7,702 research outputs found
Space-time translational gauge identities in Abelian Yang-Mills gravity
We derive and calculate the space-time translational gauge identities in
quantum Yang-Mills gravity with a general class of gauge conditions involving
two arbitrary parameters. These identities of the Abelian group of translation
are a generalization of Ward-Takahasi-Fradkin identities and important for
general discussions of possible renormalization of Yang-Mills gravity with
translational gauge symmetry. The gauge identities in Yang-Mills gravity with a
general class of gauge conditions are substantiated by explicit calculations.Comment: 15 pages. To be published in The European Physical Journal - Plus
(2012
Wiedemann-Franz violation in the vortex state of a d-wave superconductor
We show that the Wiedemann-Franz law is violated in the vortex state of a
d-wave superconductor at zero temperature. We use a semiclassical approach,
which includes the Doppler shift on the quasiparticles as well as the Andreev
scattering from a random distribution of vortices. We also show that the vertex
corrections to the electrical conductivity due to the anisotropy of impurity
scattering become unimportant in the presence of a sufficiently large magnetic
field.Comment: To be published in Physica C as a proceeding of M2S-HTSC Rio 200
SU(2) Calorons and Magnetic Monopoles
We investigate the self-dual Yang-Mills gauge configurations on when the gauge symmetry SU(2) is broken to U(1) by the Wilson loop. We
construct the explicit field configuration for a single instanton by the Nahm
method and show that an instanton is composed of two self-dual monopoles of
opposite magnetic charge. We normalize the moduli space metric of an instanton
and study various limits of the field configuration and its moduli space
metric.Comment: 17 pages, RevTex, 1 Figur
Modelling the potential for permafrost development on a radioactive waste geological disposal facility in Great Britain
The safety case for a geological disposal facility (GDF) for radioactive waste based in Great Britain must consider the potential impact on the repository environment of permafrost during the 1 million years following GDF closure. The depth of penetration of permafrost, defined as ground which remains at or below 0 °C for at least 2 consecutive years, has been modelled for a future climate that uses the climate of the last glacial–interglacial cycle as an analogue. Two future climates are considered; an average estimate case considered to be the best estimate of ground surface temperatures during the last glacial–interglacial cycle, and a cold estimate case considered to be an extreme cold, but plausible future climate. Maximum modelled permafrost thicknesses across Great Britain range from 20 to 180 m for the average estimate climate and 180–305 m for the cold estimate climate. The presence of ice cover is an important determinant on permafrost development. Thick permafrost evolves during long periods of cold-based ice cover and during periods of ice retreat that results in ground exposure to very cold air temperatures. Conversely, warm-based ice has an insulating effect, shielding the ground from cold air temperatures that retards permafrost development. For a GDF at a depth greater than that predicted to be directly affected by permafrost, phenomena associated with permafrost, e.g., enhanced groundwater salinity at depth, will need to be taken into account when considering the impact on the engineered and natural barriers associated with a GDF
Two-dimensional limit of exchange-correlation energy functional approximations in density functional theory
We investigate the behavior of three-dimensional (3D) exchange-correlation
energy functional approximations of density functional theory in anisotropic
systems with two-dimensional (2D) character. Using two simple models, quasi-2D
electron gas and two-electron quantum dot, we show a {\it fundamental
limitation} of the local density approximation (LDA), and its semi-local
extensions, generalized gradient approximation (GGA) and meta-GGA (MGGA), the
most widely used forms of which are worse than the LDA in the strong 2D limit.
The origin of these shortcomings is in the inability of the local (LDA) and
semi-local (GGA/MGGA) approximations to describe systems with 2D character in
which the nature of the exchange-correlation hole is very nonlocal. Nonlocal
functionals provide an alternative approach, and explicitly the average density
approximation (ADA) is shown to be remarkably accurate for the quasi-2D
electron gas system. Our study is not only relevant for understanding of the
functionals but also practical applications to semiconductor quantum structures
and materials such as graphite and metal surfaces. We also comment on the
implication of our findings to the practical device simulations based on the
(semi-)local density functional method.Comment: 21 pages including 9 figures, to be published in Phys. Rev.
The creation of large photon-number path entanglement conditioned on photodetection
Large photon-number path entanglement is an important resource for enhanced
precision measurements and quantum imaging. We present a general constructive
protocol to create any large photon number path-entangled state based on the
conditional detection of single photons. The influence of imperfect detectors
is considered and an asymptotic scaling law is derived.Comment: 6 pages, 4 figure
Marginal Deformations of Field Theories with AdS_4 Duals
We generate new AdS_4 solutions of D=11 supergravity starting from AdS_4 x
X_7 solutions where X_7 has U(1)^3 isometry. We consider examples where X_7 is
weak G_2, Sasaki-Einstein or tri-Sasakian, corresponding to d=3 SCFTs with
N=1,2 or 3 supersymmetry, respectively, and where the deformed solutions
preserve N=1,2 or 1 supersymmetry, respectively. For the special cases when X_7
is M(3,2), Q(1,1,1) or N(1,1)_I we identify the exactly marginal deformation in
the dual field theory. We also show that the volume of supersymmetric 5-cycles
of N(1,1)_I agrees with the conformal dimension predicted by the baryons of the
dual field theory.Comment: 28 pages, 2 figures; v2. typos correcte
NR duals in M-theory
We extend the search for supergravity solution duals of non-relativistic
CFTs to supergravity. We consider the internal space to be an
bundle over a product base: and . For
purely M-theoretic , we find only magnetic fluxes preserving
two supersymmetries. is far richer admitting in addition to
magnetic fluxes, various non-trivial electric fluxes which break all
supersymmetry.Comment: 18 pages, Minor corrections and added reference
Minimizing Effective Many-Body Interactions
A simple two-level model is developed and used to test the properties of
effective interactions for performing nuclear structure calculations in
truncated model spaces. It is shown that the effective many-body interactions
sensitively depend on the choice of the single-particle basis and they appear
to be minimized when a self- consistent Hartree-Fock basis is used.Comment: (15 pages of text and 1 postscript figure (Figure available upon
request), Preprint Number not assigned ye
Impact of surface discharge plasmas on performance of a metallized film capacitor
Surface breakdown discharges are one probable failure mechanism of metallized polymeric film
capacitors used in power systems, traction drives, and other technological applications. To assess
whether surface breakdown discharges may undergo considerable elongation on the electrode
surface to affect significantly capacitor performance, an equivalent electric circuit model is
developed for metallized polymer film capacitors under the thermal equilibrium condition. With the
aid of a surface field gradient mechanism, propagation of surface plasmas is studied and the
necessary condition for their possible elongation is obtained. Numerical examples of a metallized
film capacitor are used to demonstrate that surface breakdown plasmas and their elongation are
unlikely to affect capacitor performance in a significant fashion. Then the generic problem of plasma
propagation is restudied under thermally nonequilibrium conditions. Based on a heat conduction
formulation in the one-dimensional limit, a temperature gradient mechanism is proposed to explain
the possible elongation of breakdown plasmas on an electrode surface. Numerical examples are
again used to deduce that thermally nonequilibrium surface plasmas are unlikely to evolve into
catastrophic flashover arcs to fail film capacitors
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