468 research outputs found
Gauge theory for mixed -spin glasses
Physical quantities in the mixed -spin glasses are evaluated with
Nishimori's gauge theory and several variance inequalities. The -symmetry breaking and the replica-symmetry breaking are studied in finite
and infinite dimensions. Obtained bounds on the expectation of the square of
the magnetization and spontaneous magnetization enable us to clarify properties
of paramagnetic and spin glass phases. It is proven that variances of
ferromagnetic and spin glass order parameters vanish on the Nishimori line in
the infinite volume limit. These results imply the self-averaging of these
order parameters on the Nishimori line. The self-averaging of the spin glass
order parameter rigorously justifies already argued absence of replica-symmetry
breaking on the Nishimori line.Comment: 13 page
Deformation of a renormalization-group equation applied to infinite-order phase transitions
By adding a linear term to a renormalization-group equation in a system
exhibiting infinite-order phase transitions, asymptotic behavior of running
coupling constants is derived in an algebraic manner. A benefit of this method
is presented explicitly using several examples.Comment: 6 pages, 5 figures, revtex4, typo corrected, references adde
Phase diagram of a 1 dimensional spin-orbital model
We study a 1 dimensional spin-orbital model using both analytical and
numerical methods. Renormalization group calculations are performed in the
vicinity of a special integrable point in the phase diagram with SU(4)
symmetry. These indicate the existence of a gapless phase in an extended region
of the phase diagram, missed in previous studies. This phase is SU(4) invariant
at low energies apart from the presence of different velocities for spin and
orbital degrees of freedom. The phase transition into a gapped dimerized phase
is in a generalized Kosterlitz-Thouless universality class. The phase diagram
of this model is sketched using the density matrix renormalization group
technique.Comment: 11 pages, 5 figures, new references adde
Antiferromagnetic S=1/2 Heisenberg Chain and the Two-flavor Massless Schwinger Model
An antiferromagnetic S=1/2 Heisenberg chain is mapped to the two-flavor
massless Schwinger model at \theta=\pi. The electromagnetic coupling constant
and velocity of light in the Schwinger model are determined in terms of the
Heisenberg coupling and lattice spacing in the spin chain system.Comment: 3 pages. LaTex2
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