124303693
Effective Masses of Mesons and Nucleon in Hot Medium for the Walecka Model
Based on the thermo-field dynamics, the temperature and density dependencies of the effective masses of σ, ω mesons and nucleon in the walecka model have been calculated. The vacuum fluctuation effect is examined. It is found that the vacuum fluctuation is very important and leads to a reduction of ω-meson mass and an enhancement of σ-meson mass in hot and dense medium.
121746713
The effective mass and screening mass of the rho meson for the vector dominance model and the vector coupling model at finite temperature and density
In the framework of thermo-field dynamics, the temperature and/or density dependences of the effective mass and the screening mass of the rho -meson for the vector dominance model and the nucleon-nucleon- rho -meson (NN rho ) vector coupling model have been calculated. We have found that for the vector dominance model, the effective mass and the screening mass of the rho -meson increase with temperature, and for the NN rho vector coupling model, they remain almost unchanged with temperature, but increase with density.
32394428
Thermodynamical fluctuations of meson fields for a quantum hadrodynamics model.
Using the real-time Green's-function method with a pair-cutoff approximation up to second order, the thermodynamical fluctuation effects of meson fields on the QHD-II model are studied. We find that the fluctuation effects of meson fields, in particular, the \ensuremath{\pi} meson field, on saturation energy, effective mass of nucleon, and pressure are remarkable in the low-density region and/or high-temperature region. The results given by the QHD-I and QHD-II models are compared. The value of the critical point of the liquid-gas phase transition for the QHD-II model is given.
124938750
The effects of vacuum fluctuations on ρ meson masses in hot and dense matter
Based on the thermo field dynamics, the temperature- and density-dependent effective mass and screening mass of ρ meson in the vector–tensor ρ–meson–nucleon–nucleon coupling model have been calculated. The effects of the vacuum fluctuation corrections through the effective nucleon mass are examined. We have shown that the vacuum fluctuation gives an important correction to the self-energy of ρ meson and leads to a reduction of ρ-meson mass in hot and dense matter.
32634500
Bonn potential model at finite temperature.
By using the thermofield dynamics, we have calculated the effective coupling of nucleon-nucleon mesons by summing the three-lines vertices and the masses of nucleon and mesons by summing the corresponding self-energy diagrams of the Bonn potential model at finite temperature. Through the temperature dependence of effective couplings and the screening masses, we have extended the Bonn potential to finite temperature. {copyright} {ital 1996 The American Physical Society.}
119546468
Hawking Evaporation for the 2 + 1 Dimensional Radiating Black Hole
By using a metric which is a counterpart of four dimensional Vaidya metric, we have investigated the Hawking evaporation of the 2 + 1 dimensional radiating black hole. The Hawking temperature of this radiating black hole is given. In a specific case, our result reduces to that of Banados, Teitelboim and Zanelli's.
118387796
Majorana neutrino mass matrices with three texture zeros and the sterile neutrino
As a consequence of the LSND anomaly and other hints of an eV scale sterile neutrino from particle physics and cosmology, the neutrino sector of the standard model of particle physics has to be extended and the smallest extension is the (3+1) model, i.e. three active neutrinos plus one sterile one. In this work we study the neutrino mass matrix $M_\nu$ with three texture zeros in the (3+1) model, assuming all the neutrino states are of Majorana type. With the mass hierarchy between the active and sterile neutrinos as well as the smallness of the reactor neutrino mixing and active-sterile mixing, the analytical expressions can be greatly simplified. We systematically examine all the 120 texture zeros, via both analytical and numerical analysis, and find that the 100 textures with zeros in the fourth column and row of $M_\nu$ can hardly be compatible with experiments whereas 19 of the other 20 are feasible. We can foresee that the active neutrino masses are required to be around 0.01 eV and the next generation neutrinoless double beta decay experiments are promising to test these textures. Many other phenomenologically meaningful predictions are also obtained. All the CP conserving (3+1) textures with three zeros are excluded by experiments.
54060612
Petrov type I condition and Rindler fluid in vacuum Einstein-Gauss-Bonnet gravity
A bstractRecently the Petrov type I condition is introduced to reduce the degrees of freedom of the extrinsic curvature of a timelike hypersurface to the degrees of freedom in the dual Rindler fluid in Einstein gravity. In this paper we show that the Petrov type I condition holds for the solutions of vacuum Einstein-Gauss-Bonnet gravity up to the second order in the relativistic hydrodynamic expansion. On the other hand, if imposing the Petrov type I condition and Hamiltonian constraint on a finite cutoff hypersurface, the stress tensor of the relativistic Rindler fluid in vacuum Einstein-Gauss-Bonnet gravity can be recovered with correct first order and second order transport coefficients. The case in the non-relativistic hydrodynamic expansion is also discussed.
119113547
Petrov type I spacetime and dual relativistic fluids
The Petrov type I condition for the solutions of vacuum Einstein equations in both of the nonrelativistic and relativistic hydrodynamic expansions is checked. We show that it holds up to the third order of the nonrelativistic hydrodynamic expansion parameter, but it is violated at the fourth order even if we choose a general frame. On the other hand, it is found that the condition holds at least up to the second order of the derivative expansion parameter. Turn the logic around, through imposing the Petrov type I condition and Hamiltonian constraint on a finite cutoff surface, we show that the stress tensor of the relativistic fluid can be recovered with correct first order and second order transport coefficients dual to the solutions of vacuum Einstein equations.
119308558
Vacuum stability and Higgs diphoton decay rate in the Zee-Babu model
A bstractAlthough recent Higgs data from ATLAS and CMS are compatible with a Standard Model (SM) signal at 2σ level, both experiments see indications for an excess in the diphoton decay channel, which points to new physics beyond the SM. Given such a low Higgs mass mH ~ 125 GeV, another sign indicating the existence of new physics beyond the SM is the vacuum stability problem, i.e., the SM Higgs quartic coupling may run to negative values at a scale below the Planck scale. In this paper, we study the vacuum stability and enhanced Higgs diphoton decay rate in the Zee-Babu model, which was used to generate tiny Majorana neutrino masses at two-loop level. We find that it is rather difficult to find overlapping regions allowed by the vacuum stability and diphoton enhancement constraints. As a consequence, it is almost inevitable to introduce new ingredients into the model, in order to resolve these two issues simultaneously.
118348335
Grand Unified Yukawa Matrix Ansatz: The Standard Model Fermion Mass, Quark Mixing and CP Violation Parameters
We propose a new mass matrix ansatz: At the grand unified (GU) scale, the standard model (SM) Yukawa coupling matrix elements are integer powers of the square root of the GU gauge coupling constant ε ≡ αGU, multiplied by order unity random complex numbers. It relates the hierarchy of the SM fermion masses and quark mixings to the gauge coupling constants, greatly reducing the SM parameters, and can give good fitting results of the SM fermion mass, quark mixing and CP violation parameters. This is a neat but very effective ansatz.