457 research outputs found
Roundabout relaxation: collective excitation requires a detour to equilibrium
Relaxation to equilibrium after strong and collective excitation is studied,
by using a Hamiltonian dynamical system of one dimensional XY model. After an
excitation of a domain of elements, the excitation is concentrated to fewer
elements, which are made farther away from equilibrium, and the excitation
intensity increases logarithmically with . Equilibrium is reached only after
taking this ``roundabout'' route, with the time for relaxation diverging
asymptotically as with .Comment: 4 pages, 5 figure
Ultrastable Optical Clock with Neutral Atoms in an Engineered Light Shift Trap
An ultrastable optical clock based on neutral atoms trapped in an optical
lattice is proposed. Complete control over the light shift is achieved by
employing the transition of
atoms as a "clock transition". Calculations of ac multipole polarizabilities
and dipole hyperpolarizabilities for the clock transition indicate that the
contribution of the higher-order light shifts can be reduced to less than 1
mHz, allowing for a projected accuracy of better than .Comment: 4 pages, 2 figures, accepted for publication in Phys. Rev. Let
Analytical evidence for the absence of spin glass transition on self-dual lattices
We show strong evidence for the absence of a finite-temperature spin glass
transition for the random-bond Ising model on self-dual lattices. The analysis
is performed by an application of duality relations, which enables us to derive
a precise but approximate location of the multicritical point on the Nishimori
line. This method can be systematically improved to presumably give the exact
result asymptotically. The duality analysis, in conjunction with the
relationship between the multicritical point and the spin glass transition
point for the symmetric distribution function of randomness, leads to the
conclusion of the absence of a finite-temperature spin glass transition for the
case of symmetric distribution. The result is applicable to the random bond
Ising model with or Gaussian distribution and the Potts gauge glass on
the square, triangular and hexagonal lattices as well as the random three-body
Ising model on the triangular and the Union-Jack lattices and the four
dimensional random plaquette gauge model. This conclusion is exact provided
that the replica method is valid and the asymptotic limit of the duality
analysis yields the exact location of the multicritical pointComment: 11 Pages, 4 figures, 1 table. submitted to J. Phys. A Math. Theo
Exact location of the multicritical point for finite-dimensional spin glasses: A conjecture
We present a conjecture on the exact location of the multicritical point in
the phase diagram of spin glass models in finite dimensions. By generalizing
our previous work, we combine duality and gauge symmetry for replicated random
systems to derive formulas which make it possible to understand all the
relevant available numerical results in a unified way. The method applies to
non-self-dual lattices as well as to self dual cases, in the former case of
which we derive a relation for a pair of values of multicritical points for
mutually dual lattices. The examples include the +-J and Gaussian Ising spin
glasses on the square, hexagonal and triangular lattices, the Potts and Z_q
models with chiral randomness on these lattices, and the three-dimensional +-J
Ising spin glass and the random plaquette gauge model.Comment: 27 pages, 3 figure
Free Boson Representation of
A representation of the quantum affine algebra of an
arbitrary level is constructed in the Fock module of eight boson fields.
This realization reduces the Wakimoto representation in the
limit. The analogues of the screening currents are also obtained. They commute
with the action of modulo total differences of some
fields.Comment: 12 pages, LaTeX, RIMS-920, YITP/K-101
Electronic inhomogeneity in EuO: Possibility of magnetic polaron states
We have observed the spatial inhomogeneity of the electronic structure of a
single-crystalline electron-doped EuO thin film with ferromagnetic ordering by
employing infrared magneto-optical imaging with synchrotron radiation. The
uniform paramagnetic electronic structure changes to a uniform ferromagnetic
structure via an inhomogeneous state with decreasing temperature and increasing
magnetic field slightly above the ordering temperature. One possibility of the
origin of the inhomogeneity is the appearance of magnetic polaron states.Comment: 4 pages, 3 figure
Dirac Electrons in Molecular Solids
Electrons in solids are characterized by the energy bands, which indicate
that electrons are considered to be "elementary particles" with specific
effective masses and g-factors reflecting features of each solid. There are
cases where these particles obey dispersion relationship similar to those of
Dirac electrons. Examples include graphite and bismuth both of which are known
for many years, together with graphene, a single layer of graphite, recently
addressed intensively after its realization. Another recent example is a
molecular solid, alpha-ET2I3, which is described by an equation similar to Weyl
equation with massless Dirac cones but the coordinate axis is tilted because of
the location of cones at off-symmetry points. Orbital susceptibility of such
Dirac electrons in graphite and bismuth has been known to have striking
features not present in ordinary band electrons but resulting from the
inter-band matrix elements of magnetic field. Results of theoretical studies on
not only orbital susceptibility but also Hall effect of such Dirac electrons in
molecular solids with tilting are introduced in this paper.Comment: 6 pages, 3 figure
Five-dimensional AGT Conjecture and the Deformed Virasoro Algebra
We study an analog of the AGT relation in five dimensions. We conjecture that
the instanton partition function of 5D N=1 pure SU(2) gauge theory coincides
with the inner product of the Gaiotto-like state in the deformed Virasoro
algebra. In four dimensional case, a relation between the Gaiotto construction
and the theory of Braverman and Etingof is also discussed.Comment: 12 pages, reference added, minor corrections (typos, notation
changes, etc
Heisenberg realization for U_q(sln) on the flag manifold
We give the Heisenberg realization for the quantum algebra , which
is written by the -difference operator on the flag manifold. We construct it
from the action of on the -symmetric algebra by the
Borel-Weil like approach. Our realization is applicable to the construction of
the free field realization for the [AOS].Comment: 10 pages, YITP/K-1016, plain TEX (some mistakes corrected and a
reference added
Multispin Ising spin glasses with ferromagnetic interactions
We consider the thermodynamics of an infinite-range Ising p-spin glass model
with an additional r-spin ferromagnetic interaction. For r=2 there is a
continuous transition to a ferromagnetic phase, while for r>2 the transition is
first order. We find both glassy and non-glassy ferromagnetic phases, with
replica symmetry breaking of both the one step and full varieties. We obtain
new results for the case where r=p>2, demonstrating the existence of a
non-glassy ferromagnetic phase, of significance to error-correcting codes.Comment: 16 pages, AMS LaTeX, 14 EPS figures; one minor correction to (42
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