Abstract: We study a spherically symmetric setup consisting of a Schwarzschild metric as the background geometry in the framework of classical polymerization. This process is an extension of the polymeric representation of quantum mechanics in such a way that a transformation maps classical variables to their polymeric counterpart. We show that the usual Schwarzschild metric can be extracted from a Hamiltonian function which in turn gets modifications due to the classical polymerization. Then, the polymer corrected Schwarzschild metric may be obtained by solving the polymer-Hamiltonian equations of motion. It is shown that while the conventional Schwarzschild space-time is a vacuum solution of the Einstein equations, its polymer-corrected version corresponds to an energy-momentum tensor that exhibits the features of dark energy. We also use the resulting metric to investigate some thermodynamical quantities associated with the Schwarzschild black hole, and in comparison with the standard Schwarzschild metric the similarities and differences are discussed. PubDate: Thu, 20 Sep 2018 00:00:00 +000
Abstract: The behaviour of massive and massless test particles around asymptotically flat and spherically symmetric, charged black holes in the context of generalized dilaton-axion gravity in four dimensions is studied. All the possible motions are investigated by calculating and plotting the corresponding effective potential for the massless and massive particles as well. Further, the motion of massive (charged or uncharged) test particles in the gravitational field of charged black holes in generalized dilaton-axion gravity for the cases of static and nonstatic equilibrium is investigated by applying the Hamilton-Jacobi approach. PubDate: Sun, 16 Sep 2018 06:44:07 +000
Abstract: The scintillating properties of active materials used in high energy and particle physics experiments play an important role regarding the performances of both calorimeters and experiments. Two scintillator materials, a scintillating glass and an inorganic crystals, were examined to be used for collider experiments showing good optical and scintillating properties. This paper discusses the simulated performances of two materials of interest assembled in a scintillator-photodetector combination. The computational study was carried out with Geant4 simulation program to determine energy resolutions of such calorimeter with different beam energies and calorimeter sizes. PubDate: Thu, 13 Sep 2018 00:00:00 +000
Abstract: We propose an alternative description of the Schwarzschild black hole based on the requirement that the solution is static not only outside the horizon but also inside it. As a consequence of this assumption, we are led to a change of signature implying a complex transformation of an angle variable. There is a “phase transition” on the surface , producing a change in the symmetry as we cross this surface. Some consequences of this situation on the motion of test particles are investigated. PubDate: Wed, 12 Sep 2018 06:35:10 +000
Abstract: We study the approximate scattering state solutions of the Duffin-Kemmer-Petiau equation (DKPE) and the spinless Salpeter equation (SSE) with the Hellmann potential. The eigensolutions, scattering phase shifts, partial-waves transitions, and the total cross section for all the partial waves are obtained and discussed. The dependence of partial-waves transitions on total angular momentum number, angular momentum number, mass combination, and potential parameters was presented in the figures. PubDate: Sun, 09 Sep 2018 08:16:12 +000
Abstract: We investigate the implications of a sterile neutrino on the physics potential of the proposed experiment DUNE and future runs of NOA using latest NOA results. Using combined analysis of the disappearance and appearance data, NOA reported preferred solutions at normal hierarchy (NH) with two degenerate best-fit points: one in the lower octant (LO) and = 1.48 and the other in higher octant (HO) and = 0.74. Another solution of inverted hierarchy (IH), which is 0.46 away from best fit, was also reported. We discuss chances of resolving these degeneracies in the presence of sterile neutrino. PubDate: Thu, 06 Sep 2018 06:53:22 +000
Abstract: In this work, we study the quantum system with the symmetric Razavy potential and show how to find its exact solutions. We find that the solutions are given by the confluent Heun functions. The eigenvalues have to be calculated numerically. The properties of the wave functions depending on are illustrated graphically for a given potential parameter . We find that the even and odd wave functions with definite parity are changed to odd and even wave functions when the potential parameter increases. This arises from the fact that the parity, which is a defined symmetry for very small , is completely violated for large . We also notice that the energy levels decrease with the increasing potential parameter . PubDate: Tue, 28 Aug 2018 08:58:56 +000
Abstract: Event detection rates for WIMP-nucleus interactions are calculated for Ga, Ge, As, and I (direct dark matter detectors). The nuclear structure form factors, which are rather independent of the underlying beyond the Standard Model particle physics scenario assumed, are evaluated within the context of the deformed nuclear shell model (DSM) based on Hartree-Fock nuclear states. Along with the previously published DSM results for Ge, the neutrino-floor due to coherent elastic neutrino-nucleus scattering (CENS), an important source of background to dark matter searches, is extensively calculated. The impact of new contributions to CENS due to neutrino magnetic moments and mediators at direct dark matter detection experiments is also examined and discussed. The results show that the neutrino-floor constitutes a crucial source of background events for multi-ton scale detectors with sub-keV capabilities. PubDate: Sun, 26 Aug 2018 06:51:26 +000
Abstract: We consider a cosmology with decaying metastable dark energy and assume that a decay process of this metastable dark energy is a quantum decay process. Such an assumption implies among others that the evolution of the Universe is irreversible and violates the time reversal symmetry. We show that if we replace the cosmological time appearing in the equation describing the evolution of the Universe by the Hubble cosmological scale time, then we obtain time dependent in the form of the series of even powers of the Hubble parameter :. Our special attention is focused on radioactive-like exponential form of the decay process of the dark energy and on the consequences of this type decay. PubDate: Sun, 19 Aug 2018 08:11:23 +000
Abstract: We propose a general expression for the probability distribution of real-valued tunneling times of a localized particle, as measured by the Salecker-Wigner-Peres quantum clock. This general expression is used to obtain the distribution of times for the scattering of a particle through a static rectangular barrier and for the tunneling decay of an initially bound state after the sudden deformation of the potential, the latter case being relevant to understand tunneling times in recent attosecond experiments involving strong field ionization. PubDate: Sun, 19 Aug 2018 06:59:49 +000
Abstract: Decaying vacuum cosmological models evolving smoothly between two extreme (very early and late time) de Sitter phases are able to solve or at least to alleviate some cosmological puzzles; among them we have (i) the singularity, (ii) horizon, (iii) graceful-exit from inflation, and (iv) the baryogenesis problem. Our basic aim here is to discuss how the coincidence problem based on a large class of running vacuum cosmologies evolving from de Sitter to de Sitter can also be mollified. It is also argued that even the cosmological constant problem becomes less severe provided that the characteristic scales of the two limiting de Sitter manifolds are predicted from first principles. PubDate: Thu, 16 Aug 2018 00:00:00 +000
Abstract: We study nonlinear cosmological perturbations and their possible non-Gaussian character in an extended nonminimal inflation where gravity is coupled nonminimally to both the scalar field and its derivatives. By expansion of the action up to the third order, we focus on the nonlinearity and non-Gaussianity of perturbations in comparison with recent observational data. By adopting an inflation potential of the form , we show that, for , for instance, this extended model is consistent with observation if in appropriate units. By restricting the equilateral amplitude of non-Gaussianity to the observationally viable values, the coupling parameter is constrained to the values . PubDate: Wed, 15 Aug 2018 00:00:00 +000
Abstract: The dual magnetohydrodynamics of dyonic plasma describes the study of electrodynamics equations along with the transport equations in the presence of electrons and magnetic monopoles. In this paper, we formulate the quaternionic dual fields equations, namely, the hydroelectric and hydromagnetic fields equations which are an analogous to the generalized Lamb vector field and vorticity field equations of dyonic cold plasma fluid. Further, we derive the quaternionic Dirac-Maxwell equations for dual magnetohydrodynamics of dyonic cold plasma. We also obtain the quaternionic dual continuity equations that describe the transport of dyonic fluid. Finally, we establish an analogy of Alfven wave equation which may generate from the flow of magnetic monopoles in the dyonic field of cold plasma. The present quaternionic formulation for dyonic cold plasma is well invariant under the duality, Lorentz, and CPT transformations. PubDate: Tue, 14 Aug 2018 06:07:43 +000
Abstract: We probe the shock wave geometry with the mutual correlation in a spherically symmetric Reissner-Nordström AdS black hole on the basis of the gauge/gravity duality. In the static background, we find that the regions living on the boundary of the AdS black holes are correlated provided the considered regions on the boundary are large enough. We also investigate the effect of the charge on the mutual correlation and find that the bigger the value of the charge is, the smaller the value of the mutual correlation will be. As a small perturbation is added at the AdS boundary, the horizon shifts and a dynamical shock wave geometry form after long time enough. In this dynamic background, we find that the greater the shift of the horizon is, the smaller the mutual correlation will be. Especially for the case that the shift is large enough, the mutual correlation vanishes, which implies that the considered regions on the boundary are uncorrelated. The effect of the charge on the mutual correlation in this dynamic background is found to be the same as that in the static background. PubDate: Mon, 13 Aug 2018 09:34:09 +000
Abstract: Accepting the Komar mass definition of a source with energy-momentum tensor and using the thermodynamic pressure definition, we find a relaxed energy-momentum conservation law. Thereinafter, we study some cosmological consequences of the obtained energy-momentum conservation law. It has been found out that the dark sectors of cosmos are unifiable into one cosmic fluid in our setup. While this cosmic fluid impels the universe to enter an accelerated expansion phase, it may even show a baryonic behavior by itself during the cosmos evolution. Indeed, in this manner, while behaves baryonically, a part of it, namely, which is satisfying the ordinary energy-momentum conservation law, is responsible for the current accelerated expansion. PubDate: Thu, 09 Aug 2018 08:15:03 +000
Abstract: We present another example of superfluid black hole containing phase transition in Horava gravity. After studying the extended thermodynamics of general dimensional Horava-Lifshitz AdS black holes, it is found that only the one with spherical horizon in four and five dimensions has phase transition, which is a line of (continuous) second-order phase transitions and was famous in the discussion of superfluidity of liquid . The “superfluid” black hole phase and “normal” black hole phase are also distinguished. Particularly, six-dimensional Horava-Lifshitz AdS black holes exhibit infinitely many critical points in plane and the divergent points for specific heat, for which they only contain the “normal” black hole phase and the “superfluid” black hole phase disappears due to the physical temperature constraint; therefore there is no similar phase transition. In more than six dimensions, there is no critical behavior. After choosing the appropriate ordering field, we study the critical phenomena in different planes of thermodynamical phase space. We also calculate the critical exponents, which are the same as the van der Waals fluid. PubDate: Thu, 09 Aug 2018 08:05:55 +000
Abstract: We present cross-section predictions for the isolated diphoton production in next-to-next-to-leading order (NNLO) QCD using the computational framework MATRIX. Both the integrated and the differential fiducial cross-sections are calculated. We found that the arbitrary setup of the isolation procedure introduces uncertainties with a size comparable to the estimation of the theoretical uncertainties obtained with the customary variation of the factorization and renormalization scales. This fact is taken into account in the final result. PubDate: Tue, 07 Aug 2018 07:43:28 +000
Abstract: We use the scalar field constructed in phase space to analyze the analogous Stefan-Boltzmann law and Casimir effect, both of them at finite temperature. The temperature is introduced by Thermo Field Dynamics (TFD) formalism and the quantities are analyzed once projected in the space of coordinates. We show that using the framework of phase space it is possible to introduce a thermal energy which is related to temperature as it vanishes when the temperature tends to zero. In fact given such a correlation the formalism of TFD is equivalent when project is in momenta space when compared to coordinates space. PubDate: Tue, 07 Aug 2018 00:00:00 +000
Abstract: Nonsupersymmetric minimal SU(5) with Higgs representations and and standard fermions in is well known for its failure in unification of gauge couplings and lack of predicting neutrino masses. Like standard model, it is also affected by the instability of the Higgs scalar potential. We note that extending the Higgs sector by and not only leads to the popular type-II seesaw ansatz for neutrino masses with a lower bound on the triplet mass GeV, but also achieves precision unification of gauge couplings without proliferation of nonstandard light Higgs scalars or fermions near the TeV scale. Consistent with recent LUX-2016 lower bound, the model easily accommodates a singlet scalar WIMP dark matter near the TeV scale which resolves the vacuum stability issue even after inclusion of heavy triplet threshold effect. We estimate proton lifetime predictions for including uncertainties due to input parameters and threshold effects due to superheavy Higgs scalars and superheavy gauge bosons. The predicted lifetime is noted to be verifiable at Super Kamiokande and Hyper Kamiokande experiments. PubDate: Mon, 06 Aug 2018 00:00:00 +000
Abstract: A hypothetical scalar mixed with the standard model Higgs appears in few contexts of new physics. This study addresses the question what mass range is in the reach of TeV LHC given different magnitudes of mixing angle , where event simulations are based on production from vector-boson fusion channel and decays into SM leptons through or . It indicates that heavy scalar mass up to GeV and GeV can be excluded by integrated luminosity of 300 and 3000 , respectively, for larger than . PubDate: Thu, 02 Aug 2018 06:31:19 +000
Abstract: We reassess the subject of topological gravity by following the shift supersymmetry formalism. The gauge-fixing of the theory goes under the Batalin-Vilkovisky (BV) prescription based on a diagram that contains both ghost and antighost superfields, associated with the supervielbein and the super-Lorentz connection. We extend the formulation of the topological gravity action to an arbitrary number of dimensions of the shift superspace by adopting a formulation based on the gauge-fixing for BF-type models. PubDate: Wed, 01 Aug 2018 00:00:00 +000
Abstract: We have studied phenomenological implication of R-parity violating () Minimal Supersymmetric Model (MSSM) via analyses of pure leptonic () and semileptonic decays of pseudoscalar mesons (). These analyses involve comparison between theoretical predictions made by MSSM and the Standard Model (SM) with the experimental results like branching fractions of the said process. We have found, in general, that contribution dominates over the SM contribution, i.e., by a factor of for the pure leptonic decays of and by and in case of and , respectively. Furthermore, the limits obtained on Yukawa couplings by using are used to calculate This demonstrates the role of MSSM as a viable model for the study of new physics contribution in rare decays at places like Super B factories, KOTO (J-PARC) and NA62 at CERN. PubDate: Wed, 01 Aug 2018 00:00:00 +000
Abstract: Since the doubly heavy baryons masses are experimentally unknown (except and ), we present the ground state masses and the positive and negative parity excited state masses of doubly heavy baryons. For this purpose, we have solved the six-dimensional hyperradial Schrödinger equation analytically for three particles under the hypercentral potential by using the ansatz approach. In this paper, the hypercentral potential is regarded as a combination of the color Coulomb plus linear confining term and the six-dimensional harmonic oscillator potential. We also added the first-order correction and the spin-dependent part contains three types of interaction terms (the spin-spin term, spin-orbit term, and tensor term) to the hypercentral potential. Our obtained masses for the radial excited states and orbital excited states of ,,,,, and systems are compared with other theoretical reports, which could be a beneficial tool for the interpretation of experimentally unknown doubly heavy baryons spectrum. PubDate: Thu, 26 Jul 2018 00:00:00 +000
Abstract: This paper is devoted to study the cosmological behavior of homogeneous and isotropic universe model in the context of gravity, where is the scalar field. For this purpose, we follow the first-order formalism defined by . We evaluate Hubble parameter, effective equation of state parameter , deceleration parameter, and potential of scalar field for three different values of . We obtain phantom era in some cases for the early times. It is found that exponential expression of yields independent of time for flat universe and independent of model parameter otherwise. It is concluded that our model corresponds to CDM for both initial and late times. PubDate: Thu, 26 Jul 2018 00:00:00 +000
Abstract: Most of the theoretical physics known today is described by using a small number of differential equations. For linear systems, different forms of the hypergeometric or the confluent hypergeometric equations often suffice to describe the system studied. These equations have power series solutions with simple relations between consecutive coefficients and/or can be represented in terms of simple integral transforms. If the problem is nonlinear, one often uses one form of the Painlevé equations. There are important examples, however, where one has to use higher order equations. Heun equation is one of these examples, which recently is often encountered in problems in general relativity and astrophysics. Its special and confluent forms take names as Mathieu, Lamé, and Coulomb spheroidal equations. For these equations whenever a power series solution is written, instead of a two-way recursion relation between the coefficients in the series, we find one between three or four different ones. An integral transform solution using simpler functions also is not obtainable. The use of this equation in physics and mathematical literature exploded in the later years, more than doubling the number of papers with these solutions in the last decade, compared to time period since this equation was introduced in 1889 up to 2008. We use SCI data to conclude this statement, which is not precise, but in the correct ballpark. Here this equation will be introduced and examples for its use, especially in general relativity literature, will be given. PubDate: Thu, 19 Jul 2018 07:12:31 +000
Abstract: The importance of the energy spectrum of bound states and their restrictions in quantum mechanics due to the different methods have been used for calculating and determining the limit of them. Comparison of Schrödinger-like equation obtained by Dirac equation with the nonrelativistic solvable models is the most efficient method. By this technique, the exact relativistic solutions of Dirac equation for Hartmann and Ring-Shaped Oscillator Potentials are accessible, when the scalar potential is equal to the vector potential. Using solvable nonrelativistic quantum mechanics systems as a basic model and considering the physical conditions provide the changes in the restrictions of relativistic parameters based on the nonrelativistic definitions of parameters. PubDate: Wed, 18 Jul 2018 00:00:00 +000
Abstract: Using the semiclassical WKB approximation and Hamilton-Jacobi method, we solve an equation of motion for the Glashow-Weinberg-Salam model, which is important for understanding the unified gauge-theory of weak and electromagnetic interactions. We calculate the tunneling rate of the massive charged W-bosons in a background of electromagnetic field to investigate the Hawking temperature of black holes surrounded by perfect fluid in Rastall theory. Then, we study the quantum gravity effects on the generalized Proca equation with generalized uncertainty principle (GUP) on this background. We show that quantum gravity effects leave the remnants on the Hawking temperature and the Hawking radiation becomes nonthermal. PubDate: Wed, 18 Jul 2018 00:00:00 +000
Abstract: We studied the thermodynamics and spectroscopy of a -dimensional, Lifshitz black hole (LBH). Using Wald’s entropy formula and the Hawking temperature, we derived the quasi-local mass of the LBH. Based on the exact solution to the near-horizon Schrödinger-like equation (SLE) of the massive scalar waves, we computed the quasi-normal modes of the LBH via employing the adiabatic invariant quantity for the LBH. This study shows that the entropy and area spectra of the LBH are equally spaced. PubDate: Tue, 17 Jul 2018 00:00:00 +000
Abstract: Two-particle Hanbury-Brown-Twiss (HBT) interferometry is an important probe for understanding the space-time structure of particle emission sources in high energy heavy ion collisions. We present the comparative studies of HBT radii in Pb+Pb collisions at = 17.3 GeV with Au+Au collisions at = 19.6 GeV. To further understand this specific energy regime, we also compare the HBT radii for Au+Au collisions at = 19.6 GeV with Cu+Cu collisions at = 22.4 GeV. We have found interesting similarity in the ratio with across the collision systems while comparing the data for this specific energy zone which is interesting as it acts as a bridge from SPS energy regime to the RHIC energy domain. PubDate: Sun, 15 Jul 2018 08:15:19 +000
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