20,213 research outputs found
On the Strong Homotopy Lie-Rinehart Algebra of a Foliation
It is well known that a foliation F of a smooth manifold M gives rise to a
rich cohomological theory, its characteristic (i.e., leafwise) cohomology.
Characteristic cohomologies of F may be interpreted, to some extent, as
functions on the space P of integral manifolds (of any dimension) of the
characteristic distribution C of F. Similarly, characteristic cohomologies with
local coefficients in the normal bundle TM/C of F may be interpreted as vector
fields on P. In particular, they possess a (graded) Lie bracket and act on
characteristic cohomology H. In this paper, I discuss how both the Lie bracket
and the action on H come from a strong homotopy structure at the level of
cochains. Finally, I show that such a strong homotopy structure is canonical up
to isomorphisms.Comment: 41 pages, v2: almost completely rewritten, title changed; v3:
presentation partly changed after numerous suggestions by Jim Stasheff,
mathematical content unchanged; v4: minor revisions, references added. v5:
(hopefully) final versio
Entanglement entropy for the long range Ising chain
We consider the Ising model in a transverse field with long-range
antiferromagnetic interactions that decay as a power law with their distance.
We study both the phase diagram and the entanglement properties as a function
of the exponent of the interaction. The phase diagram can be used as a guide
for future experiments with trapped ions. We find two gapped phases, one
dominated by the transverse field, exhibiting quasi long range order, and one
dominated by the long range interaction, with long range N\'eel ordered ground
states. We determine the location of the quantum critical points separating
those two phases. We determine their critical exponents and central-charges. In
the phase with quasi long range order the ground states exhibit exotic
corrections to the area law for the entanglement entropy coexisting with gapped
entanglement spectra.Comment: 5 pages, all comments welcom
Optical Rogue Waves in Vortex Turbulence
We present a spatio-temporal mechanism for producing 2D optical rogue waves
in the presence of a turbulent state with creation, interaction and
annihilation of optical vortices. Spatially periodic structures with bound
phase lose stability to phase unbound turbulent states in complex Ginzburg-
Landau and Swift-Hohenberg models with external driving. When the pumping is
high and the external driving is low, synchronized oscillations are unstable
and lead to spatio-temporal turbulence with high excursions in amplitude.
Nonlinear amplification leads to rogue waves close to turbulent optical
vortices, where the amplitude tends to zero, and to probability distribution
functions with long tails typical of extreme optical events.Comment: 5 pages, 7 figure
Effect of intraoperative constant rate infusion of lidocaine on short-term survival of dogs with septic peritonitis: 75 cases (2007-2011)
OBJECTIVE To investigate whether intraoperative administration of a lidocaine infusion to dogs with septic peritonitis was associated with short-term (48 hours) survival after surgery. DESIGN Retrospective case series. ANIMALS 75 dogs with septic peritonitis. PROCEDURES Medical records of dogs with septic peritonitis that underwent laparotomy between January 2007 and December 2011 at the Royal Veterinary College were reviewed. Select variables during the preoperative, intraoperative, and postoperative periods and short-term survival after surgery were compared between dogs that received an opioid only (group O; n = 33) and dogs that received lidocaine (50 \u3bcg/kg/min [22.7 \u3bcg/kg/min], IV; group L; 42) in addition to an opioid during surgery. RESULTS The proportion of dogs that survived for 48 hours after surgery was significantly greater for group L (35/42) than for group O (20/33). Intraoperative infusion of lidocaine increased the odds of short-term survival (OR, 8.77; 95% CI, 1.94 to 39.57). No significant differences were observed between the 2 treatment groups for variables assessed during the preoperative and postoperative periods. During the intraoperative period, more dogs in group L received an IV bolus of a synthetic colloid than did dogs in group O, but the number of IV boluses administered was not associated with short-term survival. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that IV infusion of lidocaine might improve the short-term survival of dogs with septic peritonitis. Prospective clinical trials are necessary to determine the efficacy of lidocaine as a supportive treatment for dogs with septic peritonitis
Searching for circumplanetary disks around LkCa 15
We present Karl G. Jansky Very Large Array (VLA) observations of the 7 mm
continuum emission from the disk surrounding the young star LkCa 15. The
observations achieve an angular resolution of 70 mas and spatially resolve the
circumstellar emission on a spatial scale of 9 AU. The continuum emission
traces a dusty annulus of 45 AU in radius that is consistent with the dust
morphology observed at shorter wavelengths. The VLA observations also reveal a
compact source at the center of the disk, possibly due to thermal emission from
hot dust or ionized gas located within a few AU from the central star. No
emission is observed between the star and the dusty ring, and, in particular,
at the position of the candidate protoplanet LkCa 15 b. By comparing the
observations with theoretical models for circumplanetary disk emission, we find
that if LkCa~15~b is a massive planet (>5 M_J) accreting at a rate greater than
1.e-6 M_J yr^{-1}, then its circumplanetary disk is less massive than 0.1 M_J,
or smaller than 0.4 Hill radii. Similar constraints are derived for any
possible circumplanetary disk orbiting within 45 AU from the central star. The
mass estimate are uncertain by at least one order of magnitude due to the
uncertainties on the mass opacity. Future ALMA observations of this system
might be able to detect circumplanetary disks down to a mass of 5.e-4 M_J and
as small as 0.2 AU, providing crucial constraints on the presence of giant
planets in the act of forming around this young star.Comment: Accepted for publication on Ap
B2 and G2 Toda systems on compact surfaces: a variational approach
We consider the B2 and G2 Toda systems on compact surfaces. We attack the
problem using variational techniques. We get existence and multiplicity of
solutions under a topological assumption on the surface and some generic
conditions on the parameters. We also extend some of the results to the case of
general systems.Comment: 28 pages, accepted on Journal of Mathematical Physic
Kovacs Effect in a Fragile Glass Model
The Kovacs protocol, based on the temperature shift experiment originally
conceived by A.J. Kovacs for glassy polymers, is implemented in an exactly
solvable dynamical model. This model is characterized by interacting fast and
slow modes represented respectively by spherical spins and harmonic oscillator
variables. Due to this fundamental property, the model reproduces the
characteristic non-monotonic evolution known as the ``Kovacs effect'', observed
in polymers, in granular materials and models of molecular liquids, when
similar experimental protocols are implemented.Comment: 8 pages, 6 figure
Conformal Gravity with Electrodynamics for Fermion Fields and their Symmetry Breaking Mechanism
In this paper we consider an axial torsion to build metric-compatible
connections in conformal gravity, with gauge potentials; the geometric
background is filled with Dirac spinors: scalar fields with suitable potentials
are added eventually. The system of field equations is worked out to have
torsional effects converted into spinorial self-interactions: the massless
spinors display self-interactions of a specific form that gives them the
features they have in the non-conformal theory but with the additional
character of renormalizability, and the mechanisms of generation of mass and
cosmological constants become dynamical. As a final step we will address the
cosmological constant and coincidence problems.Comment: 13 page
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