2,239 research outputs found
Stability of a two-sublattice spin-glass model
We study the stability of the replica-symmetric solution of a two-sublattice
infinite-range spin-glass model, which can describe the transition from
antiferromagnetic to spin glass state. The eigenvalues associated with
replica-symmetric perturbations are in general complex. The natural
generalization of the usual stability condition is to require the real part of
these eigenvalues to be positive. The necessary and sufficient conditions for
all the roots of the secular equation to have positive real parts is given by
the Hurwitz criterion. The generalized stability condition allows a consistent
analysis of the phase diagram within the replica-symmetric approximation.Comment: 21 pages, 5 figure
Observations of gravity waves in the mesosphere with the MU radar
Wind motions were observed at 60 to 90 km altitudes with the MU radar during daylight hours (0800 to 1600 LT) from 13 to 31 October 1986. Quasi-monochromatic gravity waves were evident on 16 of the 19 days of observations. They were characterized by typical vertical wavelength of 5 to 15 km and intrinsic periods centered at about 9 hours. The propagation direction of the gravity waves, determined by the gravity wave dispersion relation, was mostly equatorward. The vertical wave number spectra of the horizontal components of the mesoscale wind fluctuations are explained well by saturated gravity wave theory. The frequency spectrum of vertical wind component has a slope of + 1/3, while the oblique spectra have a slope of -5/3 up to 4 x 10(-3) (c/s); these agree fairly well with model gravity wave spectra. Doppler shift effects on the frequency spectra are recognized at higher frequencies. Upward flux was determined of horizontal momentum flux induced by waves with periods from 10 min to 8 hours, and westward and northward body forces of 5.1 and 4.0 m/s/day, were estimated respectively
Random-energy model in random fields
The random-energy model is studied in the presence of random fields.
The problem is solved exactly both in the microcanonical ensemble, without
recourse to the replica method, and in the canonical ensemble using the replica
formalism. The phase diagrams for bimodal and Gaussian random fields are
investigated in detail. In contrast to the Gaussian case, the bimodal random
field may lead to a tricritical point and a first-order transition. An
interesting feature of the phase diagram is the possibility of a first-order
transition from paramagnetic to mixed phase.Comment: 18 pages, 5 figures (included
Amelioration of normothermic canine liver ischemia with prostacyclin.
A model of hepatic ischemia was developed in dogs using a pump-driven splanchnic-to-jugular vein bypass during crossclamping of the portal triad. An LD50 was established with three hours of ischemia. PGI2 given for one hour before the ischemic insult ameliorated the ischemic injury and increased survival
Antiferromagnetic spherical spin-glass model
We study the thermodynamic properties and the phase diagrams of a multi-spin
antiferromagnetic spherical spin-glass model using the replica method. It is a
two-sublattice version of the ferromagnetic spherical p-spin glass model. We
consider both the replica-symmetric and the one-step replica-symmetry-breaking
solutions, the latter being the most general solution for this model. We find
paramagnetic, spin-glass, antiferromagnetic and mixed or glassy
antiferromagnetic phases. The phase transitions are always of second order in
the thermodynamic sense, but the spin-glass order parameter may undergo a
discontinuous change.Comment: 12 pages, 6 figure
An FFAG Transport Line for the PAMELA Project
The PAMELA project to design an accelerator for
hadron therapy using non-scaling Fixed Field Alternating
Gradient (NS-FFAG) magnets requires a transport line
and gantry to take the beam to the patient. The NS-FFAG
principle offers the possibility of a gantry much smaller,
lighter and cheaper than conventional designs, with the
added ability to accept a wide range of fast changing
energies. This paper will build on previous work to
investigate a transport line which could be used for the
PAMELA project. The design is presented along with a
study and optimisation of its acceptance
Relationships between a roller and a dynamic pressure distribution in circular hydraulic jumps
We investigated numerically the relation between a roller and the pressure
distribution to clarify the dynamics of the roller in circular hydraulic jumps.
We found that a roller which characterizes a type II jump is associated with
two high pressure regions after the jump, while a type I jump (without the
roller) is associated with only one high pressure region. Our numerical results
show that building up an appropriate pressure field is essential for a roller.Comment: 10 pages, 7 PS files. To appear in PR
Note on Triangle Anomalies and Assignment of Singlet in 331-like Model
It is pointed out that in the like model which uses both fundamental
and complex conjugate representations for an assignment of the representations
to the left-handed quarks and the scalar representation to their corresponding
right-handed counterparts, the nature of the scalar should be taken into
account in order to make the fermion triangle anomalies in the theory
anomaly-free, i.e. renormalizable in a sense with no anomalies, even after the
spontaneous symmetry breaking.Comment: 8 page no figures, acknowledgments adde
- …