56316687
Quantum Brownian Motion on a Triangular Lattice and Fermi-Bose Equivalence: An Application of Boundary State Formulation
We discuss the Bose-Fermi equivalence in the quantum Brownian motion (QBM) on a triangular lattice, mapping the action for the QBM into a string theory action with a periodic boundary tachyon potential. We construct new Klein factors which are more appropriate than the conventional ones to deal with the quantum field theories defined on a two dimensioanl space-time with boundaries. Using the Fermi-Bose equivalence with the new Klein factors, we show that the model for the quantum Bownian motion on a triangular lattice is equivalent to the Thirring model with boundary terms, which are quadratic in fermion field operators, in the off-critical regions and to a SU(3) × SU(3) free fermion theory with quadratic boundary terms at the critical point.
6225872
Statistical mechanics of non-Abelian Chern-Simons particles.
We discuss the statistical mechanics of a two-dimensional gas of non-Abelian Chern-Simons particles which obey the non-Abelian braid statistics. The second virial coefficient is evaluated in the framework of the non-Abelian Chern-Simons quantum mechanics.
119489587
Fermion representation of the rolling tachyon boundary conformal field theory
A free fermion representation of the rolling tachyon boundary conformal field theory is constructed. The representation is used to obtain an explicit, compact, exact expression for the boundary state. We use the boundary state to compute the disc and cylinder amplitudes for the half-S-brane.
37673623
Apparatus-dependent contributions to g-2?
The University of Washington g-2 experiments have progressed to the marvelous precision of 10/sup 12/ in their measurement of the magnetic moment of the electron. A further improvement of a factor of 10 should occur in the near future. Concomitant with this accuracy is the necessity of understanding small corrections. These experiments employ a Penning trap whose electrodes behave as conducting walls for a microwave cavity. We investigate the effect of this cavity on the spin and cyclotron frequencies. Previous work, employing calculations that are not gauge invariant, implies that the present level of accuracy cannot be exceeded because of cavity effects on the spin precession frequency. In contrast to this erroneous work, we find no significant correction to the spin precession frequency, but we do find that the correction to the cyclotron frequency will be important when the experiments improve by another order of magnitude. 9 references.
119319846
Dissipative hofstadter model at the magic points and critical boundary sine-gordon model
The dissipative Hofstadter model describes quantum particles moving in two dimensions subject to a uniform magnetic field, a periodic potential and a dissipative force. We discuss the dissipative Hofstadter model in the framework of the boundary state formulation in string theory and construct exact boundary states for the model at the magic points by using the fermion representation. The dissipative Hofstadter model at magic points is shown to be equivalent to the critical boundary sine-Gordon model.
1624418
String field theory and perturbative dynamics of noncommutative field theory
Abstract The perturbative dynamics of noncommutative field theory (NCFT) is discussed from a point view of string field theory. As in the commutative case it is inevitable to introduce a closed string, which may be described as a bound state of two noncommutative open strings. We point out that the closed string, interacting nontrivially with the open string, plays an essential role in the ultraviolet region. The contribution of the closed string is responsible for the discrepancy between the NCFT and the string field theory. It clarifies the controversial issues associated with the ultraviolet/infrared (UV/IR) behaviour of the perturbative dynamics of the NCFT.
119286280
LIGHT BENDING IN A COULOMBIC FIELD
The nonlinear Euler–Heisenberg interaction bends light toward an electric charge. The bending angle and trajectory of light in a Coulombic field are computed in geometric optics.
122987979
Large-order behavior and nonperturbative effects
Abstract We consider the energy-dependence of the large-order behavior of forward scattering amplitudes in theories having explicit mass parameters and instanton solutions. We show that in weak coupling theories the exponential part of the Espinosa-Ringwald type cross section can be determined by taking the minimum element of the perturbative series, suggesting that the series is asymptotic. This observation enables us to calculate the nonperturbative cross section by the perturbation of the Borel transform σ (b) about the instanton-anti-instanton singularity. The anomalous cross section in the standard model using the leading energy-dependent σ (b) is presented.
14038741
Resummation of the hadronic tau decay width with the modified Borel transform method
A modified Borel transform of the Adler function is used to resum the hadronic tau decay width ratio. In contrast with the ordinary Borel transform, the integrand of the Borel integral is renormalization-scale invariant. We use an ansatz which explicitly accounts for the structure of the leading infrared renormalon. Further, we use judiciously chosen conformal transformations for the Borel variable, in order to map sufficiently away from the origin the other ultraviolet and infrared renormalon singularities. In addition, we apply Pad\'e approximants for the corresponding truncated perturbation series of the modified Borel transform, in order to further accelerate the convergence. Comparing the results with the presently available experimental data on the tau hadronic decay width ratio, we obtain ${\ensuremath{\alpha}}_{\mathrm{s}}{(M}_{\mathrm{z}}^{2})=0.1192\ifmmode\pm\else\textpm\fi{}{0.0007}_{\mathrm{exp}.}\ifmmode\pm\else\textpm\fi{}{0.0010}_{\mathrm{EW}+\mathrm{CKM}}\ifmmode\pm\else\textpm\fi{}{0.0009}_{\mathrm{th}.}\ifmmode\pm\else\textpm\fi{}{0.0003}_{\mathrm{evol}.}.$ These predictions virtually agree with those of our previous resummations where we used ordinary Borel transforms instead.
118949045
N=4 supersymmetric quantum mechanics with magnetic monopole
Abstract We propose an N = 4 supersymmetric quantum mechanics of a charged particle on a sphere in the background of Dirac magnetic monopole and study the system in the CP ( 1 ) model approach. By using the Dirac quantization method, we explicitly calculate the symmetry algebra taking the operator ordering ambiguity into consideration. We find that it is given by the superalgebra su ( 1 | 2 ) × su ( 2 ) rot . We also show that the Hamiltonian can be written in terms of the Casimir invariant of su ( 2 ) rot algebra. Using this relation and analyzing the lower bound for angular momentum, we find the energy spectrum. We, then, examine the ground energy sector to find that the N = 4 supersymmetry is spontaneously broken to N = 2 for certain values of the monopole charge.
118566101
Higher dimensional cosmological model with a phantom field
We consider a higher dimensional gravity theory with a negative kinetic energy scalar field and a cosmological constant. We find that the theory admits an exact cosmological solution for the scale factor of our universe. It has the feature that the universe undergoes a continuous transition from deceleration to acceleration at some finite time. This transition time can be interpreted as that of recent acceleration of our universe.