145 research outputs found
Gauge field theory for Poincar\'{e}-Weyl group
On the basis of the general principles of a gauge field theory the gauge
theory for the Poincar\'{e}-Weyl group is constructed. It is shown that tetrads
are not true gauge fields, but represent functions from true gauge fields:
Lorentzian, translational and dilatational ones. The equations of gauge fields
which sources are an energy-momentum tensor, orbital and spin momemta, and also
a dilatational current of an external field are obtained. A new direct
interaction of the Lorentzian gauge field with the orbital momentum of an
external field appears, which describes some new effects. Geometrical
interpretation of the theory is developed and it is shown that as a result of
localization of the Poincar\'{e}-Weyl group spacetime becomes a Weyl-Cartan
space. Also the geometrical interpretation of a dilaton field as a component of
the metric tensor of a tangent space in Weyl-Cartan geometry is proposed.Comment: LaTex, 27 pages, no figure
Radiatively-induced Magnetic moment in four-dimensional anisotropic QED in an external magnetic field
We discuss one-loop radiatively-induced magnetic moment in four-dimensional
quantum electrodynamics (QED) with anisotropic coupling, and examine various
cases which may be of interest in effective gauge theories of antiferromagnets,
whose planar limit coresponds to highly anisotropic QED couplings. We find a
different scaling with the magnetic field intensity in case there are extra
statistical gauge interactions in the model with spontaneous symmetry breaking.
Such a case is encountered in the CP-1 sigma-model sector of effective
spin-charge separated gauge theories of antiferromagnetic systems. Our work
provides therefore additional ways of possible experimental probing of the
gauge nature of such systems.Comment: 14 pages Latex, no figure
Free Energy of an SU(2) Model of (2+1)-dimensional QCD in the Constant Condensate Background
Gluon and quark contributions to the thermodynamic potential (free energy) of
a (2+1)-dimensional QCD model at finite temperature in the background of a
constant homogeneous chromomagnetic field H combined with A_0 condensate are
calculated. The role of the tachyonic mode in the gluon energy spectrum is
discussed. A possibility of the free energy global minimum generation at
nonzero values of H and A_0 condensates is investigated.Comment: LaTeX 2e, 14 pages, 6 eps figures, some miscalculations were
correcte
Magnetic catalysis in QED_3 at finite temperature: beyond the constant mass approximation
We solve the Schwinger-Dyson equations for (2+1)-dimensional QED in the
presence of a strong external magnetic field. The calculation is done at finite
temperature and the fermionic self energy is not supposed to be
momentum-independent, which is the usual simplification in such calculations.
The phase diagram in the temperature-magnetic field plane is determined. For
intermediate magnetic fields the critical temperature turns out to have a
square root dependence on the magnetic field, but for very strong magnetic
fields it approaches a B-independent limiting value.Comment: 21 pages, 10 figures, published versio
Plasmonic nanoparticle monomers and dimers: From nano-antennas to chiral metamaterials
We review the basic physics behind light interaction with plasmonic
nanoparticles. The theoretical foundations of light scattering on one metallic
particle (a plasmonic monomer) and two interacting particles (a plasmonic
dimer) are systematically investigated. Expressions for effective particle
susceptibility (polarizability) are derived, and applications of these results
to plasmonic nanoantennas are outlined. In the long-wavelength limit, the
effective macroscopic parameters of an array of plasmonic dimers are
calculated. These parameters are attributable to an effective medium
corresponding to a dilute arrangement of nanoparticles, i.e., a metamaterial
where plasmonic monomers or dimers have the function of "meta-atoms". It is
shown that planar dimers consisting of rod-like particles generally possess
elliptical dichroism and function as atoms for planar chiral metamaterials. The
fabricational simplicity of the proposed rod-dimer geometry can be used in the
design of more cost-effective chiral metamaterials in the optical domain.Comment: submitted to Appl. Phys.
The quantum Hall effect in graphene samples and the relativistic Dirac effective action
We study the Euclidean effective action per unit area and the charge density
for a Dirac field in a two--dimensional spatial region, in the presence of a
uniform magnetic field perpendicular to the 2D--plane, at finite temperature
and density. In the limit of zero temperature we reproduce, after performing an
adequate Lorentz boost, the Hall conductivity measured for different kinds of
graphene samples, depending upon the phase choice in the fermionic determinant.Comment: Conclusions extended. References added. 9 pages. 1 figur
Large N dynamics in QED in a magnetic field
The expression for the dynamical mass of fermions in QED in a magnetic field
is obtained for a large number of the fermion flavor N in the framework of 1/N
expansion. The existence of a threshold value N_{thr}, dividing the theories
with essentially different dynamics, is established. For the number of flavors
N << N_{thr}, the dynamical mass is very sensitive to the value of the coupling
constant \alpha_b, related to the magnetic scale \mu = |eB|. For N of order
N_{thr} or larger, a dynamics similar to that in the Nambu-Jona-Lasinio model
with cutoff of order |eB| and the dimensional coupling constant G \sim
1/(N|eB|) takes place. In this case, the value of the dynamical mass is
essentially \alpha_b independent (the dynamics with an infrared stable fixed
point). The value of N_{thr} separates a weak coupling dynamics (with
\tilde{\alpha}_b \equiv N\alpha_b << 1) from a strong coupling one (with
\tilde{\alpha}_b \gtrsim 1) and is of order 1/\alpha_b.Comment: 4 pages, REVTe
Design, installation and commissioning of the upper divertor cryopump system in Alcator C-Mod
Inherent polarization entanglement generated from a monolithic semiconductor chip
Creating miniature chip scale implementations of optical quantum information
protocols is a dream for many in the quantum optics community. This is largely
because of the promise of stability and scalability. Here we present a
monolithically integratable chip architecture upon which is built a photonic
device primitive called a Bragg reflection waveguide (BRW). Implemented in
gallium arsenide, we show that, via the process of spontaneous parametric down
conversion, the BRW is capable of directly producing polarization entangled
photons without additional path difference compensation, spectral filtering or
post-selection. After splitting the twin-photons immediately after they emerge
from the chip, we perform a variety of correlation tests on the photon pairs
and show non-classical behaviour in their polarization. Combined with the BRW's
versatile architecture our results signify the BRW design as a serious
contender on which to build large scale implementations of optical quantum
processing devices
Magnetic Catalysis: A Review
We give an overview of the magnetic catalysis phenomenon. In the framework of
quantum field theory, magnetic catalysis is broadly defined as an enhancement
of dynamical symmetry breaking by an external magnetic field. We start from a
brief discussion of spontaneous symmetry breaking and the role of a magnetic
field in its a dynamics. This is followed by a detailed presentation of the
essential features of the phenomenon. In particular, we emphasize that the
dimensional reduction plays a profound role in the pairing dynamics in a
magnetic field. Using the general nature of underlying physics and its
robustness with respect to interaction types and model content, we argue that
magnetic catalysis is a universal and model-independent phenomenon. In support
of this claim, we show how magnetic catalysis is realized in various models
with short-range and long-range interactions. We argue that the general nature
of the phenomenon implies a wide range of potential applications: from certain
types of solid state systems to models in cosmology, particle and nuclear
physics. We finish the review with general remarks about magnetic catalysis and
an outlook for future research.Comment: 37 pages, to appear in Lect. Notes Phys. "Strongly interacting matter
in magnetic fields" (Springer), edited by D. Kharzeev, K. Landsteiner, A.
Schmitt, H.-U. Yee. Version 2: references adde
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