5,492 research outputs found
Modular symmetry and temperature flow of conductivities in quantum Hall systems with varying Zeeman energy
The behaviour of the critical point between quantum Hall plateaux, as the
Zeeman energy is varied, is analysed using modular symmetry of the Hall
conductivities following from the law of corresponding states. Flow diagrams
for the conductivities as a function of temperature, with the magnetic field
fixed, are constructed for different Zeeman energies, for samples with
particle-hole symmetry.Comment: 15 pages, 13 figure
The design of a linear L-band high power amplifier for mobile communication satellites
A linear L-band solid state high power amplifier designed for the space segment of the Mobile Satellite (MSAT) mobile communication system is described. The amplifier is capable of producing 35 watts of RF power with multitone signal at an efficiency of 25 percent and with intermodulation products better than 16 dB below carrier
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The Venus ionosphere in the northern polar region
PLASLIFE is a computer simulation which assists in the interpretation of high latitude ionospheric observations and, in this study, is applied to the polar regions of Venus. The Venus Express spacecraft samples the high latitude ionosphere in the northern hemisphere of the planet. On 4 August 2008 it was inserted into a new orbit with pericentre located below 200 km close to 86° N. The ASPERA-4 instrument on the spacecraft records the first extended in situ data set of the plasma environment in this sector. The observed ionospheric ion and electron populations exhibit significant variation between orbits and, by compensating for the effects of solar zenith angle and altitude, the relative contributions of photoionisation and plasma transport can be investigated. These variations are discussed with respect to parameters including local time and solar flux. Comparisons are drawn with the terrestrial ionosphere
The Phase Structure of Mass-Deformed SU(2)xSU(2) Quiver Theory
The phase structure of the finite SU(2)xSU(2) theory with N=2 supersymmetry,
broken to N=1 by mass terms for the adjoint-valued chiral multiplets, is
determined exactly by compactifying the theory on a circle of finite radius.
The exact low-energy superpotential is constructed by identifying it as a
linear combination of the Hamiltonians of a certain symplectic reduction of the
spin generalized elliptic Calogero-Moser integrable system. It is shown that
the theory has four confining, two Higgs and two massless Coulomb vacua which
agrees with a simple analysis of the tree-level superpotential of the
four-dimensional theory. In each vacuum, we calculate all the condensates of
the adjoint-valued scalars.Comment: 12 pages, JHEP.cl
Exact Superpotentials from Matrix Models
Dijkgraaf and Vafa (DV) have conjectured that the exact superpotential for a
large class of N=1 SUSY gauge theories can be extracted from the planar limit
of a certain holomorphic matrix integral. We test their proposal against
existing knowledge for a family of deformations of N=4 SUSY Yang-Mills theory
involving an arbitrary polynomial superpotential for one of the three adjoint
chiral superfields. Specifically, we compare the DV prediction for these models
with earlier results based on the connection between SUSY gauge theories and
integrable systems. We find complete agreement between the two approaches. In
particular we show how the DV proposal allows the extraction of the exact
eigenvalues of the adjoint scalar in the confining vacuum and hence computes
all related condensates of the finite-N gauge theory. We extend these results
to include Leigh-Strassler deformations of the N=4 theory.Comment: 28 pages, 1 figure, latex with JHEP.cls, replaced with typos
corrected and one clarifying commen
Properties of finite Gaussians and the discrete-continuous transition
Weyl's formulation of quantum mechanics opened the possibility of studying
the dynamics of quantum systems both in infinite-dimensional and
finite-dimensional systems. Based on Weyl's approach, generalized by Schwinger,
a self-consistent theoretical framework describing physical systems
characterised by a finite-dimensional space of states has been created. The
used mathematical formalism is further developed by adding finite-dimensional
versions of some notions and results from the continuous case. Discrete
versions of the continuous Gaussian functions have been defined by using the
Jacobi theta functions. We continue the investigation of the properties of
these finite Gaussians by following the analogy with the continuous case. We
study the uncertainty relation of finite Gaussian states, the form of the
associated Wigner quasi-distribution and the evolution under free-particle and
quantum harmonic oscillator Hamiltonians. In all cases, a particular emphasis
is put on the recovery of the known continuous-limit results when the dimension
of the system increases.Comment: 21 pages, 4 figure
Family memories in the home: contrasting physical and digital mementos
We carried out fieldwork to characterise and compare physical and digital mementos in the home. Physical mementos are highly valued, heterogeneous and support different types of recollection. Contrary to expectations, we found physical mementos are not purely representational, and can involve appropriating common objects and more idiosyncratic forms. In contrast, digital mementos were initially perceived as less valuable, although participants later reconsidered this. Digital mementos were somewhat limited in function and expression, largely involving representational photos and videos, and infrequently accessed. We explain these digital limitations and conclude with design guidelines for digital mementos, including better techniques for accessing and integrating these into everyday life, allowing them to acquire the symbolic associations and lasting value that characterise their physical counterparts
Five-Dimensional Gauge Theories and Quantum Mechanical Matrix Models
We show how the Dijkgraaf-Vafa matrix model proposal can be extended to
describe five-dimensional gauge theories compactified on a circle to four
dimensions. This involves solving a certain quantum mechanical matrix model. We
do this for the lift of the N=1* theory to five dimensions. We show that the
resulting expression for the superpotential in the confining vacuum is
identical with the elliptic superpotential approach based on Nekrasov's
five-dimensional generalization of Seiberg-Witten theory involving the
relativistic elliptic Calogero-Moser, or Ruijsenaars-Schneider, integrable
system.Comment: 11 pages, 2 figures, JHEP3.cls, important references adde
Kernel functions and B\"acklund transformations for relativistic Calogero-Moser and Toda systems
We obtain kernel functions associated with the quantum relativistic Toda
systems, both for the periodic version and for the nonperiodic version with its
dual. This involves taking limits of previously known results concerning kernel
functions for the elliptic and hyperbolic relativistic Calogero-Moser systems.
We show that the special kernel functions at issue admit a limit that yields
generating functions of B\"acklund transformations for the classical
relativistic Calogero-Moser and Toda systems. We also obtain the
nonrelativistic counterparts of our results, which tie in with previous results
in the literature.Comment: 76 page
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