1,518 research outputs found
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
Gauge Theory for Quantum Spin Glasses
The gauge theory for random spin systems is extended to quantum spin glasses
to derive a number of exact and/or rigorous results. The transverse Ising model
and the quantum gauge glass are shown to be gauge invariant. For these models,
an identity is proved that the expectation value of the gauge invariant
operator in the ferromagnetic limit is equal to the one in the classical
equilibrium state on the Nishimori line. As a result, a set of inequalities for
the correlation function are proved, which restrict the location of the ordered
phase. It is also proved that there is no long-range order in the
two-dimensional quantum gauge glass in the ground state. The phase diagram for
the quantum XY Mattis model is determined.Comment: 15 pages, 2 figure
A New Method to Calculate the Spin-Glass Order Parameter of the Two-Dimensional +/-J Ising Model
A new method to numerically calculate the th moment of the spin overlap of
the two-dimensional Ising model is developed using the identity derived
by one of the authors (HK) several years ago. By using the method, the th
moment of the spin overlap can be calculated as a simple average of the th
moment of the total spins with a modified bond probability distribution. The
values of the Binder parameter etc have been extensively calculated with the
linear size, , up to L=23. The accuracy of the calculations in the present
method is similar to that in the conventional transfer matrix method with about
bond samples. The simple scaling plots of the Binder parameter and the
spin-glass susceptibility indicate the existence of a finite-temperature
spin-glass phase transition. We find, however, that the estimation of is strongly affected by the corrections to scaling within the present data
(). Thus, there still remains the possibility that ,
contrary to the recent results which suggest the existence of a
finite-temperature spin-glass phase transition.Comment: 10 pages,8 figures: final version to appear in J. Phys.
Aging Relation for Ising Spin Glasses
We derive a rigorous dynamical relation on aging phenomena -- the aging
relation -- for Ising spin glasses using the method of gauge transformation.
The waiting-time dependence of the auto-correlation function in the
zero-field-cooling process is equivalent with that in the field-quenching
process. There is no aging on the Nishimori line; this reveals arguments for
dynamical properties of the Griffiths phase and the mixed phase. The present
method can be applied to other gauge-symmetric models such as the XY gauge
glass.Comment: 9 pages, RevTeX, 2 postscript figure
Non-equilibrium Relations for Spin Glasses with Gauge Symmetry
We study the applications of non-equilibrium relations such as the Jarzynski
equality and fluctuation theorem to spin glasses with gauge symmetry. It is
shown that the exponentiated free-energy difference appearing in the Jarzynski
equality reduces to a simple analytic function written explicitly in terms of
the initial and final temperatures if the temperature satisfies a certain
condition related to gauge symmetry. This result is used to derive a lower
bound on the work done during the non-equilibrium process of temperature
change. We also prove identities relating equilibrium and non-equilibrium
quantities. These identities suggest a method to evaluate equilibrium
quantities from non-equilibrium computations, which may be useful to avoid the
problem of slow relaxation in spin glasses.Comment: 8 pages, 2 figures, submitted to JPS
Dynamical Gauge Theory for the XY Gauge Glass Model
Dynamical systems of the gauge glass are investigated by the method of the
gauge transformation.Both stochastic and deterministic dynamics are treated.
Several exact relations are derived among dynamical quantities such as
equilibrium and nonequilibrium auto-correlation functions, relaxation functions
of order parameter and internal energy. They provide physical properties in
terms of dynamics in the SG phase, a possible mixed phase and the Griffiths
phase, the multicritical dynamics and the aging phenomenon. We also have a
plausible argument for the absence of re-entrant transition in two or higher
dimensions.Comment: 3 figure
Tcnq-based Porous Coordination Polymers Synthesis and Sorption Properties Study in Magnetic Field
Porous coordination polymers (PCPs) were synthesized with used TCNQ anion that acts as cross linker connecting and bipyridine to form a 3D framework. In these study, we use zinc and manganese metal ion as centre of complex coordination. Green crystal of Zn(TCNQ-TCNQ)bpy.1.5 benzene and Mn(TCNQ-TCNQ)bpy.1.5 benzene was successfully synthesized in no under magnetic field (0T) and under magnetic field 6T. XRD patterns of Zn(TCNQ-TCNQ)bpy.1.5 benzene 0T and 6T shown not significant different pattern that indicate no different crytal formed. XRD patterns of Mn(TCNQ-TCNQ)bpy.1.5 benzene also shown not significant different but we found five different intensity ratio peaks that possibility it was a little bit changing of crystal structure. To investigate the pores properties, adsorption isotherm was performe for oxygen gas in 77 K and the guest of benzene were removed at 413 K for 3 hours under low pressure. Zn(TCNQ-TCNQ)bpy}1.5benzene 0T and 6T oxygen adsorption isotherms shows the unique sorption isotherms by gate pressure profile. On other hand, Mn(TCNQ-TCNQ)bpy}1.5 benzene 0T and 6T shows type 1 adsorption isotherms for micropores materials. Adsorption isotherm was also determined in magnetic field 6T for all crystal, and shows shift of gate pressure for Zn compounds and enhance the amount of oxygen adsorbed for all kind of compounds
Phase Diagram of Lattice-Spin System RbCoBr
We study the lattice-spin model of RbCoBr which is proposed by Shirahata
and Nakamura, by mean field approximation. This model is an Ising spin system
on a distorted triangular lattice. There are two kinds of frustrated variables,
that is, the lattice and spin. We obtain a phase diagram of which phase
boundary is drawn continuously in a whole region. Intermediate phases that
include a partial disordered state appear. The model has the first-order phase
transitions in addition to the second-order phase transitions. We find a
three-sublattice ferrimagnetic state in the phase diagram. The three-sublattice
ferrimagnetic state does not appear when the lattice is not distorted.Comment: 5 pages, 4 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn.
Vol.75 (2006) No.
Laboratory Measurement of the Pure Rotational Transitions of the HCNH+ and its Isotopic Species
The pure rotational transitions of the protonated hydrogen cyanide ion,
HCNH+, and its isotopic species, HCND+ and DCND+, were measured in the 107 -
482 GHz region with a source modulated microwave spectrometer. The ions were
generated in the cell with a magnetically confined dc-glow discharge of HCN
and/or DCN. The rotational constant B0 and the centrifugal distortion constant
D0 for each ion were precisely determined by a least-squares fitting to the
observed spectral lines. The observed rotational transition frequencies by
laboratory spectroscopy and the predicted ones are accurate in about 30 to 40
kHz and are useful as rest frequencies for astronomical searches of HCNH+ and
HCND+.Comment: 14 pages in TeX, 1 figures in JPE
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