1,562 research outputs found
Singularities of the renormalization group flow for random elastic manifolds
We consider the singularities of the zero temperature renormalization group
flow for random elastic manifolds. When starting from small scales, this flow
goes through two particular points and , where the average value
of the random squared potential turnes negative ($l^{*}$) and where
the fourth derivative of the potential correlator becomes infinite at the
origin ($l_{c}$). The latter point sets the scale where simple perturbation
theory breaks down as a consequence of the competition between many metastable
states. We show that under physically well defined circumstances $l_{c} to negative values does not
take place.Comment: RevTeX, 3 page
The Amplitude Mode in the Quantum Phase Model
We derive the collective low energy excitations of the quantum phase model of
interacting lattice bosons within the superfluid state using a dynamical
variational approach. We recover the well known sound (or Goldstone) mode and
derive a gapped (Higgs type) mode that was overlooked in previous studies of
the quantum phase model. This mode is relevant to ultracold atoms in a strong
optical lattice potential. We predict the signature of the gapped mode in
lattice modulation experiments and show how it evolves with increasing
interaction strength.Comment: 4 pages, 3 figure
Nonequilibrium gas-liquid transition in the driven-dissipative photonic lattice
We study the nonequilibrium steady state of the driven-dissipative
Bose-Hubbard model with Kerr nonlinearity. Employing a mean-field decoupling
for the intercavity hopping , we find that the steep crossover between low
and high photon-density states inherited from the single cavity transforms into
a gasliquid bistability at large cavity-coupling . We formulate a van der
Waals like gasliquid phenomenology for this nonequilibrium situation and
determine the relevant phase diagrams, including a new type of diagram where a
lobe-shaped boundary separates smooth crossovers from sharp, hysteretic
transitions. Calculating quantum trajectories for a one-dimensional system, we
provide insights into the microscopic origin of the bistability.Comment: 5 pages, 4 figures + Supplemental Material (2 pages, 2 figures
Strong coupling theory for the Jaynes-Cummings-Hubbard model
We present an analytic strong-coupling approach to the phase diagram and
elementary excitations of the Jaynes-Cummings-Hubbard model describing a
superfluid-insulator transition of polaritons in an array of coupled QED
cavities. In the Mott phase, we find four modes corresponding to particle/hole
excitations with lower and upper polaritons, respectively. Simple formulas are
derived for the dispersion relation and spectral weights within a
strong-coupling random-phase approximation (RPA). The phase boundary is
calculated beyond RPA by including the leading correction due to quantum
fluctuations.Comment: 4 pages, 3 figures, minor changes, final version accepted for
publication in PR
Non-equilibrium delocalization-localization transition of photons in circuit QED
We show that photons in two tunnel-coupled microwave resonators each
containing a single superconduct- ing qubit undergo a sharp non-equilibrium
delocalization-localization (self-trapping) transition due to strong
photon-qubit coupling. We find that dissipation favors the self-trapped regime
and leads to the possibility of observing the transition as a function of time
without tuning any parameter of the system. Furthermore, we find that
self-trapping of photons in one of the resonators (spatial localization) forces
the qubit in the opposite resonator to remain in its initial state (energetic
localization). This allows for an easy experimental observation of the
transition by local read-out of the qubit state.Comment: 4 pages, 5 figure
Casimir Force between Vortex Matter in Anisotropic and Layered Superconductors
We present a new approach to calculate the attractive long range
vortex-vortex interaction of the van der Waals type present in anisotropic and
layered superconductors. The mapping of the statistical mechanics of vortex
lines onto the imaginary time quantum mechanics of two dimensional charged
bosons allows us to define a 2D Casimir problem: Two half-spaces of (dilute)
vortex matter separated by a gap of width R are mapped to two dielectric
half-planes of charged bosons interacting via a massive gauge field. We
determine the attractive Casimir force between the two half-planes and show,
that it agrees with the pairwise summation of the van der Waals force between
vortices previously found by Blatter and Geshkenbein [Phys. Rev. Lett. 77, 4958
(1996)]Comment: 11 pages, 3 figure
About the origin of European spelt ( Triticum spelta L.): allelic differentiation of the HMW Glutenin B1-1 and A1-2 subunit genes
To investigate the origin of European spelt (Triticum spelta L., genome AABBDD) and its relation to bread wheat (Triticum aestivum L., AABBDD), we analysed an approximately 1-kb sequence, including a part of the promoter and the coding region, of the high-molecular-weight (HMW) glutenin B1-1 and A1-2 subunit genes in 58 accessions of hexa- and tetraploid wheat from different geographical regions. Six Glu-B1-1 and five Glu-A1-2 alleles were identified based on 21 and 19 informative sites, respectively, which suggests a polyphyletic origin of the A- and B-genomes of hexaploid wheat. In both genes, a group of alleles clustered in a distinct, so-called beta subclade. High frequencies of alleles from the Glu-B1-1 and Glu-A1-2 beta subclades differentiated European spelt from Asian spelt and bread wheat. This indicates different origins of European and Asian spelt, and that European spelt does not derive from the hulled progenitors of bread wheat. The conjoint differentiation of alleles of the A- and B-genome in European spelt suggests the introgression of a tetraploid wheat into free-threshing hexaploid wheat as the origin of European spel
Vortex Entanglement and Broken Symmetry
Based on the London approximation, we investigate numerically the stability
of the elementary configurations of entanglement, the twisted-pair and the
twisted-triplet, in the vortex-lattice and -liquid phases. We find that, except
for the dilute limit, the twisted-pair is unstable and hence irrelevant in the
discussion of entanglement. In the lattice phase the twisted-triplet
constitutes a metastable, confined configuration of high energy. Loss of
lattice symmetry upon melting leads to deconfinement and the twisted-triplet
turns into a low-energy helical configuration.Comment: 4 pages, RevTex, 2 figures on reques
Scaling of the microwave magneto-impedance in TlBaCaCuO thin films
We present measurements of the magnetic field-induced microwave complex
resistivity changes at 47 GHz in TlBaCaCuO (TBCCO)
thin films, in the ranges 58 K and 00.8 T. The large
imaginary part points to strong elastic response, but the
data are not easily reconciled with a rigid vortex model. We find that, over a
wide range of temperatures, all the pairs of curves and
can be collapsed on a pair of scaling curves
, , with the same
scaling field . We argue that is related to the loss of
vortex rigidity due to a vortex transformation.Comment: Two printed pages, Proceedings of M2S (Dresden, 2006), to appear in
Physica
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