.

In this paper, we present a detailed analytical computation of the triple differential cross sections, in the first Born approximation, for the relativistic electron-impact ionization of hydrogen atom in the metastable 2S-state in the symmetric and asymmetric coplanar geometries. The process is investigated by using the relativistic Dirac-formalism where the effects of spin and relativity are taken into account. It is shown that the nonrelativistic limit is accurately reproduced when applying low incident kinetic energies. At high energies, relativistic and spin effects are found to significantly affect the triple differential cross sections. The numerical results obtained for the triple differential cross section are compared with some other theoretical results in the nonrelativistic regime for asymmetric coplanar geometry. For this particular process and in the absence of any experimental data and theoretical models at high energies for the triple differential cross sections, the results of our calculated relativistic total cross section are compared with available theoretical and experimental results. We hope that the present study will provide significant contribution to future experiments.

In this paper, we explore analytic solutions of self-gravitating celestial objects known as gravastars in energy–momentum squared gravity. A gravastar is referred as an alternative model to a black hole which is exhibited by three different regions, i.e., the intermediate shell, interior, and exterior regions. We examine these regions for a particular model of this gravity with conformal motion. The field equations are developed with perfect fluid for a spherically symmetric spacetime. The mathematical formulation for these domains is expressed by using a barotropic equation of state. We use Israel matching conditions for the smooth joining of outer and inner spacetimes. We analyze various physical features of gravastars along with the thickness of the shell, i.e., equation of state parameter, proper length, entropy and energy. These characteristics represent physically consistent non-singular solutions.

A systematic theoretical investigation has been carried out in order to explore the propagation of both linear and nonlinear dust acoustic waves (DAWs) in a collisional magnetized warm dusty plasma in the presence of nonextensive electrons and ions. A linear dispersion relation is analyzed to show that the wave frequencies of both parallel and perpendicular modes are modified by the relevant plasma parameters. The standard reductive perturbative technique leads to a Korteweg–de Vries equation with a linear damping term for the propagation dynamics of the finite amplitude waves in warm dusty plasma. It is found that the dust-neutral collision induced dissipation is responsible for the linear damping. The analysis reveals that DAW propagates in the form of a weakly dissipative compressive/rarefactive solitons and the nonlinear excitations are significantly influenced by different plasma parameters, such as dust concentration, nonextensivity, external magnetic field strength, and dust-neutral collisionality. The present results can be relevant to the DAWs in some astrophysical plasma environments, such as Saturn’s rings, interstellar dusty clouds, etc.

Based on three-wave method, abundant nonautonomous solutions with different wave structures of a 3D variable-coefficient generalized shallow water wave equation are presented. In this situation the basic configurations (characteristic, amplitude, and speed) of the nonautonomous waves mutate with time due to the effect of nonlinearity and dispersion. Discussions indicate the interaction between lump wave and a pair of resonance stripe solitons solutions, the interaction between lump wave and periodic wave solutions, and the breather-type periodic soliton solutions. The dynamic properties of the obtained solutions are demonstrated and analyzed graphically for different choices of the arbitrary functions in these solutions.

In this work we study a non-flat Friedmann-Robertson-Walker universe filled with a pressure-less dark matter (DM) and Barrow holographic dark energy (BHDE) whose IR cutoff is the apparent horizon. Among various DE models, (BHDE) model shows the dynamical enthusiasm to discuss the universe's transition phase. According to the new research, the universe transitioned smoothly from a decelerated to an accelerated period of expansion in the recent past. We exhibit that the development of $q$ relies upon the type of spatial curvature. Here we study the equation of state (EoS) parameter for the BHDE model to determine the cosmological evolution for the non-flat universe. The (EoS) parameter and the deceleration parameter (DP) shows a satisfactory behaviour, it does not cross the the phantom line. We also plot the statefinder diagram to characterize the properties of the BHDE model by taking distinct values of barrow exponent $\triangle$. Moreover, we likewise noticed the BHDE model in the $(\omega_{D}-\omega_{D}^{'})$ plane, which can furnish us with a valuable, powerful finding to the mathematical determination of the statefinder. In the statefinder trajectory, this model was found to be able to reach the $\Lambda CDM$ fixed point., Comment: 19 pages, 21 figures

In this paper, a unique one-dimensional double anti-PT-symmetric ring optical waveguide network (1D DAPTSROWN) is designed whose refractive index satisfies n ( x ) = − n ∗ ( − x ) . The extraordinary optical characteristics of the network are studied by means of the generalized Floquet-Bloch theorem, three-material network equation and generalized eigenfunction method. Due to the physical difference between the anti-PT-symmetric and PT-symmetric optical waveguide networks, the previous methond of the PT-symmetric optical waveguide network is not applicable to the anti-PT-symmetric optical waveguide network designed in this paper. Thus, based on the previous method and the network equation, we propose a connection function to identify the extremum mode points in the anti-PT-symmetric optical waveguide network. At the extremum mode point, the optical waveguide network can produce extraordinary ultra-strong transmission, ultra-strong reflection, and ultra-strong photonic localizations. The corresponding calculated values in this paper arrives at 1 0 28 , which is much larger than 1 0 12 (the best result reported previously). This shows that the anti-PT-symmetric network may have potential in applications in designing optical filters, optical amplifiers and so on.

In principle, this paper suggests powerful laser technology as a promising instrument that can be experimentally useful to control the lifetime and branching ratio for an unstable particle decay. In a recent paper [ arXiv:2101.00224 ], we calculated theoretically the W − -boson leptonic decay ( W − → l − ν l ) in the presence of a circularly polarized laser and we showed that the laser significantly contributed to the diminution of the leptonic decay rate. In this paper, as a continuation of the previous one, we mainly deal with the theoretical calculation of the W − -boson hadronic decay ( W − → q q ′ ) and we combine the analytical results obtained in both papers to examine the effect of an intense laser, in terms of its field strength and frequency, on the three measurable quantities in W − -boson decay (total decay rate, lifetime and branching ratios). It was found that the laser has notably contributed to the reduction of the total decay rate leading to a longer lifetime. Most importantly, the two branching ratios (one for leptons and the other for hadrons) are affected (increased or decreased) by the presence of a strong external electromagnetic field. Combined together, these two complementary works may provide an in-depth and comprehensive study that would be useful for any experimental investigation in the future.

We show that the matter-antimatter asymmetry in the present-day universe is mainly due to the highly suppressed detection probability for the primordial antimatter, which is a direct result of the Dirac-Feynman-Stueckelberg interpretation of antimatter and the extremely time asymmetric expansion of the primordial universe.

In the framework of linear elasticity, the longitudinal acousto-elastic time-averaged radiation force exerted on a cylindrical fluid-filled inclusion of arbitrary size embedded in an unbounded elastic matrix is derived based upon the integration of the time-averaged power flow density over a surface enclosing the particle. The cases of compressional and shear plane progressive elastic waves are considered. Mathematical expressions for the longitudinal radiation force efficiencies are derived and cast in exact series expansions in cylindrical coordinates. The elastic scattering solution, which is utilized to derive the acousto-elastic radiation force expressions, is determined. The analytical expressions for the acousto-elastic radiation force clearly show the contributions related to mode conversion P → S for the incident compressional waves, and S → P for shear wave incidence (where P and S denote, respectively, the compressional and shear waves). Another method, based on the extinction energy efficiency and the scattering asymmetry parameter, is shown to provide the same exact expression of the force obtained based upon the power flow density formalism. Computations for the dimensionless radiation force efficiencies and their cross-polarized (P → S and S → P) components demonstrate that mode conversion contributes negatively, positively or neutrally depending on the mass density of the particle, its size, and the properties of the surrounding elastic medium. In addition, elastic resonances are manifested in the acousto-elastic radiation force plots. This analysis provides a rigorous exact formalism using exact partial-waves series to compute the acousto-elastic radiation forces of compressional or shear waves on an elongated cylindrical particle encased in a linear elastic medium. The analytical series expressions and numerical predictions can be used as a priori information in optimizing and designing acousto-elastic radiation force experiments in materials science, elastography, vibro-acoustography, nondestructive evaluation, and the activation/excitation of a fluid cylinder embedded in an elastic medium, to name a few examples. The electromagnetic/optical analogue for materials exhibiting circular dichroism is also noted.

In the centre of mass frame, we have studied theoretically the Z -boson resonant production in the presence of an intense laser field via the weak process e + e − → μ + μ − . Dressing the incident particles by a Circularly Polarized laser field (CP-laser field), at the first step, shows that for a given laser field’s parameters, the Z - boson cross section decreases by several orders of magnitude. We have compared the Total Cross Section (TCS) obtained by using the scattering matrix method with that given by the Breit-Wigner approach in the presence of a CP-laser field and the results are found to be very consistent. This result indicates that Breit-Wigner formula is valid not only for the laser-free process but also in the presence of a CP-laser field. The dependence of the laser-assisted differential cross section on the Centre of Mass Energy (CME) for different scattering angles proves that it reaches its maximum for small and high scattering angles. At the next step and by dressing both incident and scattered particles, we have shown that the CP-laser field largely affects the TCS, especially when its strength reaches 1 0 9 V . c m − 1 . This result is interpreted by the fact that heavy interacting particles require high laser field intensities to affect the collision’s cross section.

In this paper, we focused on the study of anisotropic strange stars with anisotropic matter distribution in the framework of f ( T , T ) = α T ( r ) 2 + β T ( r ) model, where α , β are arbitrary constants, T and T represent the torsion scalar and trace of energy–momentum tensor, respectively. This model has interesting cosmological properties, in addition to providing an effective dark energy sector explanation (Harko et al., 2014). In order to achieve our goal, we considered the Krori-Barua space–time and utilize the off-diagonal tetrad components for deriving the corresponding set of field equations. We calculate the relation for the evaluation of effective density, effective radial and tangential pressure using the EoS of strange star i.e., MIT bag model p r ( r ) = 1 3 [ ρ ( r ) − 4 B g ] . The unknown constants appearing in the solution have been evaluated by using the conventional matching of interior and exterior space time. To check the feasibility of our proposed model we discuss the anisotropy, energy condition, TOV forces, abreu condition, EoS parameters, adiabatic index, mass function, compactness and redshift for different compact stars models namely, P S R J 1416 − 2230 , 4 U 1608 − 52 , C e n X − 3 , E X O 1785 − 248 and S M C X − 1 .

In this paper, the physical phenomena in fractional calculus of the space–time fractional Bi-Hamiltonian Boussinesq system involving the Riemann–Liouville derivatives is studied. The wave dispersion relationship in the linear form of the governing system is analyzed and then that relationship is used to obtain the velocity of the phase and group. Soliton solutions are developed using the fractional sub-equation method. The soliton solutions obtained in the form of trigonometry, hyperbolic and rational function illustrate that the approach of fractional sub-equation is very effective in evaluating the physical phenomena.

In this paper, we study optical bistability (OB) and optical multistability (OM) in a defect medium with a monolayer of graphene quantum system. The graphene quantum system interacts with two weak probe laser fields and an elliptical polarized coupling beam for adjusting the linear and nonlinear optical properties of defect layer. We find that by controlling the relative phase between applied lights and elliptical parameter of the coupling light, the enhanced Kerr nonlinearity with probe amplification can be obtained in resonance of probe light. Then we study the transmission and reflection coefficients of the incident lights for controlling the OB and OM features of transmitted and reflected light beams, respectively. Also, we discuss the thickness effect of the defect layer on the OB and OM properties and find that the switching from OB to OM or vice versa is possible. Moreover, we realize that by modifying the nonlinear properties of the defect medium, one can control the behaviors of the OB and OM, respectively.

Because of the rapid advancement of microdevices technologies, electroosmotic flow (EOF) has gotten a lot of coverage in recent years. EOF has a range of benefits over other micropumps, including the ability to create continuous pulse-free flows and elimination of moving parts. Our aim is to investigate the unsteady electroosmotic flow (EOF) of an electrolyte solution of generalized fractional second grade hybrid nanofluid (Cu-TiO 2 / Water) confined between vertical two coaxial tubes. The energy equation will be altered by the fractional Cattaneo model. The finite Hankel technique and Laplace transformation will be employed to acquire the solution of the mathematical model. Since obtaining the inversion of Laplace of the transformed functions in the closed-form is a challenging task, the numerical inversion algorithm will be used. The results showed that the hybrid nanofluid became more viscous with increasing the volume concentration which reduces the electroosmotic (EO) velocity and the flow rate. Moreover, the electroosmotic flow is boosted by the free convection force.

In this work, using a spherically symmetric metric, we investigate a minimally interacting holographic dark energy model within the framework of Saez-Ballester Theory. We predict that the dark energy component dominating the universe is of phantom type, which will lead the model universe to cosmic doomsday (big rip singularity). As big rip and holographic dark energy are incompatible with each other, we employ a higher dimensional scenario so that the cosmic doomsday is replaced by the de-Sitter phase. The model expands with a slow and uniform change of size during the early evolution, whereas the change becomes faster, agreeing with the present observation of the accelerated expansion. The present values of Hubble’s parameter and the dark energy EoS parameter are measured to be H = 67 and λ = − 1 . 00011 , which agree with the respective values H 0 = 67 . 36 ± 0 . 54 kms − 1 Mpc − 1 and λ = − 1 . 03 ± 0 . 03 of the most recent Planck 2018 result.

Unsteady convective flows, over an infinite, vertical, heated, circular cylinder is investigated by considering the generalized Fourier's law of the thermal process. The generalized constitutive equation of thermal flux is a partial fractional differential equation based on the generalized time-fractional derivative with Mittag-Leffler kernel, namely the generalized Atangana-Baleanu derivative. Closed forms of the analytical solutions for the temperature and velocity fields, expressed with Bessel and Struve functions, are determined using the Laplace transform and the Weber-Dirichlet transform. The ordinary case corresponding to classical Fourier's law is also obtained. Numerical simulations, obtained with the Mathcad software, are carried out and graphically illustrated to analyze the heat transfer and fluid motion. The influence of the fractional orders of the time-derivative and of the Prandtl and Grashof numbers on the fluid temperature and velocity is studied.

In this paper, we investigate a damped variable-coefficient fifth-order modified Korteweg–de Vries equation for the small-amplitude surface waves in a strait or large channel of slowly-varying depth and width and non-vanishing vorticity, in which α 1 ( t ) , β ( t ) and γ ( t ) are the dispersive, dissipative and line-damping coefficients, respectively, where t is the temporal variable. Bilinear forms, bilinear Backlund transformation and multi-soliton solutions are constructed via the Hirota bilinear method under some variable-coefficient constraints. Based on those multi-soliton solutions, multi-pole, breather and hybrid solutions are derived. Effects of α 1 ( t ) , β ( t ) and γ ( t ) on the solutions are discussed analytically and graphically. For the solitons, we find that α 1 ( t ) and β ( t ) are related to the velocities and characteristic lines, and the amplitudes depend on γ ( t ) . For the multi-pole and breather solutions, α 1 ( t ) and β ( t ) influence the center trajectories of the solutions, while γ ( t ) influences the amplitudes. Hybrid solutions composed of the breathers and solitons are worked out and discussed graphically.

The degree distribution of network nodes exhibits scale-free features, which is a universal phenomenon in natural and social networks. It is commonly believed that growth and linear preferential attachment are the evolutionary mechanisms of scaling laws. However, the underlying cause behind these mechanisms remains unknown. In this paper, we propose the concept of the topology state of network nodes, and then define the network homomorphism ratio. Combining the total energy of the network defined in previous studies, we systematically investigate the connection between these two quantities in preferential attachment growth networks. Our results show that under the thermodynamic limit condition, the emergence of the scaling laws of the preferential attachment growth network is dominated by two principles. One principle is that the homomorphism ratio gradually tends to zero as the network grows, and the other principle is that the total energy of the system is the lowest under the condition of satisfying principle one. Interestingly, these two principles of the network are similar to the arrangement rules of electrons outside the nucleus which dominated by the Pauli exclusion principle and the principle of minimum energy.

Starting from a 2 × 2 discrete matrix spectral problem, we construct an integrable lattice hierarchy associated with RTL + ( α ) system which is a one-parameter perturbation of the usual Toda lattice system describing the particle motion in a lattice. Based on the obtained RTL + ( α ) hierarchy, some integrable properties such as Hamiltonian structures, Liouville integrability and conservation laws are investigated. Furthermore, we establish the discrete N -fold Darboux transformation (DT) of RTL + ( α ) system. As applications of the obtained DT, multi-soliton solutions are derived on constant seed backgrounds, and discrete soliton propagation and elastic interaction structures are shown graphically and analyzed via asymptotic analysis. Numerical simulations are utilized to demonstrate the dynamical behaviors of such soliton solutions. Numerical results show that soliton evolutions are stable against a small noise. Results given in this paper might be helpful for understanding the propagation of nonlinear waves in soliton theory.