International Journal of Modern Physics A

Life at Caltech with Murray Gell-Mann in the early 1960's is remembered. Our different paths to quarks, leading to different views of their reality, are described.

In this paper we derive a gauge fixing identity by varying the covariant gauge fixing term in in the background field method of QCD in pure gauge. Using this gauge fixing identity, we establish a relation between in QCD and in background field method of QCD in pure gauge. We show the validity of this gauge fixing identity, in general noncovariant and general Coulomb gauge fixings respectively. This gauge fixing identity is used to prove factorization theorem in QCD at high energy colliders and in nonequilibrium QCD at high energy heavy-ion colliders.

We study 't Hooft's equation for bound states in two-dimensional multicolor QCD. We consider the case of quarks with equal masses. We derive asymptotic expansions for the spectrum of mesons in different regimes and study their properties.

We analyze the constraints on the the vacuum polarization of the Standard Model gauge bosons from a minimal set of flavor observables valid for a general class of models of dynamical electroweak symmetry breaking. We will show that the constraints have a strong impact on the self-coupling and masses of the lightest spin-one resonances. Our analysis is applicable to any four and higher-dimensional extension of the Standard Model reducing to models of dynamical electroweak symmetry breaking.

In the usual holographic approach to QCD, the meson spectrum is generated due to a nontrivial five-dimensional background. We propose an alternative five-dimensional scenario in which the spectrum emerges due to coupling to a scalar field whose condensation is supposed to be dual to the formation of gluon condensate and mimics the scale anomaly in QCD. The spectrum of model has finite number of discrete states plus continuum and reveals a Regge-like behavior in the strong coupling regime.

The approximated energy eigenvalues and the corresponding eigenfunctions of the spherical Woods–Saxon effective potential in D dimensions are obtained within the new improved quantization rule for all l-states. The Pekeris approximation is used to deal with the centrifugal term in the effective Woods–Saxon potential. The interdimensional degeneracies for various orbital quantum number l and dimensional space D are studied. The solutions for the Hulthén potential, the three-dimensional (D = 3), the s-wave (l = 0) and the cases are briefly discussed.

Ultra-High Energy Cosmic Rays (UHECR) (E ≥ 5 × 10¹⁹eV) are detected through Extensive Air Showers that are created when a primary cosmic ray particle interacts with the atmosphere of the Earth. The energy of the primary particle can be estimated experimentally based on simulations. In this paper, we attempt to estimate the energy of UHECR gamma ray photons by applying a Monte Carlo simulation code and we compare the results with the ones derived in our previous papers for hadron initiated showers. The scenario of simulations is adapted to the P. Auger Observatory site.

The near-horizon geometry of the extremal four-dimensional Kerr black hole and certain generalizations thereof has an SL(2, ℝ) × U(1) isometry group. Excitations around this geometry can be controlled by imposing appropriate boundary conditions. For certain boundary conditions, the U(1) isometry is enhanced to a Virasoro algebra. Here, we propose a free-field construction of this Virasoro algebra.

The fluid models mentioned in the title are studied in a modified approach, based on two formulas for the mass function. All characteristics of the fluid are expressed through a master potential, satisfying an ordinary second-order differential equation. Different constraints are imposed on this core of relations, finding new solutions and deriving the classical results for perfect fluids as particular cases. All charged anisotropic solutions, all conformally flat and all uniform density solutions are found. A large class of solutions with linear equation among the two pressures is derived, including the case of vanishing tangential pressure. The mechanism responsible for the appearance of equation of state is elucidated.

In the present paper, nonconformal spherical symmetric perfect fluid solutions to Einstein field equations are obtained by using the invariance of the equations under the Lie group of transformations and some new solutions of this category are obtained satisfying the reality conditions like ρ ≥ p ≥ 0, ρ_r < 0, p_r < 0 (p and ρ being pressure and energy-density respectively) in the region 0 < r < a. Such fluids do not represent isolated fluid spheres as pressure free interface is not possible for nonconformally perfect fluids of class one.