Correlators of the Kazakov-Migdal Model

We derive loop equations for the one-link correlators of gauge and scalar fields in the Kazakov-Migdal model. These equations determine the solution of the model in the large N limit and are similar to analogous equations for the Hermitean two-matrix model. We give an explicit solution of the equations for the case of a Gaussian, quadratic potential. We also show how similar calculations in a non-Gaussian case reduce to purely algebraic equations.Comment: 14 pages, ITEP-YM-3-9

Investigations of Pairing in Anyon Systems

We investigate pairing instabilities in the Fermi-liquid-like state of a single species of anyons. We describe the anyons as Fermions interacting with a Chern-Simons gauge field and consider the weak coupling limit where their statistics approaches that of Fermions. We show that, within the conventional BCS approach, due to induced repulsive Coulomb and current-current interactions, the attractive Aharonov-Bohm interaction is not sufficient to generate a gap in the Fermion spectrum.Comment: (11 pages, 2 Figures not included

Difficulties in Inducing a Gauge Theory at Large N

It is argued that the recently proposed Kazakov-Migdal model of induced gauge theory, at large $N$, involves only the zero area Wilson loops that are effectively trees in the gauge action induced by the scalars. This retains only a constant part of the gauge action excluding plaquettes or anything like them and the gauge variables drop out.Comment: 6 pages, Latex, AZPH-TH/93-01, COLO-HEP/30

Search for Millicharged Particles at SLAC

Particles with electric charge q < 10^(-3)e and masses in the range 1--100 MeV/c^2 are not excluded by present experiments. An experiment uniquely suited to the production and detection of such "millicharged" particles has been carried out at SLAC. This experiment is sensitive to the infrequent excitation and ionization of matter expected from the passage of such a particle. Analysis of the data rules out a region of mass and charge, establishing, for example, a 95%-confidence upper limit on electric charge of 4.1X10^(-5)e for millicharged particles of mass 1 MeV/c^2 and 5.8X10^(-4)e for mass 100 MeV/c^2.Comment: 4 pages, REVTeX, multicol, 3 figures. Minor typo corrected. Submitted to Physical Review Letter

Quantum States of Topologically Massive Electrodynamics and Gravity

The free quantum states of topologically massive electrodynamics and gravity in 2+1 dimensions, are explicitly found. It is shown that in both theories the states are described by infrared-regular polarization tensors containing a regularization phase which depends on the spin. This is done by explicitly realizing the quantum algebra on a functional Hilbert space and by finding the Wightman function to define the scalar product on such a Hilbert space. The physical properties of the states are analyzed defining creation and annihilation operators. For both theories, a canonical and covariant quantization procedure is developed. The higher order derivatives in the gravitational lagrangian are treated by means of a preliminary Dirac procedure. The closure of the Poincar\'e algebra is guaranteed by the infrared-finiteness of the states which is related to the spin of the excitations through the regularization phase. Such a phase may have interesting physical consequences.Comment: 21 page, latex, no figure

Z_N Phases in Hot Gauge Theories

We argue that the \zn phases of hot gauge theories cannot be realized as a real system with an Hermitean density matrix.Comment: 7 page

An apparatus to search for mirror dark matter via the invisible decay of orthopositronium in vacuum

Mirror matter is a possible dark matter candidate. It is predicted to exist if parity is an unbroken symmetry of the vacuum. The existence of the mirror matter, which in addition to gravity is coupled to our world through photon-mirror photon mixing, would result in orthopositronium (o-Ps) to mirror orthopositronium (o-Ps') oscillations. The experimental signature of this effect is the invisible decay of o-Ps in vacuum. This paper describes the design of the new experiment for a search for the o-Ps -> invisible decay in vacuum with a sensitivity in the branching ratio of Br(o-Ps -> invisible)\simeq 10^{-7}, which is an order of magnitude better than the present limit on this decay mode from the Big Bang Nucleosynthesis. The experiment is based on a high-efficiency pulsed slow positron beam, which is also applicable for other experiments with o-Ps, and (with some modifications) for applied studies. Details of the experimental design and of a new pulsing method, as well as preliminary results on requirements for the pulsed beam components are presented. The effects of o-Ps collisions with the cavity walls as well as the influence of external fields on the o-Ps to o-Ps' oscillation probability are also discussed.Comment: 28 pages, 8 figure

Narrowing the window for millicharged particles by CMB anisotropy

We calculate the cosmic microwave background (CMB) anisotropy spectrum in models with millicharged particles of electric charge q\sim 10^{-6}-10^{-1} in units of electron charge. We find that a large region of the parameter space for the millicharged particles exists where their effect on the CMB spectrum is similar to the effect of baryons. Using WMAP data on the CMB anisotropy and assuming Big Bang nucleosynthesis value for the baryon abundance we find that only a small fraction of cold dark matter, Omega_{mcp}h_0^2 < 0.007 (at 95% CL), may consists of millicharged particles with the parameters (charge and mass) from this region. This bound significantly narrows the allowed range of the parameters of millicharged particles. In models without paraphoton millicharged particles are now excluded as a dark matter candidate. We also speculate that recent observation of 511 keV gamma-rays from the Galactic bulge may be an indication that a (small) fraction of CDM is comprised of the millicharged particles.Comment: 10 pages, 3 figures; v2: journal version, references adde

Electron-electron Bound States in Parity-Preserving QED3

By considering the Higgs mechanism in the framework of a parity-preserving Planar Quantum Electrodynamics, one shows that an attractive electron-electron interaction may come out. The e-e interaction potential emerges as the non-relativistic limit of the Moller scattering amplitude and it may result attractive with a suitable choice of parameters. Numerical values of the e-e binding energy are obtained by solving the two-dimensional Schrodinger equation. The existence of bound states is to be viewed as an indicative that this model may be adopted to address the pairing mechanism in some systems endowed with parity-preservation.Comment: 6 pages, 1 table, style revte