1,580 research outputs found
Quantum Field Theory and Differential Geometry
We introduce the historical development and physical idea behind topological
Yang-Mills theory and explain how a physical framework describing subatomic
physics can be used as a tool to study differential geometry. Further, we
emphasize that this phenomenon demonstrates that the interrelation between
physics and mathematics have come into a new stage.Comment: 29 pages, enlarged version, some typewritten mistakes have been
corrected, the geometric descrition to BRST symmetry, the chain of descent
equations and its application in TYM as well as an introduction to R-symmetry
have been added, as required by mathematicia
Anomaly-Induced Magnetic Screening in 2+1 dimensional QED at Finite Density
We show that in 2+1 dimensional Quantum Electrodynamics an external magnetic
field applied to a finite density of massless fermions is screened, due to a
-dimensional realization of the underlying -dimensional axial anomaly
of the space components of the electric current. This is shown to imply
screening of the magnetic field, i.e., the Meissner effect. We discuss the
physical implications of this result.Comment: 8 pages, DFTT-93-10 [ Eq.(15) and (16) were scrambled in previous
version
An Update on Tectonics
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109300/1/eost2014EO420009.pd
Induced Parity Breaking Term at Finite Temperature
We compute the exact induced parity-breaking part of the effective action for
2+1 massive fermions in at finite temperature by calculating the
fermion determinant in a particular background. The result confirms that gauge
invariance of the effective action is respected even when large gauge
transformations are considered.Comment: to be published in Physical Review Letters. 5 pages, Revtex, no
figure
Fixed Charge Ensembles and Parity Breaking Terms
Recently derived results for the exact induced parity-breaking term in 2+1
dimensions at finite temperature are shown to be relevant to the determination
of the free energy for fixed-charge ensembles. The partition functions for
fixed total charge corresponding to massive fermions in the presence of Abelian
and non-Abelian magnetic fields are discussed. We show that the presence of the
induced Chern-Simons term manifests itself in that the free energy depends
strongly on the relation between the external magnetic flux and the value of
the fixed charge.Comment: 10 pages, Revte
Suppression of Bremsstrahlung at Non-Zero Temperature
The first-order bremsstrahlung emission spectrum is
at zero temperature. If the radiation is emitted into a region that contains a
thermal distribution of photons, then the rate is increased by a factor
where is the Bose-Einstein function. The stimulated
emission changes the spectrum to for . If this were correct, an infinite amount of energy would be radiated in the
low frequency modes. This unphysical result indicates a breakdown of
perturbation theory. The paper computes the bremsstrahlung rate to all orders
of perturbation theory, neglecting the recoil of the charged particle. When the
perturbation series is summed, it has a different low-energy behavior. For
, the spectrum is independent of and has a value
proportional to .Comment: 16 pages (plain TeX), figures available on reques
Gauge Invariance, Finite Temperature and Parity Anomaly in D=3
The effective gauge field actions generated by charged fermions in
and can be made invariant under both small and large gauge
transformations at any temperature by suitable regularization of the Dirac
operator determinant, at the price of parity anomalies. We resolve the paradox
that the perturbative expansion is not invariant, as manifested by the
temperature dependence of the induced Chern-Simons term, by showing that large
(unlike small) transformations and hence their Ward identities, are not
perturbative order-preserving. Our results are illustrated through concrete
examples of field configurations.Comment: 4 pages, RevTe
Role of spatial anisotropy in design storm generation: Experiment and interpretation
Rainfall accumulation depths over a given area are strongly dependent on the shape of the storm together with its direction of advection. A method to produce design storms exhibiting anisotropic spatial scaling is presented by combining a state-of-the-art stochastic rainfall generator STEPS with the linear generalized scale invariance (GSI) notation. The enhanced model is used to create ensembles of design storms based on an extreme storm with a distinct rainband shape observed in Melbourne, Australia. Design storms are generated both with and without accounting for anisotropy. Effect of anisotropy on precipitation characteristics is studied using the entire region covered by the radar (radar scale) and at a significantly smaller catchment scale. A rainfall-runoff model is applied to route the rainfall through the catchment into streamflow. Accounting for anisotropy allows for a more realistic description of precipitation features at the radar scale. At the catchment scale, anisotropy increases the probability of high rainfall accumulations, which translates into greater flood volumes. No discernible difference was observed in streamflow characteristics after controlling for the accumulation over the catchment. This could be explained by a lower importance of anisotropy relative to other factors affecting streamflow generation, and by the difficulties in creating representative rainfall temporal properties at the catchment scale when the radar scale is used for model calibration. The proposed method provides a tool to create ensembles of design storms when the anisotropic shape of the fields is of importance.Peer reviewe
Thermal Fluctuations of Induced Fermion Number
We analyze the phemomenon of induced fermion number at finite temperature. At
finite temperature, the induced fermion number is a thermal expectation
value, and we compute the finite temperature fluctuations, . While the zero temperature induced fermion number is
topological and is a sharp observable, the finite temperature induced fermion
number is generically nontopological, and is not a sharp observable. The
fluctuations are due to the mixing of states inherent in any finite temperature
expectation value. We analyze in detail two different cases in 1+1 dimensional
field theory: fermions in a kink background, and fermions in a chiral sigma
model background. At zero temperature the induced fermion numbers for these two
cases are very similar, but at finite temperature they are very different. The
sigma model case is generic and the induced fermion number is nontopological,
but the kink case is special and the fermion number is topological, even at
finite temperature. There is a simple physical interpretation of all these
results in terms of the spectrum of the fermions in the relevant background,
and many of the results generalize to higher dimensional models.Comment: 17 pgs, 9 figs, RevTex
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