16,694 research outputs found
Cavity QED of Strongly Correlated Electron Systems: A No-go Theorem for Photon Condensation
In spite of decades of work it has remained unclear whether or not
superradiant quantum phases, referred to here as photon condensates, can occur
in equilibrium. In this Letter, we first show that when a non-relativistic
quantum many-body system is coupled to a cavity field, gauge invariance forbids
photon condensation. We then present a microscopic theory of the cavity quantum
electrodynamics of an extended Falicov-Kimball model, showing that, in
agreement with the general theorem, its insulating ferroelectric and exciton
condensate phases are not altered by the cavity and do not support photon
condensation.Comment: Reference list updated and minor typos correcte
Meron ground states of quantum Hall droplets
We argue that topological meron excitations, which are in a strong coupling
phase (bound in pairs) in infinite quantum Hall ferromagnets, become deconfined
in finite size quantum Hall systems. Although effectively for larger systems
meron energy grows with the size of the system, when gyromagnetic ratio is
small meron becomes the lowest lying state of a quantum Hall droplet. This
comes as a consequence of the many-body correlations built in the meron
construction that minimize the interaction energy. We demonstrate this by using
mean field ansatzes for meron wave function. The ansatzes will enable us to
consider much larger system sizes than in the previous work [A. Petkovic and
M.V. Milovanovic, PRL 98, 066808 (2007)], where fractionalization into merons
was introduced.Comment: 6 pages, 6 figure
Random matrices with external source and KP functions
In this paper we prove that the partition function in the random matrix model
with external source is a KP function.Comment: 12 pages, title change
Bilayer Quantum Hall Systems at Filling Factor \nu=2: An Exact Diagonalisation Study
We present an exact diagonalisation study of bilayer quantum Hall systems at
a filling factor of two in the spherical geometry. We find the
high-Zeeman-coupling phase boundary of the broken symmetry canted
antiferromagnet is given exactly by previous Hartree-Fock mean-field theories,
but that the state's stability at weak Zeeman coupling has been qualitatively
overestimated. In the absence of interlayer tunneling, degeneracies occur
between total spin multiplets due to the Hamiltonian's invariance under
independent spin-rotations in top and bottom two-dimensional electron layers.Comment: Some remarks added in the discussion of the phase diagram, and some
typos corrected. Version to be published in Phys. Rev. Let
Evaluation of SIR-A space radar for geologic interpretation: United States, Panama, Colombia, and New Guinea
Comparisons between LANDSAT MSS imagery, and aircraft and space radar imagery from different geologic environments in the United States, Panama, Colombia, and New Guinea demonstrate the interdependence of radar system geometry and terrain configuration for optimum retrieval of geologic information. Illustrations suggest that in the case of space radars (SIR-A in particular), the ability to acquire multiple look-angle/look-direction radar images of a given area is more valuable for landform mapping than further improvements in spatial resolution. Radar look-angle is concluded to be one of the most important system parameters of a space radar designed to be used for geologic reconnaissance mapping. The optimum set of system parameters must be determined for imaging different classes of landform features and tailoring the look-angle to local topography
Management of wet grassland habitat to reduce the impact of predation on breeding waders: Phase 1. Final report
Electrical transport through a single-electron transistor strongly coupled to an oscillator
We investigate electrical transport through a single-electron transistor
coupled to a nanomechanical oscillator. Using a combination of a
master-equation approach and a numerical Monte Carlo method, we calculate the
average current and the current noise in the strong-coupling regime, studying
deviations from previously derived analytic results valid in the limit of
weak-coupling. After generalizing the weak-coupling theory to enable the
calculation of higher cumulants of the current, we use our numerical approach
to study how the third cumulant is affected in the strong-coupling regime. In
this case, we find an interesting crossover between a weak-coupling transport
regime where the third cumulant heavily depends on the frequency of the
oscillator to one where it becomes practically independent of this parameter.
Finally, we study the spectrum of the transport noise and show that the two
peaks found in the weak-coupling limit merge on increasing the coupling
strength. Our calculation of the frequency-dependence of the noise also allows
to describe how transport-induced damping of the mechanical oscillations is
affected in the strong-coupling regime.Comment: 11 pages, 9 figure
Human papillomavirus E2 regulates SRSF3 (SRp20) to promote capsid protein expression in infected differentiated keratinocytes
The human papillomavirus (HPV) life cycle is tightly linked to differentiation of the infected epithelial cell suggesting a sophisticated interplay between host cell metabolism and virus replication. Previously we demonstrated in differentiated keratinocytes in vitro and in vivo that HPV16 infection caused increased levels of the cellular SR splicing factors (SRSFs) SRSF1 (ASF/SF2), SRSF2 (SC35) and SRSF3 (SRp20). Moreover, the viral E2 transcription and replication factor that is expressed at high levels in differentiating keratinocytes could bind and control activity of the SRSF1 gene promoter. Here we reveal that E2 proteins of HPV16 and HPV31 control expression of SRSFs 1, 2 and 3 in a differentiation-dependent manner. E2 has the greatest trans-activation effect on expression of SRSF3. siRNA depletion experiments in two different models of the HPV16 life cycle (W12E and NIKS16) and one model of the HPV31 life cycle (CIN612-9E) revealed that only SRSF3 contributed significantly to regulation of late events in the virus life cycle. Increased levels of SRSF3 are required for L1 mRNA and capsid protein expression. Capsid protein expression was regulated specifically by SRSF3 and appeared independent of other SRSFs. Taken together these data suggest a significant role of the HPV E2 protein in regulating late events in the HPV life cycle through transcriptional regulation of SRSF3 expression.
IMPORTANCE Human papillomavirus replication is accomplished in concert with differentiation of the infected epithelium. Virus capsid protein expression is confined to the upper epithelial layers so as to avoid immune detection. In this study we demonstrate that the viral E2 transcription factor activates the promoter of the cellular SRSF3 RNA processing factor. SRSF3 is required for expression of the E4Ì‚L1 mRNA and so controls expression of the HPV L1 capsid protein. Thus we reveal a new dimension of virus-host interaction crucial for production of infectious virus. SRSF proteins are known drug targets. Therefore, this study provides an excellent basis for developing strategies to regulate capsid protein production in the infected epithelium and production of new virions
The decomposition of level-1 irreducible highest weight modules with respect to the level-0 actions of the quantum affine algebra
We decompose the level-1 irreducible highest weight modules of the quantum
affine algebra with respect to the level-0 --action defined in q-alg/9702024. The decomposition is
parameterized by the skew Young diagrams of the border strip type.Comment: 22 pages, AMSLaTe
Parafermions, parabosons and representations of so(\infty) and osp(1|\infty)
The goal of this paper is to give an explicit construction of the Fock spaces
of the parafermion and the paraboson algebra, for an infinite set of
generators. This is equivalent to constructing certain unitary irreducible
lowest weight representations of the (infinite rank) Lie algebra so(\infty) and
of the Lie superalgebra osp(1|\infty). A complete solution to the problem is
presented, in which the Fock spaces have basis vectors labelled by certain
infinite but stable Gelfand-Zetlin patterns, and the transformation of the
basis is given explicitly. We also present expressions for the character of the
Fock space representations
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