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.
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.
14433188
Thermal giant graviton with non-commutative dipole field
Using the type II near-extremal 3D-branes solution we apply the T-duality and smeared twist to construct the supergravity backgrounds which dual to the 4D finite temperature non-commutative dipole field theories. We first consider the zero-temperature system in which, depending on the property of dipole vectors it may be N=2, N=1 or N=0 theory. We investigate the rotating D3-brane configurations moving on the spactimes and show that, for the cases of N=2 and N =1 the rotating D3-brane could be blowed up to the stable spherical configuration which is called as giant graviton and has a less energy than the point-like graviton. The giant graviton configuration is stable only if its angular momentum was less than a critical value of Pc which is an increasing function of the dipole strength. For the case of non-supersymmetric theory, however, the spherical configuration has a larger energy than the point-like graviton. We also find that the dipole field always render the dual giant graviton to be more stable than the point-like graviton. The relation of dual giant graviton energy with its angular momentum, which in the AdS/CFT correspondence being the operator anomalous dimension is obtained. We furthermore show that the temperature does not change the property of the giant graviton, while it will render the dual giant graviton to be unstable.
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.
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.
32279311
Hadronic wave functions in D and B decays.
We propose meson wave functions and discuss their properties, such as the moments and the average transverse momenta. We also modify the Bauer-Stech-Wirbel (BSW) model by applying these wave functions to exclusive decays of {ital D} and {ital B} mesons. Comparisons between our results and those of BSW are given. An upper limit of {ital V}{sub {ital u}{ital b}} which is smaller than that of the BSW model is found.
16523443
Heavy to light baryon transition form factors.
Recently, Stech found form factor relations for heavy to light transitions based on two simple dynamical assumptions for a spectator particle. In this paper we generalize his approach to the case of baryons and find that for ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{Q}}$\ensuremath{\rightarrow}\ensuremath{\Lambda} (Q=b or c) only one independent form factor remains in the limit ${\mathit{m}}_{\mathit{Q}}$\ensuremath{\rightarrow}\ensuremath{\infty}. Furthermore, combining with the model of Guo and Kroll we determine both of the two form factors for ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{Q}}$\ensuremath{\rightarrow}\ensuremath{\Lambda} in the heavy quark limit. The results are applied to ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}$\ensuremath{\rightarrow}\ensuremath{\Lambda}+J/\ensuremath{\psi} which is not clarified both theoretically and experimentally. It is found that the branching ratio of ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{b}}$\ensuremath{\rightarrow}\ensuremath{\Lambda}+J/\ensuremath{\psi} is of order ${10}^{\mathrm{\ensuremath{-}}5}$. \textcopyright{} 1996 The American Physical Society.
35673041
Decays of excited charmed Lambda -type and Sigma -type baryons in heavy hadron chiral perturbation theory.
Ground states and some excited p-wave states of heavy baryons are studied within the framework of heavy hadron chiral perturbation theory. The effective Lagrangian is written out to terms of the next-to-leading order in 1/${\mathit{m}}_{\mathit{Q}}$ or 1/${\mathrm{\ensuremath{\Lambda}}}_{\mathrm{\ensuremath{\chi}}}$. The coupling constants are estimated using the experimental data of \ensuremath{\Lambda} and \ensuremath{\Sigma} baryons in the static limit of the s quark. The single pion and double pion decay rates of these charmed baryons have been estimated. The numerical results show that both ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Lambda}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) are very narrow. We conclude that the two pion channel may offer the best hope for detecting the ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(3/${2}^{\mathrm{\ensuremath{-}}}$) and ${\mathrm{\ensuremath{\Sigma}}}_{\mathit{c}}$(1/${2}^{\mathrm{\ensuremath{-}}}$) p-wave doublet.
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.
73519332
RHIC Performance for FY10 200 GeV Au+Au Heavy Ion Run
Since the last successful RHIC Au+Au run in 2007 (Run-7), the RHIC experiments have made numerous detector improvements and upgrades. In order to benefit from the enhanced detector capabilities and to increase the yield of rare events in the acquired heavy ion data a significant increase in luminosity is essential. In Run-7 RHIC achieved an average store luminosity of = 12 × 10 cm−2 s−1 by operating with 103 bunches (out of 111 possible), and by squeezing to β∗ = 0.85 m. This year, Run-10, we achieved = 20 × 10 cm−2 s−1, which put us an order of magnitude above the RHIC design luminosity. To reach these luminosity levels we decreased β∗ to 0.75 m, operated with 111 bunches per ring, and reduced longitudinal and transverse emittances by means of bunched-beam stochastic cooling. In addition we introduced a lattice to suppress intra-beam scattering (IBS) in both RHIC rings, upgraded the RF control system, and separated transition crossing times in the two rings. We present an overview of the changes and the results of Run-10 performance.