41,202 research outputs found
Phase transition in the Higgs model of scalar dyons
In the present paper we investigate the phase transition
"Coulomb--confinement" in the Higgs model of abelian scalar dyons -- particles
having both, electric and magnetic , charges. It is shown that by dual
symmetry this theory is equivalent to scalar fields with the effective squared
electric charge e^{*2}=e^2+g^2. But the Dirac relation distinguishes the
electric and magnetic charges of dyons. The following phase transition
couplings are obtained in the one--loop approximation:
\alpha_{crit}=e^2_{crit}/4\pi\approx 0.19,
\tilde\alpha_{crit}=g^2_{crit}/4\pi\approx 1.29 and \alpha^*_{crit}\approx
1.48.Comment: 16 pages, 2 figure
Theory of enhanced performance emerging in a sparsely-connected competitive population
We provide an analytic theory to explain Anghel et al.'s recent numerical
finding whereby a maximum in the global performance emerges for a
sparsely-connected competitive population [Phys. Rev. Lett. 92, 058701 (2004)].
We show that the effect originates in the highly-correlated dynamics of
strategy choice, and can be significantly enhanced using a simple modification
to the model.Comment: This revised version will appear in PRE as a Rapid Com
Lattice model theory of the equation of state covering the gas, liquid, and solid phases
The three stable states of matter and the corresponding phase transitions were obtained with a single model. Patterned after Lennard-Jones and Devonshires's theory, a simple cubic lattice model containing two fcc sublattices (alpha and beta) is adopted. The interatomic potential is taken to be the Lennard-Jones (6-12) potential. Employing the cluster variation method, the Weiss and the pair approximations on the lattice gas failed to give the correct phase diagrams. Hybrid approximations were devised to describe the lattice term in the free energy. A lattice vibration term corresponding to a free volume correction is included semi-phenomenologically. The combinations of the lattice part and the free volume part yield the three states and the proper phase diagrams. To determine the coexistence regions, the equalities of the pressure and Gibbs free energy per molecule of the coexisting phases were utilized. The ordered branch of the free energy gives rise to the solid phase while the disordered branch yields the gas and liquid phases. It is observed that the triple point and the critical point quantities, the phase diagrams and the coexistence regions plotted are in good agreement with the experimental values and graphs for argon
A deep level set method for image segmentation
This paper proposes a novel image segmentation approachthat integrates fully
convolutional networks (FCNs) with a level setmodel. Compared with a FCN, the
integrated method can incorporatesmoothing and prior information to achieve an
accurate segmentation.Furthermore, different than using the level set model as
a post-processingtool, we integrate it into the training phase to fine-tune the
FCN. Thisallows the use of unlabeled data during training in a
semi-supervisedsetting. Using two types of medical imaging data (liver CT and
left ven-tricle MRI data), we show that the integrated method achieves
goodperformance even when little training data is available, outperformingthe
FCN or the level set model alone
Wilson ratio of a Tomonaga-Luttinger liquid in a spin-1/2 Heisenberg ladder
Using micromechanical force magnetometry, we have measured the magnetization
of the strong-leg spin-1/2 ladder compound (CHN)CuBr at
temperatures down to 45 mK. Low-temperature magnetic susceptibility as a
function of field exhibits a maximum near the critical field H_c at which the
magnon gap vanishes, as expected for a gapped one-dimensional antiferromagnet.
Above H_c a clear minimum appears in the magnetization as a function of
temperature as predicted by theory. In this field region, the susceptibility in
conjunction with our specific heat data yields the Wilson ratio R_W. The result
supports the relation R_W=4K, where K is the Tomonaga-Luttinger-liquid
parameter
Discovery of Griffiths phase in itinerant magnetic semiconductor Fe_{1-x}Co_xS_2
Critical points that can be suppressed to zero temperature are interesting
because quantum fluctuations have been shown to dramatically alter electron gas
properties. Here, the metal formed by Co doping the paramagnetic insulator
FeS, FeCoS, is demonstrated to order ferromagnetically at
where we observe unusual transport, magnetic, and
thermodynamic properties. We show that this magnetic semiconductor undergoes a
percolative magnetic transition with distinct similarities to the Griffiths
phase, including singular behavior at and zero temperature.Comment: 10 pages, 4 figure
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