723 research outputs found
Massive Schwinger model with a finite inductance: theta-(in)dependence, the U(1) problem, and low-energy theorems
Gauge theories embedded into higher-dimensional spaces with certain
topologies acquire inductance terms, which reflect the energy cost of
topological charges accumulated in the extra dimensions. We compute topological
susceptibility in the strongly-coupled two-flavor massive Schwinger model with
such an inductance term and find that it vanishes, due to the contribution of a
global low-energy mode (a ``global axion''). This is in accord with the general
argument on the absence of theta-dependence in such topologies. Because the
mode is a single oscillator, there is no corresponding particle, and the
solution to the U(1) problem is unaffected.Comment: 12 pages, 1 figure; accepted to Phys. Rev.
Piezoelectric coupling, phonons, and tunneling into a quantum Hall edge
We show that the piezoelectric coupling to three-dimensional phonons in GaAs
renormalizes the current-voltage exponent for tunneling of electrons into an
incompressible quantum Hall edge. The leading correction is always negative, in
agreement with experiments on the state and, depending on the
precise value of the edge plasmon speed, can be as large as a few percent. We
also discuss higher-order corrections, which determine the effect of the
piezoelectric coupling in the extreme infrared limit.Comment: 5 page
Disoriented chiral condensate in (1+1) Lorentz-invariant geometry
We consider isospin correlations of pions produced in a relativistic nuclear
collision, using an effective theory of the chiral order parameter. Our theory
has (1+1) Lorentz invariance as appropriate for the central rapidity region. We
argue that in certain regions of space correlations of the chiral order
parameter are described by the fixed point of the (1+1) WZNW model. The
corresponding anomalous dimension determines scaling of the probability to
observe a correlated cluster of pions with the size of this cluster in
rapidity. Though the maximal size of clusters for which this scaling is
applicable is cut off by pion mass, such clusters can still include
sufficiently many particles to make the scaling observable.Comment: 9 pages, LATEX, UCLA/93/TEP/1
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