Advances in High Energy Physics
[SJR: 1.297] [H-I: 7] [14 followers] Follow
Open Access journal
ISSN (Print) 1687-7357 - ISSN (Online) 1687-7365
Published by Hindawi Publishing Corporation [372 journals]
- Phase Transition of the Higher Dimensional Charged Gauss-Bonnet Black Hole
in de Sitter Spacetime
Abstract: We study the phase transition of charged Gauss-Bonnet-de Sitter (GB-dS) black hole. For black holes in de Sitter spacetime, there is not only black hole horizon, but also cosmological horizon. The thermodynamic quantities on both horizons satisfy the first law of the black hole thermodynamics, respectively; moreover, there are additional connections between them. Using the effective temperature approach, we obtained the effective thermodynamic quantities of charged GB-dS black hole. According to Ehrenfest classification, we calculate some response functions and plot their figures, from which one can see that the spacetime undergoes a second-order phase transition at the critical point. It is shown that the critical values of effective temperature and pressure decrease with the increase of the value of GB parameter .
PubDate: Sun, 01 Mar 2015 12:23:51 +000
- Weak Minimal Area in Entanglement Entropy
Abstract: We revisit the minimal area condition of Ryu-Takayanagi in the holographic calculation of the entanglement entropy, in particular, the Legendre test and the Jacobi test. The necessary condition for the weak minimality is checked via Legendre test and its sufficient nature via Jacobi test. We show for AdS black hole with a strip type entangling region that it is this minimality condition that makes the hypersurface unable to cross the horizon, which is in agreement with that studied earlier by Engelhardt et al. and Hubeny using a different approach. Moreover, demanding the weak minimality condition on the entanglement entropy functional with the higher derivative term puts a constraint on the Gauss-Bonnet coupling; that is, there should be an upper bound on the value of the coupling, .
PubDate: Thu, 26 Feb 2015 11:22:35 +000
- Theoretical and Phenomenological Status of Neutrino Physics: A Brief
Abstract: We present an overview of recent progress in the theoretical and phenomenological studies of neutrino masses, lepton avor mixing, and CP violation. Firstly, We discuss the status of neutrino mass with in the Standard Model (SM) of particle physics. Then the possible ways in which neutrino mass terms can be included in the SM are discussed. The inclusion of new physics beyond the SM inevitably brings new parameters which are not constrained by the present experimental data on neutrino masses and mixing angles and, thus, are free parameters of the theory. We, also, discuss various theoretically motivated phenomenological approaches which can be used to reduce the number of free parameters and, thus, provide an excellent tool to understand the underlying physics of neutrino masses and mixings. Current experimental constraints on the neutrino mass spectrum and the lepton avor mixing parameters, including the recent observation of nonzero , have been summarized. Finally, We discuss the renewed interest in the possible existence of one or more sterile neutrinos and their phenomenology.
PubDate: Wed, 25 Feb 2015 07:36:04 +000
- An Alternative Approach to Solutions of the MGECSC Potential in Presence
of External Electric Field
Abstract: For the first time the Schrödinger equation with more general exponential cosine screened Coulomb potential in the presence of external electric field is solved approximately and analytically by applying an ansatz to eigenfunction of corresponding Hamiltonian and then energy values and wave functions are obtained. Since this potential turns into four different potential cases when considering different cases of the parameters in the potential, energies and eigenfunctions for these four different potentials are already to be found by solving Schrödinger equation with MGECSC potential. Energy values and wave functions obtained by using different values of potential parameters for each of these four different potential are compared with the results of other studies. Since the obtained general solutions in this study have been found in the presence of external electric field, the external electric field effects on systems with the mentioned four different potentials are also easily investigated. One of advantages of the present results and method is that if external electric field is equal to zero, general mathematical structure of corresponding equations does not change and then electric field effect can be eliminated. The presence or absence of electric field does not prevent solving the Schrödinger equation analytically.
PubDate: Mon, 23 Feb 2015 07:26:54 +000
- Holographic Fermions in Anisotropic Einstein-Maxwell-Dilaton-Axion Theory
Abstract: We investigate the properties of the holographic Fermionic system dual to an anisotropic charged black brane bulk in Einstein-Maxwell-Dilaton-Axion gravity theory. We consider the minimal coupling between the Dirac field and the gauge field in the bulk gravity theory and mainly explore the dispersion relation exponents of the Green functions of the dual Fermionic operators in the dual field theory. We find that along both the anisotropic and the isotropic directions the Fermi momentum will be effected by the anisotropy of the bulk theory. However, the anisotropy has influence on the dispersion relation which is almost linear for massless Fermions with charge . The universal properties that the mass and the charge of the Fermi possibly correspond to nonlinear dispersion relation are also investigated.
PubDate: Sun, 22 Feb 2015 12:03:27 +000
- Evaluation of the Cosmological Constant in Inflation with a Massive
Nonminimal Scalar Field
Abstract: In Schrödinger picture we study the possible effects of trans-Planckian physics on the quantum evolution of massive nonminimally coupled scalar field in de Sitter space. For the nonlinear Corley-Jacobson type dispersion relations with quartic or sextic correction, we obtain the time evolution of the vacuum state wave functional during slow-roll inflation and calculate explicitly the corresponding expectation value of vacuum energy density. We find that the vacuum energy density is finite. For the usual dispersion parameter choice, the vacuum energy density for quartic correction to the dispersion relation is larger than for sextic correction, while for some other parameter choices, the vacuum energy density for quartic correction is smaller than for sextic correction. We also use the backreaction to constrain the magnitude of parameters in nonlinear dispersion relation and show how the cosmological constant depends on the parameters and the energy scale during the inflation at the grand unification phase transition.
PubDate: Sun, 15 Feb 2015 08:45:28 +000
- Dynamics of Generalized Tachyon Field in Teleparallel Gravity
Abstract: We study dynamics of generalized tachyon scalar field in the framework of teleparallel gravity. This model is an extension of tachyonic teleparallel dark energy model which has been proposed by Banijamali and Fazlpour (2012). In contrast with tachyonic teleparallel dark energy model that has no scaling attractors, here we find some scaling attractors which means that the cosmological coincidence problem can be alleviated. Scaling attractors are presented for both interacting and noninteracting dark energy and dark matter cases.
PubDate: Thu, 12 Feb 2015 12:59:51 +000
- More about the Mass of the New Charmonium States
Abstract: If is described by the picture as a mixture of the charmonium and molecular states; as a mixture of the and states; and as a mixture of the tetraquark and charmonium states, their orthogonal combinations should also exist. We estimate the mass and residues of the states within the QCD sum rules method. We find that the mass splitting among and their orthogonal states is at most 200 MeV. Experimental search of these new states can play critical role for establishing the nature of the new charmonium states.
PubDate: Wed, 11 Feb 2015 09:38:31 +000
- Resonance Spectra of Caged Stringy Black Hole and Its Spectroscopy
Abstract: Maggiore’s method (MM), which evaluates the transition frequency that appears in the adiabatic invariant from the highly damped quasinormal mode (QNM) frequencies, is used to investigate the entropy/area spectra of the Garfinkle–Horowitz–Strominger black hole (GHSBH). Instead of the ordinary QNMs, we compute the boxed QNMs (BQNMs) that are the characteristic resonance spectra of the confined scalar fields in the GHSBH geometry. For this purpose, we assume that the GHSBH has a confining cavity (mirror) placed in the vicinity of the event horizon. We then show how the complex resonant frequencies of the caged GHSBH are computed using the Bessel differential equation that arises when the scalar perturbations around the event horizon are considered. Although the entropy/area is characterized by the GHSBH parameters, their quantization is shown to be independent of those parameters. However, both spectra are equally spaced.
PubDate: Mon, 09 Feb 2015 14:23:43 +000
- Rare Decay in Family Nonuniversal Model
Abstract: The rare decay with polarized photon is studied in the framework of a family nonuniversal model. The branching ratio and photon polarization asymmetry to the model parameters are calculated and compared with the Standard Model. Deviations from the Standard Model will indicate the presence of new physics.
PubDate: Tue, 03 Feb 2015 06:27:33 +000
- Regular Bulk Solutions in Brane-Worlds with Inhomogeneous Dust and
Generalized Dark Radiation
Abstract: From the dynamics of a brane-world with matter fields present in the bulk, the bulk metric and the black string solution near the brane are generalized, when both the dynamics of inhomogeneous dust/generalized dark radiation on the brane-world and inhomogeneous dark radiation in the bulk as well are considered as exact dynamical collapse solutions. Based on the analysis on the inhomogeneous static exterior of a collapsing sphere of homogeneous dark radiation on the brane, the associated black string warped horizon is studied, as well as the 5D bulk metric near the brane. Moreover, the black string and the bulk are shown to be more regular upon time evolution, for suitable values for the dark radiation parameter in the model, by analyzing the soft physical singularities.
PubDate: Thu, 29 Jan 2015 17:23:48 +000
- Through Neutrino Eyes: The Search for New Physics
PubDate: Thu, 29 Jan 2015 13:48:24 +000
- Searching for Neutrinoless Double-Beta Decay of 130Te with CUORE
Abstract: Neutrinoless double-beta (0) decay is a hypothesized lepton-number-violating process that offers the only known means of asserting the possible Majorana nature of neutrino mass. The Cryogenic Underground Observatory for Rare Events (CUORE) is an upcoming experiment designed to search for 0 decay of 130Te using an array of 988 TeO2 crystal bolometers operated at 10 mK. The detector will contain 206 kg of 130Te and have an average energy resolution of 5 keV; the projected 0 decay half-life sensitivity after five years of livetime is 1.6 × 1026 y at 1 (9.5 × 1025 y at the 90% confidence level), which corresponds to an upper limit on the effective Majorana mass in the range 40–100 meV (50–130 meV). In this paper, we review the experimental techniques used in CUORE as well as its current status and anticipated physics reach.
PubDate: Wed, 28 Jan 2015 12:41:15 +000
- Beyond Standard Model Searches in the MiniBooNE Experiment
Abstract: The MiniBooNE experiment has contributed substantially to beyond standard model searches in the neutrino sector. The experiment was originally designed to test the eV2 region of the sterile neutrino hypothesis by observing () charged current quasielastic signals from a () beam. MiniBooNE observed excesses of and candidate events in neutrino and antineutrino mode, respectively. To date, these excesses have not been explained within the neutrino standard model (SM); the standard model extended for three massive neutrinos. Confirmation is required by future experiments such as MicroBooNE. MiniBooNE also provided an opportunity for precision studies of Lorentz violation. The results set strict limits for the first time on several parameters of the standard-model extension, the generic formalism for considering Lorentz violation. Most recently, an extension to MiniBooNE running, with a beam tuned in beam-dump mode, is being performed to search for dark sector particles. This review describes these studies, demonstrating that short baseline neutrino experiments are rich environments in new physics searches.
PubDate: Wed, 28 Jan 2015 08:15:08 +000
- Regularization of Gravity Theories and Local Lorentz Transformation
Abstract: We regularized the field equations of gravity theories such that the effect of local Lorentz transformation (LLT), in the case of spherical symmetry, is removed. A “general tetrad field,” with an arbitrary function of radial coordinate preserving spherical symmetry, is provided. We split that tetrad field into two matrices; the first represents a LLT, which contains an arbitrary function, and the second matrix represents a proper tetrad field which is a solution to the field equations of gravitational theory (which are not invariant under LLT). This “general tetrad field” is then applied to the regularized field equations of . We show that the effect of the arbitrary function which is involved in the LLT invariably disappears.
PubDate: Mon, 26 Jan 2015 09:49:24 +000
- Minimal Length Effects on Tunnelling from Spherically Symmetric Black
Abstract: We investigate effects of the minimal length on quantum tunnelling from spherically symmetric black holes using the Hamilton-Jacobi method incorporating the minimal length. We first derive the deformed Hamilton-Jacobi equations for scalars and fermions, both of which have the same expressions. The minimal length correction to the Hawking temperature is found to depend on the black hole’s mass and the mass and angular momentum of emitted particles. Finally, we calculate a Schwarzschild black hole's luminosity and find the black hole evaporates to zero mass in infinite time.
PubDate: Thu, 22 Jan 2015 14:24:49 +000
- Direct Dark Matter Search
PubDate: Thu, 22 Jan 2015 11:46:56 +000
- Scalar Form Factor of the Pion in the Kroll-Lee-Zumino Field Theory
Abstract: The renormalizable Kroll-Lee-Zumino field theory of pions and a neutral rho-meson is used to determine the scalar form factor of the pion in the space-like region at next-to-leading order. Perturbative calculations in this framework are parameter-free, as the masses and the rho-pion-pion coupling are known from experiment. Results compare favorably with lattice QCD calculations.
PubDate: Wed, 21 Jan 2015 12:54:48 +000
- Retracted: Performance of Water-Based Liquid Scintillator: An Independent
PubDate: Tue, 20 Jan 2015 11:09:13 +000
- The DarkSide Multiton Detector for the Direct Dark Matter Search
Abstract: Although the existence of dark matter is supported by many evidences, based on astrophysical measurements, its nature is still completely unknown. One major candidate is represented by weakly interacting massive particles (WIMPs), which could in principle be detected through their collisions with ordinary nuclei in a sensitive target, producing observable low-energy (<100 keV) nuclear recoils. The DarkSide program aims at the WIPMs detection using a liquid argon time projection chamber (LAr-TPC). In this paper we quickly review the DarkSide program focusing in particular on the next generation experiment DarkSide-G2, a 3.6-ton LAr-TPC. The different detector components are described as well as the improvements needed to scale the detector from DarkSide-50 (50 kg LAr-TPC) up to DarkSide-G2. Finally, the preliminary results on background suppression and expected sensitivity are presented.
PubDate: Tue, 20 Jan 2015 09:20:42 +000
- Weyl-Invariant Extension of the Metric-Affine Gravity
Abstract: Metric-affine geometry provides a nontrivial extension of the general relativity where the metric and connection are treated as the two independent fundamental quantities in constructing the spacetime (with nonvanishing torsion and nonmetricity). In this paper, we study the generic form of action in this formalism and then construct the Weyl-invariant version of this theory. It is shown that, in Weitzenböck space, the obtained Weyl-invariant action can cover the conformally invariant teleparallel action. Finally, the related field equations are obtained in the general case.
PubDate: Tue, 20 Jan 2015 06:23:32 +000
- A Study of Universal Thermodynamics in Brane World Scenario
Abstract: A study of Universal thermodynamics is done in the framework of RSII brane model and DGP brane scenario. The Universe is chosen as FRW model bounded by apparent or event horizon. Assuming extended Hawking temperature on the horizon, the unified first law is examined for perfect fluid (with constant equation of state) and Modified Chaplygin Gas model. As a result there is a modification of Bekenstein entropy on the horizons. Further the validity of the generalized second law of thermodynamics and thermodynamical equilibrium are also investigated.
PubDate: Mon, 19 Jan 2015 09:38:10 +000
- Null Geodesics and Gravitational Lensing in a Nonsingular Spacetime
Abstract: The null geodesics and gravitational lensing in a nonsingular spacetime are investigated. According to the nature of the null geodesics, the spacetime is divided into several cases. In the weak deflection limit, we find the influence of the nonsingularity parameter on the positions and magnifications of the images is negligible. In the strong deflection limit, the coefficients and observables for the gravitational lensing in a nonsingular black hole background and a weakly nonsingular spacetime are obtained. Comparing these results, we find that, in a weakly nonsingular spacetime, the relativistic images have smaller angular position and relative magnification but larger angular separation than those of a nonsingular black hole. These results might offer a way to probe the spacetime nonsingularity parameter and put a bound on it by the astronomical instruments in the near future.
PubDate: Tue, 13 Jan 2015 12:28:07 +000
- Toy Models of Universe with an Effective Varying -Term in Lyra Manifold
Abstract: Research on the accelerated expansion of our Universe captures a lot of attention. The dark energy (DE) is a way to explain it. In this paper we will consider scalar field quintessence DE with EoS, where the dynamics of the DE models related to the dynamics of the scalar field. We are interested in the study of the behavior of the Universe in the presence of interacting quintessence DE models in Lyra manifold with a varying . In a considered framework we also would like to propose a new form for . We found that the models correspond to the transit Universe, which will enter the accelerated expansion phase and will remain there with a constant deceleration parameter . We found also that the is a decreasing function which takes a small positive value with and dominating in the old Universe. Observational constraints are applied and causality issue via is discussed as a possible way to either reject or accept the models.
PubDate: Mon, 12 Jan 2015 13:50:35 +000
- BPS Center Vortices in Nonrelativistic Gauge Models with Adjoint Higgs
Abstract: We propose a class of Yang-Mills models, with adjoint Higgs fields, that accept BPS center vortex equations. The lack of a local magnetic flux that could serve as an energy bound is circumvented by including a new term in the energy functional. This term tends to align, in the Lie algebra, the magnetic field and one of the adjoint Higgs fields. Finally, a reduced set of equations for the center vortex profile functions is obtained (for ). In particular, BPS vortices come in three colours and three anticolours, obtained from an ansatz based on the defining representation and its conjugate.
PubDate: Thu, 08 Jan 2015 07:20:09 +000
- Constraining the Parameters of Modified Chaplygin Gas in Einstein-Aether
Abstract: We have assumed FRW model of the universe in Einstein-Aether gravity filled with dark matter and modified Chaplygin gas (MCG) type dark energy. We present the Hubble parameter in terms of some unknown parameters and observational parameters with the redshift z. From observed Hubble data (OHD) set (12 points), we have obtained the bounds of the arbitrary parameters of MCG by minimizing the test. Next due to joint analysis of BAO and CMB observations, we have also obtained the best fit values and the bounds of the parameters by fixing some other parameters. We have also taken type Ia supernovae data set (union 2 data set with 557 data points). Next due to joint analysis with SNe, we have obtained the best fit values of parameters. The best fit values and bounds of the parameters are obtained by 66%, 90%, and 99% confidence levels for OHD, OHD + BAO, OHD + BAO + CMB, and OHD + BAO + CMB + SNe joint analysis. The distance modulus against redshift z for our theoretical MCG model in Einstein-Aether gravity has been tested for the best fit values of the parameters and the observed SNe Ia union2 data sample.
PubDate: Tue, 30 Dec 2014 00:10:20 +000
- CP Violation for in QCD Factorization
Abstract: In the QCD factorization (QCDF) approach we study the direct CP violation in via the mixing mechanism. We find that the CP violation can be enhanced by double mixing when the masses of the pairs are in the vicinity of the resonance, and the maximum CP violation can reach 28%. We also compare the results from the naive factorization and the QCD factorization.
PubDate: Wed, 24 Dec 2014 00:10:14 +000
- Gurzadyan’s Problem 5 and Improvement of Softenings for
Cosmological Simulations Using the PP Method
Abstract: This paper is devoted to different modifications of two standard softenings of the gravitational attraction (namely, the Plummer and Hernquist softenings), which are commonly used in cosmological simulations based on the particle-particle (PP) method, and their comparison. It is demonstrated that some of the proposed alternatives lead to almost the same accuracy as in the case of the pure Newtonian interaction, even despite the fact that the force resolution is allowed to equal half the minimum interparticle distance. The revealed way of precision improvement gives an opportunity to succeed in solving Gurzadyan’s Problem 5 and bring modern computer codes up to a higher standard.
PubDate: Mon, 22 Dec 2014 11:16:18 +000
- Cosmic Baryon Asymmetry in Different Neutrino Mass Models with Mixing
Abstract: We investigate the comparative studies of cosmological baryon asymmetry in different neutrino mass models with and without by considering the three-diagonal form of Dirac neutrino mass matrices and the three aspects of leptogenesis, unflavoured, flavoured, and nonthermal. We found that the estimations of any models with are consistent in all the three stages of calculations of leptogenesis and the results are better than the predictions of any models without which are consistent in a piecemeal manner with the observational data in all the three stages of leptogenesis calculations. For the normal hierarchy of Type-IA with charged lepton matrix, model with and without predicts inflaton mass required to produce the observed baryon asymmetry to be GeV and GeV, and the corresponding reheating temperatures are GeV and GeV respectively. These predictions are not in conflict with the gravitino problem which required the reheating temperature to be below GeV. And these values apply to the recent discovery of Higgs boson of mass 125 GeV. One can also have the right order of relic dark matter abundance only if the reheating temperature is bounded to below GeV.
PubDate: Sun, 21 Dec 2014 07:30:02 +000
- Massive Conformal Gravity
Abstract: We construct a massive theory of gravity that is invariant under conformal transformations. The massive action of the theory depends on the metric tensor and a scalar field, which are considered the only field variables. We find the vacuum field equations of the theory and analyze its weak-field approximation and Newtonian limit.
PubDate: Sun, 14 Dec 2014 08:11:37 +000