10679146
Conformal transformation of renormalized effective action in curved spacetimes.
The functional-differential equation which governs the conformal transformation of the renormalized effective action for a massless, conformally invariant quantized field is solved exactly. The formula so obtained can be used to obtain the effective action in any background spacetime once there exists a conformally related spacetime in which the effective action is known. A simple example is presented to see how our formula is useful to obtain the renormalized stress tensor in the \ensuremath{\zeta}-functional regularization scheme.
119556809
Quantum stabilization of compact space by extra fuzzy space
We investigate the quantized scalar field on the Kaluza–Klein spacetimes of MD×Td×SFZ, where MD is the ordinary D-dimensional flat Minkowski spacetimes, Td is the d-dimensional commutative torus, and SFZ is a noncommutative fuzzy two-sphere with a fixed quantized radius. After evaluating the one-loop correction to the spectrum we use the mass-corrected term to compute the Casimir energy of the scalar field on the model spacetime. It is seen that, for some values of D and d, the Casimir energy due to vacuum fluctuation in the model spacetimes could give rise a repulsive force to stabilize the commutative torus.
13332555
Thermodynamics on noncommutative geometry in coherent state formalism
Abstract The thermodynamics of ideal gas on the noncommutative geometry in the coherent state formalism is investigated. We first evaluate the statistical interparticle potential and see that there are residual “attraction (repulsion) potential” between boson (fermion) in the high temperature limit. The characters could be traced to the fact that, the particle with mass m in noncommutative thermal geometry with noncommutativity θ and temperature T will correspond to that in the commutative background with temperature T ( 1 + k T m θ ) −1 . Such a correspondence implies that the ideal gas energy will asymptotically approach to a finite limiting value as that on commutative geometry at T θ = ( k m θ ) −1 . We also investigate the squeezed coherent states and see that they could have arbitrary mean energy. The thermal properties of those systems are calculated and compared to each other. We find that the heat capacity of the squeezed coherent states of boson and fermion on the noncommutative geometry have different values, contrast to that on the commutative geometry.
3203139
Tubular Solutions in NS5-brane, Dp-brane and Macroscopic Strings Backgrounds
We present our searches for the tubular bound states of a D2-brane with m D0-branes and n fundamental strings in the NS5-brane, Dp-brane or macroscopic strings background by solving the Dirac-Born-Infeld equation. The geometry of tubular configurations we considered are taken to be parallel to the background branes or macroscopic strings. The n fundamental strings therein may be the circular strings Fc or the straight strings Fs, which are along the cross section or the axis of the tube respectively. We show that the stable tubular bound states of (nFs, mD0, D2) which are prevented form collapse by the angular momentum, as original found in flat space, could be formed in the NS5-brane, D6-brane and macroscopic strings background. However, they becomes unstable in the D2-brane and D4-brane background. We also show that there are stable tubular bound states of (nFc, mD0, D2) and (mD0, D2), which are prevented form collapse by the gravitational forces in the backgrounds of D6-brane. We discuss the properties of these tubular solutions and see that only that in the macroscopic strings background is a supersymmetric BPS configuration.
46429286
Adiabatic regularization of the quantum stress-energy tensor in curved spacetimes: Path-integral quantization method.
A possible way to obtain the adiabatic regularized quantum stress-energy tensor in a background curved spacetime is developed within the method of path-integral quantization. As an illustration, we study the mode of a massive scalar field with arbitrary curvature coupling to the inhomogeneous conformally flat spacetime. The results so obtained are useful to investigate the back-reaction effects of a quantized field in the early Universe with an inhomogeneity.
120467733
No-go theorem of the infrared divergences generated by cosmological evolution
Abstract It is proved that in curved spacetime the infrared divergences of a free field theory cannot arise through dynamical evolution from a state which is initially free of them.
12724895
Reexamination of the perturbative pion form factor with Sudakov suppression.
The perturbative pion form factor with Sudakov suppression is reexamined. To guarantee the reliability of the perturbative calculations we suggest that the running coupling constant should be frozen at {alpha}{sub {ital s}}({ital t}={l_angle}{ital k}{sub {ital T}}{r_angle}) and {l_angle}{ital k}{sub {ital T}}{r_angle} is the average transverse momentum which can be determined by the pionic wave function. In addition we correct the previous calculations about the Sudakov suppression factor which plays an important role in the perturbative calculations for the pion form factor.
8777025
Quantum chromodynamics in background fields.
We try to build a framework for quantum chromodynamics in background fields. The nonvanishing vacuum condensates are described by the classical fields, while the corresponding quantum fields are quantized in the Furry representation and the physical states are defined in the physical QCD vacuum. The complete quark and gluon propagators are discussed in this framework and running condensate parameters are introduced by the renormalization requirement. A modified Callan-Symanzik equation is derived by taking account of the nonperturbative corrections.
37211097
Calculation of chiral-symmetry breaking and pion properties as a Goldstone boson.
A procedure for picking out the solution of the covariant Bethe-Salpeter equation corresponding to the Goldstone boson in a spontaneous-chiral-symmetry-breaking theory is described under very general assumptions. Physical quantities for chiral-symmetry breaking and the pion are calculated with this procedure taking into account gluon ladder exchange and a covariant chiral-symmetric generalization of the confinement potential. Satisfactory results are obtained with reasonable values of the parameters.
42952650
Null vectors in super Virasoro representations of the superconformal algebra.
Using the fusion procedure, a complete and straightforward algorithm for finding null vectors in Verma modules of the {ital N}=1 superconformal algebra is given.
39608513
Bethe-Salpeter wave functions for mesons of arbitrary spin and the covariant instantaneous approximation.
The most general form of the Bethe-Salpeter (BS) wave functions for mesons of arbitrary spin and definite parity is given. Using the BS equation, the constraints on the BS wave function due to assuming the covariant instantaneous approximation are found. The application of the general formalism to heavy mesons is given and, in particular, the results from the spin SU(2) symmetry of the heavy quark are naturally obtained in the infinite quark mass limit.