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We report investigations of the structural, magnetic, electrical transport and thermal properties of five compositions of the metallic perovskite GdRh$_3$C$_{1-x}$B$_x$ ($0.00 \le x \le 1.00$). Our results show that all the five compositions undergo magnetic ordering at low temperatures, but the nature of the ordered state is significantly different in the carbon- and the boron-rich compositions, where the former shows signatures of an amplitude-modulated magnetic structure and the latter exhibits evidences of an equal-moment incommensurate antiferromagnetic ordering. We also observe a remarkable field-dependent evolution of conduction carrier polarization in the compositionally disordered compounds. The outcomes indicate that this system is energetically situated in proximity to a magnetic instability where small variations in the control parameter(s), such as lattice constant and/or electron density, lead to considerably different ground states., Comment: 10 pages and 9 figures

We consider four-dimensional chiral gauge theories defined over a spacetime manifold with topology $\mathbb{R}^3 \times S^1$ and periodic boundary conditions over the compact dimension. The effective gauge-field action is calculated for Abelian $U(1)$ gauge fields $A_{\mu}(x)$ which depend on all four spacetime coordinates (including the coordinate $x^{4}\in S^1$ of the compact dimension) and have vanishing components $A_{4}(x)$ (implying trivial holonomies in the 4-direction). Our calculation shows that the effective gauge-field action contains a local Chern-Simons-like term which violates Lorentz and CPT invariance. This result is established perturbatively with a generalized Pauli-Villars regularization and nonperturbatively with a lattice regularization based on Ginsparg-Wilson fermions., Comment: 48 pages, v7: published version

The existence of tiny neutrino masses at a scale more than a million times smaller than the lightest charged fermion mass, namely the electron, and their mixings can not be explained within the framework of the exceptionally successful Standard Model. There are four ideas that has been proposed to explain the tiny neutrino masses. These include the see-saw mechanism with a right handed neutrino at the GUT scale, and this is the most elegant mechanism. The other mechanisms are radiatively generated neutrino masses, the neutrino mass arising from a 2nd Higgs doublet having a tiny VEV and coupling only to the neutrinos, and finally the mirror model or simply the EW-scale $\nu_R$ model. The mirror model has new quarks and leptons of opposite chirality at the electroweak scale (for the same Standard Model gauge symmetry $SU(2)_W \times U(1)_Y$) compared to what we have for the Standard Model. With suitable modification of the Higgs sector, the EW-scale $\nu_R$ model satisfies the electroweak precision test and also the constraints coming from the observed 125-GeV Higgs scalar. Since in this model, the mirror fermions are required to be in the EW scale, these can be produced at the LHC giving final states with a very low background from the SM. One such final state is the same sign dileptons with large missing $p_T$ for the events. In this work, we explore the constraint provided by the $8$ TeV data, and prospect of observing this signal in the $13$ TeV runs at the LHC. Additional signals will be the presence of displaced vertices depending on the smallness of the Yukawa couplings of the mirror leptons with the ordinary leptons and the singlet Higgs present in the model. Of particular importance to the EW-scale $\nu_R$ model is the production of $\nu_R$ which will be a direct test of the seesaw mechanism at collider energies., Comment: 13 figures. arXiv admin note: text overlap with arXiv:1508.07318

Observation of non-zero neutrino masses at a scale $\sim 10^{-1} - 10^{-2}$ eV is a major problem in the otherwise highly successful Standard Model. The most elegant mechanism to explain such tiny neutrino masses is the seesaw mechanism with right handed neutrinos. However, the required seesaw scale is so high, $\sim 10^{14}$ GeV, it will not have any collider implications. Recently, an explicit model has been constructed to realize the seesaw mechanism with the right handed neutrinos at the electroweak scale. The model has a mirror symmetry having both the left and right lepton and quark doublets and singlets for the same $SU(2)_W $ gauge symmetry. Additional Higgs multiplets have been introduced to realize this scenario. It turns out that these extra Higgs fields also help to satisfy the precision electroweak tests, and other observables. Because the scale of the symmetry breaking is electroweak, both the mirror quark and mirror leptons have masses in the electroweak scale in the range $ \sim 150 - 800 $ GeV. The mirror quarks / leptons decay to ordinary quarks /leptons plus very light neutral scalars. In this work, we calculate the final state signals arising from the pair productions of these mirror quarks and their subsequent decays. We find that these signals are well observable over the Standard Model background for $13$ TeV LHC. Depending on the associated Yukawa couplings, these decays can also give rise displaced vertices with long decay length, very different from the usual displaced vertices associated with b decays., Comment: 31 pages, 10 figures, Typo corrected

The Berry phase for a variety of systems comprising of two angular momenta is discussed. These include the electron and proton in the ground state of the hydrogen atom (taking into account the hyperfine interaction), the positronium atom, the spin and orbital angular momenta of a single electron, muon capture by the deuteron in an external magnetic field, etc. Though the time scales involved, the underlying intrinsic Hamiltonians are quite different, as also the possible experimental probes, the geometric nature of the results for the Berry phase due to a time varying externally imposed magnetic field is found to be quite robust. Some indications are also put forward as to the possible interesting studies with time varying electric fields. The objective of this work is an attempt to broaden the scope of such studies in both the experimental and theoretical directions., Comment: 11 pages

This paper proposes a signal processing methodology of communication system and realized that circuits using operational transconductance amplifier (OTA). Two important classes of communication circuit, delta modulator and compander have been designed using that procedure. In the first implementation coded pulse modulation system is demonstrated which employ sampling, quantizing and coding to convert analog waveforms to digital signals while the second gives data compression and expansion in digital communication system. The proposed compander circuit is realized with operational transconductance amplifier and diode. Required power supply to operate the circuit is 3.5V. Performance of the circuits realized with OTAs has been demonstrated through SPICE simulation., Comment: Journal of Telecommunications,Volume 1, Issue 1, pp118-122, February 2010

We observed the nearby, low-density globular cluster M71 (NGC 6838) with the Chandra X-ray Observatory to study its faint X-ray populations. Five X-ray sources were found inside the cluster core radius, including the known eclipsing binary millisecond pulsar (MSP) PSR J1953+1846A. The X-ray light curve of the source coincident with this MSP shows marginal evidence for periodicity at the binary period of 4.2 h. Its hard X-ray spectrum and luminosity resemble those of other eclipsing binary MSPs in 47 Tuc, suggesting a similar shock origin of the X-ray emission. A further 24 X-ray sources were found within the half-mass radius, reaching to a limiting luminosity of 1.5 10^30 erg/s (0.3-8 keV). From a radial distribution analysis, we find that 18+/-6 of these 29 sources are associated with M71, somewhat more than predicted, and that 11+/-6 are background sources, both galactic and extragalactic. M71 appears to have more X-ray sources between L_X=10^30--10^31 erg/s than expected by extrapolating from other studied clusters using either mass or collision frequency. We explore the spectra and variability of these sources, and describe the results of ground-based optical counterpart searches., Comment: 36 pages including 7 figures and 8 tables, accepted by The Astrophysical Journal

Ethyl-hexyl substituted polyfluorene (PF) with its high level of molecular disorder can be described very well by one-carrier space-charge-limited conduction for a discrete set of trap levels with energy $\sim$ 0.5 eV above the valence band edge. Sweeping the bias above the trap-filling limit in the as-is polymer generates a new set of exponential traps, which is clearly seen in the density of states calculations. The trapped charges in the new set of traps have very long lifetimes and can be detrapped by photoexcitation. Thermal cycling the PF film to a crystalline phase prevents creation of additional traps at higher voltages., Comment: 13 pages, 4 figures. Physical Review B (accepted, 2007)

What happens to the entropy increase principle as the Universe evolve to form the big-crunch singularity? What happens to the uncertainity relations along the process of gravitational collapses? What is the quantum mechanical description of a Radon atom in a rigid box when the distance of consecutive nodes and antinodes of $\psi$ is equal to or less than the diameter of the atom? What is the position-space wave function of two finite volume massive bosons if we take contact interaction into account? How a photon produce electron-positron pair with finite volume concentrate rest masses? What are the charges of the electron-positron pairs forming loops in the vacuum? How two particles with three-momentums $k_1, k_2$ $(k_1 \neq k_2)$ produced to form a loop at a space-time point always arrive at another spacial point simultaneously? What is the microscopic explanation in terms of particle exchanges of the force in the Casimir effect? What is the mechanism of the collapse of the momentum-space wave function of a particle knocking out an elctron from an atom? What is meant by $|\Psi> = {c_1 (t)}|\Psi_{U^{238}}> + {c_2 (t)}|\Psi_{Th^{234}}> ~?$ Quantum mechanically the region between the rigid walls (which is equiprobable in classical mechanics) is non-homogeneous for a particle in a rigid box. A photon can not reproduce Maxwell's equations apart from moving with velocity $c$. How can a process involving only a few photons be described starting from the Maxwell's equations? The large scale structure of the Universe is homogeneous. What is the screen in our brains to view objects, as they are, of sizes larger than our brains?, Comment: This article is withdrawn due to some errors in Appendix:B and App.C. All the relevant discussions can be found in the references mentioned below: (1)INTERNATIONAL JOURNAL OF PURE AND APPLIED MATHEMATICS, Volume:76,No.2 (2012), pp.251. (2)INTERNATIONAL JOURNAL OF PURE AND APPLIED MATHEMATICS, Volume:76,No.2 (2012), pp.207. (3) arXIv:physics/0605061. (4) arXiv:0902.1601

What happens to the entropy increase principle as the Universe evolve to form the big-crunch singularity? What happens to the uncertainity relations along the process of gravitational collapses? What is the quantum mechanical description of a Radon atom in a rigid box when the distance of consecutive nodes and antinodes of $\psi$ is equal to or less than the diameter of the atom? What is the position-space wave function of two finite volume massive bosons if we take contact interaction into account? How a photon produce electron-positron pair with finite volume concentrate rest masses? What are the charges of the electron-positron pairs forming loops in the vacuum? How two particles with three-momentums $k_1, k_2$ $(k_1 \neq k_2)$ produced to form a loop at a space-time point always arrive at another spacial point simultaneously? What is the microscopic explanation in terms of particle exchanges of the force in the Casimir effect? What is the mechanism of the collapse of the momentum-space wave function of a particle knocking out an elctron from an atom? What is meant by $|\Psi> = {c_1 (t)}|\Psi_{U^{238}}> + {c_2 (t)}|\Psi_{Th^{234}}> ~?$ Quantum mechanically the region between the rigid walls (which is equiprobable in classical mechanics) is non-homogeneous for a particle in a rigid box ! The large scale structure of the Universe is homogeneous., Comment: This article is withdrawn due to some mistakes in Appendix.D The relevant discussions can be found in the following references: (1)INTERNATIONAL JOURNAL OF PURE AND APPLIED MATHEMATICS, Volume:76,No.2 (2012), pp.251. (2)INTERNATIONAL JOURNAL OF PURE AND APPLIED MATHEMATICS, Volume:76,No.2 (2012), pp.207. (3) arXiv:physics/0605061. (4) arXiv:0902.1601

We present the results of Raman and photoluminescence (PL) studies on epitaxial anatase phase Ti$_{1-x}$Co$_x$O$_2$ films for $x$ = 0-0.07, grown by pulsed laser deposition. The low doped system ($x$=0.01 and 0.02) shows a Curie temperature of ~700 K in the as-grown state. The Raman spectra from the doped and undoped films confirm their anatase phase. The photoluminescence spectrum is characterized by a broad emission from self-trapped excitons (STE) at 2.3 eV at temperatures below 120 K. This peak is characteristic of the anatase-phase TiO$_2$ and shows a small blueshift with increasing doping concentration. In addition to the emission from STE, the Co-doped samples show two emission lines at 2.77 eV and 2.94 eV that are absent in the undoped film indicative of a spin-flip energy., Comment: 8 pages, 4 figures

The X-ray sources observed in nearby galaxies show brightness distributions (log(N(>S))--log(S) curves) which can be described as single or broken power laws. Single power-law distributions are often found for sources in galaxies with vigorous ongoing star-formation activity, while broken power laws are found in elliptical galaxies and in bulges of spiral galaxies. The luminosity break can be caused by a population of X-ray binaries which contain a neutron star accreting at the Eddington limit or by aging of the X-ray binary population. We show that a simple birth-death model can reproduce single and broken power-law log(N(>S))--log(S) curves. We have found that power-law log(N(>S))--log(S) curves are a consequence of smooth continuous formation of X-ray binaries and a luminosity break is the signature of a starburst episode in the recent past. The luminosity break is robust and is determined by the lifespans of the X-ray binaries relative to the look-back time to the starburst epoch. The model successfully explains the different forms of log(N(>S))--log(S) curves for the disk and bulge sources in the spiral galaxy M81., Comment: 4 pages, to appear in ``New Visions of the X-ray Universe in the XMM-Newton and Chandra Era''

We consider the thermodynamics of minimally coupled massive scalar field in 3+1 dimensional constant curvature black hole background. The brick wall model of 't Hooft is used. When Schwarzschild like coordinates are used it is found that two radial brick wall cut-off parameters are required to regularize the solution. Free energy of the scalar field is obtained through counting of states using the WKB approximation. It is found that the free energy and the entropy are divergent in both the cut-off parameters., Comment: Latex,15 pages; a few discussions added, a new reference added

In this article we discuss a few aspects of the space-time description of fields and particles. In sectionn II and III we demonstrate that fields are as fundamental as particles. In section IV we discuss non-equivalence of the Schwarzschild coordinates and the Kruskal-Szekeres coordinates. In section V we discuss that it is not possible to define causal structure in discrete space-time manifolds. In App.B we show that a line is not just a collection of points and we will have to introduce one-dimensional line-intervals as fundamental geometric elements. Similar discussions are valid for area and volume-elements. In App.C and App.D we make a comparative study of Quantum Field Theory and Quantum Mechanics and contradictions associated with probabilistics interpretation of these theories with space-time dimensional analysis. In App.E and App.F we discuss the geometry of Robertson-Walker model and electrostatic behavior of dielectrics respectively. In Sup.I we discuss the regularity of Spin-Spherical harmonics and also derive an energy-spectrum which is free of back-reaction problem. In Sup.II we discuss that in general the integral version of Gauss's divergence law in Electrodynamics is not valid and rederive Gauss's law and Ampere's law. We also show that under duality transformation magnetic charge conservation law do not remain time reversal symmetric. In Sup.III we derive the complete equation for viscous compressible fluids and make a few comments regarding some cotradictions associated with boundary conditions for fluid dynamics. In Sup.IV we discuss a few aspects on double slit interference experiments. We conclude this article with a few questions in Sup.V., Comment: Revtex, 26 pages, A few sections are added