Search

The growing interaction between traditional knowledge and formal sciences emerges as a relevant field of research. In this perspective, the aim of this article is to investigate the intersections between Physics and traditional knowledge in the ceramics practices of Vila Cuera, in Bragan\c{c}a, state of Para. Using an ethnographic approach, complemented by qualitative analysis, we realize that ceramists use their sensitive intuition and, masterfully, apply thermodynamic principles in the production of handmade ceramics. The results highlight the value of Ethnophysics, underlining that, long before the formal structuring of science as we know it, traditional societies already practiced and understood natural phenomena in tune with contemporary physical principles. We conclude that there is an inherent link between Physics and traditional knowledge with regard to the traditional ceramics practice, grounded on empirical observations and ancestral wisdom, that dialogues with science in a complementary relationship. The study highlights the importance of valuing and recognizing the knowledge of traditional populations by highlighting the knowledge doings of cultures and institutionalized science., Comment: in Portuguese

In this paper, we show that a possible relationship between the Hubble-Lema\^{i}tre constant and the universe holographic complexity can be established in the context of a new proposal for the emergence of spacetime, according to which spacetime must emerge from quantum information encoded in quantum correlations without correlate. Such a bridge between the Hubble-Lema\^{i}tre constant and the universe holographic complexity can shed some light on the issue of the Hubble tension., Comment: Possible text overlap with arxiv 2205.09502 [gr-qc] by the same author

In this paper, we address the nature of spacetime in quantum gravity in light of a new version of the holographic principle that has established a relationship between string theory and polymer holonomy structures similar to Loop Quantum Cosmology spin networks. In front of the results found out, it is possible to argue that, for such a relationship to work, spacetime must be seen as emergent from a fundamental structure whose degrees of freedom correspond to quantum correlations only., Comment: Published in: Nucl.Phys.B 998 (2024) 116402. Possible text overlap with arxiv 2205.09502 [gr-qc] by the same author

In this work, we address the thermodynamical evolution of the universe in the context of Loop Quantum Cosmology by considering the conditions for the existence of a time arrow in this approach. We find out that, for the existence of a time arrow in our universe, in terms of its obedience to the Generalized Second Law of Thermodynamics, the initial state of the cosmos must correspond to a negative entropy one., Comment: 13 pages. Submitted to PLB

It is generally assumed that environmental noise arising from thermal fluctuations is detrimental to preserving coherence and entanglement in a quantum system. In the simplest sense, dephasing and decoherence are tied to energy fluctuations driven by coupling between the system and the normal modes of the bath. Here, we explore the role of noise correlation in an open-loop model quantum communication system whereby the ``sender'' and the ``receiver'' are subject to local environments with various degrees of correlation or anticorrelation. We introduce correlation within the spectral density by solving a multidimensional stochastic differential equations and introduce these into the Redfield equations of motion for the system density matrix. We find that correlation can enhance both the fidelity and purity of a maximally entangled (Bell) state. Moreover, by comparing the evolution of different initial Bell states, we show that one can effectively probe the correlation between two local environments. These observations may be useful in the design of high-fidelity quantum gates and communication protocols.

We present first results from a Positron Emission Tomography (PET) scanner demonstrator based on Resistive Plate Chambers and specialized for brain imaging. The device features a 30 cm wide cubic field-of-view and each detector comprises 40 gas gaps with 3D location of the interaction point of the photon. Besides other imagery, we show that the reconstructed image resolution, as evaluated by a hot-rod phantom, is sub-millimetric, which is beyond the state-of-the-art of the standard PET technology for this application.

Nonlinear Optical Spectroscopy is a well-developed field with theoretical and experimental advances that have aided multiple fields including chemistry, biology and physics. However, accurate quantum dynamical simulations based on model Hamiltonians are need to interpret the corresponding multi-dimensional spectral signals properly. In this article, we present the initial release of our code, QuDPy (quantum dynamics in python) which addresses the need for a robust numerical platform for performing quantum dynamics simulations based on model systems, including open quantum systems. An important feature of our approach is that one can specify various high-order optical response pathways in the form of double-sided Feynman diagrams via a straightforward input syntax that specifies the time-ordering of ket-sided or bra-sided optical interactions acting upon the time-evolving density matrix of the system. We use the quantum dynamics capabilities of QuTip for simulating the spectral response of complex systems to compute essentially any n-th-order optical response of the model system. We provide a series of example calculations to illustrate the utility of our approach.

We have previously demonstrated that in the context of two-dimensional (2D) coherent electronic spectroscopy measured by phase modulation and phase-sensitive detection, an \emph{incoherent} nonlinear response, due to pairs of photoexcitations produced via linear excitation pathways, contribute to the measured signal as unexpected background [Gr\'egoire et al., J.\ Chem.\ Phys. \textbf{147}, 114201 (2017)]. Here, we simulate the effect of such incoherent population mixing in the photocurrent signal collected from a GaAs solar cell by acting externally on the transimpedance amplifier circuit used for phase-sensitive detection, and we identify an effective strategy to recognize the presence of incoherent population mixing in 2D data. While we find that incoherent mixing is reflected by cross-talk between the linear amplitude at the two time-delay variables in the four-pulse excitation sequence, we do not observe any strict phase correlations between the coherent and incoherent contributions, as expected from modelling of a simple system., Comment: Resubmitted to the Journal of Chemical Physics

We review our recent quantum stochastic model for spectroscopic lineshapes in the presence of a co-evolving and non-stationary background population of excitations. Starting from a field theory description for interacting bosonic excitons, we derive a reduced model whereby optical excitons are coupled to an incoherent background via scattering as mediated by their screened Coulomb coupling. The Heisenberg equations of motion for the optical excitons are then driven by an auxiliary stochastic population variable, which we take to be the solution of an Ornstein-Uhlenbeck process. Here we discuss an overview of the theoretical techniques we have developed as applied to predicting coherent non-linear spectroscopic signals. We show how direct (Coulomb) and exchange coupling to the bath give rise to distinct spectral signatures and discuss mathematical limits on inverting spectral signatures to extract the background density of states., Comment: arXiv admin note: substantial text overlap with arXiv:2008.08211

A new kind of duality has been proposed by Carr related to the quantum description of black holes, the so-called Compton/Schwarzschild duality \cite{Carr:2015nqa}. In this context, a new form for a Generalized Uncertainty Principle has arisen, which must bring us an interesting new route to a quantum description of spacetime. In the present paper, we shall investigate the consequences of the Compton/Schwarzschild duality to black hole entropy. The results found out reinforce an interesting perspective on the relationship between black holes and quantum information theory that has been recently proposed in the literature: that black hole entropy can assume negative values at the final stage of black hole evaporation. Consequently, in the context of the quantum corrections to gravity proposed by the Compton/Schwarschild duality, the final state of a black hole might correspond to a quantum entangled state, in the place of a remnant.

Spectral line-shapes provide a window into the local environment coupled to a quantum transition in the condensed phase. In this paper, we build upon a stochastic model to account for non-stationary background processes produced by broad-band pulsed laser stimulation. In particular, we consider the contribution of pair-fluctuations arising from the full bosonic many-body Hamiltonian within a mean-field approximation, treating the coupling to the system as a stochastic noise term. Using the It{\^o} transformation, we consider two limiting cases for our model which lead to a connection between the observed spectral fluctuations and the spectral density of the environment. In the first case, we consider a Brownian environment and show that this produces spectral dynamics that relax to form dressed excitonic states and recover an Anderson-Kubo-like form for the spectral correlations. In the second case, we assume that the spectrum is Anderson-Kubo like, and invert to determine the corresponding background. Using the Jensen inequality, we obtain an upper limit for the spectral density for the background. The results presented here provide the technical tools for applying the stochastic model to a broad range of problems., Comment: Replaces previous incorrect posting. In press, J. Chem. Phys

The lineshape of spectroscopic transitions offer windows into the local environment of a system. Here, we present a novel approach for connecting the lineshape of a molecular exciton to finite-temperature lattice vibrations within the context of the Davydov soliton model (A. S. Davydov and N. I. Kislukha, Phys. Stat. Sol. {\bf 59},465(1973)). Our results are based upon a numerically exact, self-consistent treatment of the model in which thermal effects are introduced as fluctuations about the zero-temperature localized soliton state. We find that both the energy fluctuations and the localization can be described in terms of a parameter-free, reduced description by introducing a critical temperature below which exciton self-trapping is expected to be stable. Above this temperature, the self-consistent ansatz relating the lattice distortion to the exciton wavefunction breaks down. Our theoretical model coorelates well with both experimental observations on molecular J-aggregate and resolves one of the critical issues concerning the finite temperture stability of soliton states in alpha-helices and protein peptide chains.

In the context of a nonequilibrium statistical thermodynamics, based on a nonequilibrium statistical ensemble formalism, a generalized hydrodynamics of fluids under driven flow and shear stress is derived. At the thermodynamic level, the nonequilibrium equations of state are derived, which are coupled to the evolution of the basic variables that describe the hydrodynamic motion in such a system. Generalized diffusion-advection and Maxwell-Cattaneo advection equations are obtained in appropriate limiting situations. This nonlinear higher-order hydrodynamics is applied, in an illustration, to the case of a dilute solution of Brownian particles in nonequilibrium conditions and flowing in a solvent acting as a thermal bath. This is done in the framework of such generalized hydrodynamics but truncated up to a second order.