18219085
Background field quantization and non-commutative QED
We quantize non-commutative QED canonically in the background field gauge for weak and slowly varying background fields. We determine the complete basis for expansion under such an approximation. As an application, we derive the Wigner function which determines the leading order high temperature behavior of the perturbative amplitudes of non-commutative QED. To leading order, we also give a closed form expression for the distribution function for non-commutative QED at high temperature.
119493925
Kontsevich product and gauge invariance
We analyze the question of ${U}_{\ensuremath{\star}}(1)$ gauge invariance in a flat noncommutative space where the parameter of noncommutativity, ${\ensuremath{\theta}}^{\ensuremath{\mu}\ensuremath{\nu}}(x),$ is a local function satisfying the Jacobi identity (and thereby leading to an associative Kontsevich product). We show that in this case both gauge transformations as well as the definitions of covariant derivatives have to be modified so as to have a gauge invariant action. We work out the gauge invariant actions for the matter fields in the fundamental and the adjoint representations up to order ${\ensuremath{\theta}}^{2}$ while we discuss the gauge invariant Maxwell theory up to order $\ensuremath{\theta}.$ We show that, despite the modifications in the gauge transformations, the covariant derivative, and the field strength, the Seiberg-Witten map continues to hold for this theory. In this theory, translations do not form a subgroup of the gauge transformations (unlike in the case when ${\ensuremath{\theta}}^{\ensuremath{\mu}\ensuremath{\nu}}$ is a constant) which is reflected in the stress tensor not being conserved.
119327271
Duality, monodromy, and integrability of two dimensional string effective action
The monodromy matrix $\mathcal{M}^$ is constructed for the two dimensional tree level string effective action. The pole structure of $\mathcal{M}^$ is derived using its factorizability property. It is found that the monodromy matrix transforms nontrivially under the noncompact T-duality group, which leaves the effective action invariant, and this can be used to construct the monodromy matrix for more complicated backgrounds starting from simpler ones. We construct, explicitly, $\mathcal{M}^$ for the exactly solvable Nappi-Witten model, both when $B=0$ and $B\ensuremath{\ne}0,$ where these ideas can be directly checked. We consider well known charged black hole solutions in the heterotic string theory that can be generated by T-duality transformations from a spherically symmetric ``seed'' Schwarzschild solution. We construct the monodromy matrix for the Schwarzschild black hole background of the heterotic string theory.
119290439
An alternative construction of the positive inner product in non-Hermitian quantum mechanics
Within the context of non-Hermitian quantum mechanics, we use the generators of eigenvectors of the Hamiltonian to construct a unitary inner product space. Such models have been of interest in recent years, for instance, in the context of PT symmetry, although our construction extends to the larger class of so-called pseudo-Hermitian operators. We provide a detailed example to illustrate the concept and compare with known results.
15910786
Supersymmetric polytropic gas dynamics
Abstract We construct the N =1 supersymmetric extension of the polytropic gas dynamics. We give both the Lagrangian as well as the Hamiltonian description of this system. We construct the infinite set of ‘‘ Eulerian" conserved charges associated with this system and show that they are in involution, thereby proving complete integrability of this system. We construct the SUSY-B extension of this system as well and comment on the similarities and differences between this system and an earlier construction of the supersymmetric Chaplygin gas. We also derive the N =1 supersymmetric extension of the elastic medium equations, which, however, do not appear to be integrable.
118370691
Infrared chiral anomaly at finite temperature
Abstract We study the Schwinger model at finite temperature and show that a temperature dependent chiral anomaly may arise from the long distance behavior of the electric field. At high temperature this anomaly depends linearly on the temperature T and is present not only in the two point function, but also in all even point amplitudes.
119117986
Aharonov-Bohm effect in a class of noncommutative theories
The Aharonov-Bohm effect including spin-noncommutative effects is considered. At linear order in $\theta$, the magnetic field is gauge invariant although spatially strongly anisotropic. Despite this anisotropy, the Schr\"odinger-Pauli equation is separable through successive unitary transformations and the exact solution is found. The scattering amplitude is calculated and compared with the usual case. In the noncommutative Aharonov-Bohm case the differential cross section is independent of $\theta$.
122176004
New test for spontaneous breakdown of supersymmetry
We propose a new nonperturbative test for supersymmetry breaking. The test is first to break supersymmetry by introducing a lattice and then to study the behavior of the ground-state energy as a function of the lattice spacing a. We assume that as a approaches zero, E/sub 0/approx.ca/sup ..gamma../, where c is a nonzero constant and ..gamma.. is a critical exponent. If ..gamma.. is positive as a..-->..0, the ground-state energy of the continuum theory is zero and the theory is supersymmetric. On the other hand, if ..gamma.. is zero or negative, then supersymmetry is broken. We verify this test in the context of supersymmetric quantum mechanics using a strong-coupling expansion to calculate E/sub 0/ and ..gamma... We find that for the supersymmetric version of g/sup 2/x/sup 6/ quantum mechanics, ..gamma.. = 1.16 +- 0.02, whereas ..gamma.. is consistent with zero when we consider the supersymmetric extension of g/sup 2/x/sup 4/ theory.
121691299
Strong-coupling approximation in supersymmetric field theory
Abstract We show how to use the lattice strong-coupling approximation in a wide class of two-dimensional supersymmetric field theories. We demonstrate that this technique is highly accurate for supersymmetric theories by calculating the ground-state energy density E 0 through seventh order in perturbation theory and by showing that the result approaches the correct supersymmetric limit E 0 =0. We argue that, by their nature, strong-coupling methods are especially well-suited for practical calculation in supersymmetric theories.
54868535
The Neveu-Schwarz-Ramond string in background fields: nilpotency of BRST charge
The Neveu-Schwarz-Ramond type II closed superstring is quantized in the BRST hamiltonian formalism in the presence of arbitrary background fields. Batalin, Fradkin and Vilkovisky technique is employed in order to construct the BRST charge. The background field equations of motion are derived from the requirement of the nilpotency of the quantum BRST charge.
119502016
Dispersion relations for the self-energy in noncommutative field theories
We study the IR/UV connection in non-commutative $\phi^{3}$ theory as well as in non-commutative QED from the point of view of the dispersion relation for the self-energy. We show that, although the imaginary part of the self-energy is well behaved as the parameter of non-commutativity vanishes, the real part becomes divergent as a consequence of the high energy behavior of the dispersion integral. Some other interesting features that arise from this analysis are also briefly discussed.