8,213 research outputs found
Jacobi structures revisited
Jacobi algebroids, that is graded Lie brackets on the Grassmann algebra
associated with a vector bundle which satisfy a property similar to that of the
Jacobi brackets, are introduced. They turn out to be equivalent to generalized
Lie algebroids in the sense of Iglesias and Marrero and can be viewed also as
odd Jacobi brackets on the supermanifolds associated with the vector bundles.
Jacobi bialgebroids are defined in the same manner. A lifting procedure of
elements of this Grassmann algebra to multivector fields on the total space of
the vector bundle which preserves the corresponding brackets is developed. This
gives the possibility of associating canonically a Lie algebroid with any local
Lie algebra in the sense of Kirillov.Comment: 20 page
Cyclotron Resonance in the Layered Perovskite Superconductor Sr2RuO4
We have measured the cyclotron masses in Sr2RuO4 through the observation of
periodic-orbit-resonances - a magnetic resonance technique closely related to
cyclotron resonance. We obtain values for the alpha, beta and gamma Fermi
surfaces of (4.33+/-0.05)me, (5.81+/-0.03)me and (9.71+/-0.11)me respectively.
The appreciable differences between these results and those obtained from de
Haas- van Alphen measurements are attributable to strong electron-electron
interactions in this system. Our findings appear to be consistent with
predictions for a strongly interacting Fermi liquid; indeed, semi-quantitative
agreement is obtained for the electron pockets beta and gamma.Comment: 4 pages + 3 figure
Effect of inorganic or organic copper fed without or with added sulfur and molybdenum on the performance, indicators of copper status, and hepatic mRNA in dairy cows
The effect of inorganic (INORG) or organic (ORG) Cu, fed without (â) or with (+) additional S and Mo on Cu status and performance was examined using 56 early lactation dairy cows in a 2 Ă 2 factorial study design. Supplementary Cu was added as either CuSO4 or BioplexCu (Alltech Inc., Nicholasville, KY) to provide an additional 10 mg of Cu/kg of dry matter (DM), with S added at 1.5 g/kg of DM and Mo at 6.8 mg/kg of DM to reduce Cu bioavailability. The basal ration was composed of corn and grass silages (2:1 respectively, DM basis) and straight feeds. Cows commenced the study at wk 7 of lactation and remained on treatment for 16 wk. An interaction existed between Cu source and added S and Mo on DM intake, with cows offered INORGâ Cu having an increased intake compared with those offered INORG+ or ORGâ Cu. Milk yield averaged 35.4 kg/d, and was 5% higher with milk fat content 6% lower in cows fed INORG compared with ORG Cu, but milk fat yield, energy-corrected milk yield, and milk protein content did not differ between treatments. A trend existed for cows to have a higher body weight gain when offered ORG compared with INORG Cu. Cows fed diets containing INORG Cu had a higher milk concentration of C17:0 and C18:3n-3 compared with those fed diets containing ORG Cu. Cows fed added S and Mo had a lower milk concentration of C17:0 and C18:0 compared with those that were not supplemented. No effect was observed of dietary treatment on plasma Cu concentration, which averaged 13.1 ”mol/L, except during wk 12 when cows receiving added S and Mo had a lower concentration. No effect was observed of Cu source on mean plasma Mo concentrations, but during wk 16 cows offered INORG Cu had a higher concentration than those offered ORG Cu. Hepatic Cu levels decreased by approximately 0.9 mg/kg of DM per day when fed additional S and Mo, but no effect of Cu source was observed. A trend existed for hepatic ATPase, Cu++ transporting, beta polypeptide (ATP7B) to be upregulated in cows when fed S and Mo along with ORG but not INORG Cu. In conclusion, the inclusion of an ORG compared with an INORG source of Cu reduced milk yield but increased milk fat concentration and body weight gain, with no effect on energy-corrected milk yield. Little effect was observed of dietary Cu supply on plasma mineral concentration, liver mRNA abundance, or milk fatty acid profile, whereas the addition of S and Mo reduced hepatic Cu concentrations
Classical field theory on Lie algebroids: Variational aspects
The variational formalism for classical field theories is extended to the
setting of Lie algebroids. Given a Lagrangian function we study the problem of
finding critical points of the action functional when we restrict the fields to
be morphisms of Lie algebroids. In addition to the standard case, our formalism
includes as particular examples the case of systems with symmetry (covariant
Euler-Poincare and Lagrange Poincare cases), Sigma models or Chern-Simons
theories.Comment: Talk deliverd at the 9th International Conference on Differential
Geometry and its Applications, Prague, September 2004. References adde
Decoherence suppression via environment preparation
To protect a quantum system from decoherence due to interaction with its
environment, we investigate the existence of initial states of the environment
allowing for decoherence-free evolution of the system. For models in which a
two-state system interacts with a dynamical environment, we prove that such
states exist if and only if the interaction and self-evolution Hamiltonians
share an eigenstate. If decoherence by state preparation is not possible, we
show that initial states minimizing decoherence result from a delicate
compromise between the environment and interaction dynamics.Comment: 4 pages, 2 figure
Nash Codes for Noisy Channels
This paper studies the stability of communication protocols that deal with
transmission errors. We consider a coordination game between an informed sender
and an uninformed decision maker, the receiver, who communicate over a noisy
channel. The sender's strategy, called a code, maps states of nature to
signals. The receiver's best response is to decode the received channel output
as the state with highest expected receiver payoff. Given this decoding, an
equilibrium or "Nash code" results if the sender encodes every state as
prescribed. We show two theorems that give sufficient conditions for Nash
codes. First, a receiver-optimal code defines a Nash code. A second, more
surprising observation holds for communication over a binary channel which is
used independently a number of times, a basic model of information
transmission: Under a minimal "monotonicity" requirement for breaking ties when
decoding, which holds generically, EVERY code is a Nash code.Comment: More general main Theorem 6.5 with better proof. New examples and
introductio
Vortex lattice structures of SrRuO
The vortex lattice structures of SrRuO for the odd parity
representations of the superconducting state are examined for the magnetic
field along the crystallographic directions. Particular emphasis is placed upon
the two dimensional representation which is believed to be relevant to this
material. It is shown that when the zero-field state breaks time reversal
symmetry, there must exist two superconducting transitions when there is a
finite field along a high symmetry direction in the basal plane. Also it is
shown that a square vortex lattice is expected when the field is along the
-axis. The orientation of the square lattice with respect to the underlying
ionic lattice yields information as to which Ru 4d orbitals are relevant to the
superconducting state.Comment: 5 pages, 2 figure
Mechanism of spin-triplet superconductivity in Sr2RuO4
The unique Fermi surfaces and their nesting properties of Sr2RuO4 are
considered. The existence of unconventional superconductivity is shown
microscopically, for the first time, from the magnetic interactions (due to
nesting) and the phonon-mediated interactions. The odd-parity superconductivity
is favored in the and sheets of the Fermi surface, and the
various superconductivities are possible in the sheet. There are a
number of possible odd-parity gaps, which include the gaps with nodes, the
breaking of time-reversal symmetry and .Comment: 4 pages, 3 figure
Fermi Surface, Surface States, and Surface Reconstruction in Sr2RuO4
The electronic structure of Sr2RuO4 is investigated by high angular
resolution ARPES at several incident photon energies. We address the
controversial issues of the Fermi surface (FS) topology and of the van Hove
singularity at the M point, showing that a surface state and the replica of the
primary FS due to (sqrt2 x sqrt2) surface reconstruction are responsible for
previous conflicting interpretations. The FS thus determined by ARPES is
consistent with the de Haas-van Alphen results, and it provides additional
information on the detailed shape of the alpha, beta and gamma sheets.Comment: Final version for Physical Review Letters. Revtex, 4 pages, 4
postscript pictures embedded in the tex
- âŠ