17933439
Nonperturbative effects from the resummation of perturbation theory
Using the general argument in Borel resummation of perturbation theory that links the divergent perturbation theory to the nonperturbative effect we argue that the nonperturbative effect associated with the perturbation theory should have a branch cut only along the positive real axis in the complex coupling plane. The component in the weak coupling expansion of the nonperturbative amplitude, which usually includes the leading term in the weak coupling expansion, that gives rise to the branch cut can be calculated in principle from the perturbation theory combined with some exactly calculable properties of the nonperturbative effect. The realization of this mechanism is demonstrated in the double well potential and the two-dimensional O(N) nonlinear sigma model. In these models the leading term in weak coupling of the nonperturbative effect can be obtained with good accuracy from the first terms of the perturbation theory. Applying this mechanism to the infrared renormalon induced nonperturbative effect in QCD, we suggest some of the QCD condensate effects can be calculated in principle from the perturbation theory.
3172088
RAPIDITY GAP OF WEAKLY COUPLED LEPTOQUARK PRODUCTION IN ep COLLIDER
We show that the current bounds on the leptoquark couplings imply that if leptoquarks are produced in ep collisions, a significant fraction of them could form a leptoquark–quark bound state. The decay of the bound state has a distinct event shape with rapidity gap. A possible application of this observation in the leptoquark search at HERA is discussed.
119272116
Light bending by nonlinear electrodynamics under strong electric and magnetic field
We calculate the bending angles of light under the strong electric and magnetic fields by a charged black hole and a magnetized neutron star according to the nonlinear electrodynamics of Euler-Heisenberg interaction. The bending angle of light by the electric field of charged black hole is computed from geometric optics and a general formula is derived for light bending valid for any orientation of the magnetic dipole. The astronomical significance of the light bending by magnetic field of a neutron star is discussed.
119660786
Baryon number violation in dense matter. On the relation with anomalous high energy scattering
Abstract The recent claim of the equivalence of baryon number violation in dense matter and that of high energy scattering is examined. We present a plausible argument against the claim. We also calculate the anomalous decay rate of dense matter to (μ/E 0 ) 8 3 In (μ/E 0 ) order. To this order, we find the anomalous decay rate is completely equivalent to the anomalous cross section of the high energy scattering calculated by the valley method.
16719442
Chiral vacuum alignment in dense QCD
Abstract We discuss an interesting possibility of nontrivial, quark-mass induced chiral vacuum alignment in color–flavor locking phase of cold, dense QCD. With the simplifying assumption that the gaps for quarks are identical to those of antiquarks and the light quark masses are given by m u = m d and m s / m d =15, we find the true chiral vacuum can align only to one of the discrete number of directions in the continuum of chiral vacua. The alignment depends on the size of the diquark condensates, and the vacuum transitions between the discrete vacua caused by the evolution of the diquark condensates can be first order phase transition with vanishing or nonvanishing latent heat, depending on the vacua involved. It is also shown that as μ →∞, where μ is the baryon chemical potential, parity is spontaneously broken through the vacuum alignment.
14559352
Estimating higher order perturbative coefficients using Borel transform
A new method of estimating higher order perturbative coefficients is discussed. It exploits the rapid, asymptotic growth of perturbative coefficients and the information on the singularities in the complex Borel plane. A comparison with other methods is made in several Quantum Chromodynamics (QCD) expansions.
123683308
STRING THEORY AND DUALITIES IN THE QUANTUM DISSIPATIVE HOFSTADTER SYSTEM
We study the dualities of the quantum dissipative Hofstadter system which describes particles moving in two dimensions, subject to a uniform magnetic field, a periodic potential and a dissipative force. Using the string theory formulation, we show that the system has two kinds of dualities. The duality, previously known as the exact duality in the literature is shown to correspond to a subgroup of the T-dual symmetry group unbroken by the periodic boundary potential in string theory. The other duality is a particle–kink duality in the noncommutative open string theory which is a generalized Schmid duality in the presence of the uniform magnetic field. The kinks of the dissipative Hofstadter model are found to be noncommutative objects. The particle–kink duality, which is called previously the approximate duality, is shown to be also exact. In contrast to the previous derivation, which is based on the Coulomb gas expansion of the partition function and asserts that the duality holds only approximately in t...
124705504
TIME-DEPENDENT SOLUTIONS OF 5D VACUUM EINSTEIN EQUATIONS WITH COSMOLOGICAL CONSTANT
We solve vacuum field equations in five-dimensional gravity with cosmological constant to determine the time-dependence of the Robertson–Walker scale factor. We discuss its cosmological implications.
15486524
Boundary String Field Theory at One-loop
We discuss the open string one-loop partition function in tachyon condensation background of a unstable D-brane system. We evaluate the partition function by using the boundary state formulation and find that it is in complete agreement with the result obtained in the boundary string field theory. It suggests that the open string higher loop diagrams may be produced consistently by a closed string field theory, where the D-brane plays a role of source for the closed string field.
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.
16285153
Tachyon condensation and open string field theory
Abstract We perform canonical quantization of open string on a unstable D-brane in the background of tachyon condensation. Evaluating the Polyakov path-integral on a strip, we obtain a field theoretical propagator in the open string theory. As condensation occurs the string field theory is continuously deformed. At the infrared fixed point of condensation, the open string field on the unstable D-brane transmutes to that on the lower-dimensional D-brane with the correct D-brane tension.