1,008 research outputs found
Aging effects and dynamic scaling in the 3d Edwards-Anderson spin glasses: a comparison with experiments
We present a detailed study of the scaling behavior of correlations functions
and AC susceptibility relaxations in the aging regime in three dimensional spin
glasses. The agreement between simulations and experiments is excellent
confirming the validity of the full aging scenario with logarithmic corrections
which manifests as weak sub-aging effects.Comment: 6 pages, 6 figures. Previously appeared as a part of cond-mat/000554
Further evidence of the absence of Replica Symmetry Breaking in Random Bond Potts Models
In this short note, we present supporting evidence for the replica symmetric
approach to the random bond q-state Potts models. The evidence is statistically
strong enough to reject the applicability of the Parisi replica symmetry
breaking scheme to this class of models. The test we use is a generalization of
one formerly proposed by Dotsenko et al. and consists in measuring scaling laws
of disordered-averaged moments of the spin-spin correlation functions.
Numerical results, obtained via Monte Carlo simulations for several values of
q, are shown to be in fair agreement with the replica symmetric values computed
by using perturbative CFT for the second and third moments of the q=3 model.
RSB effects, which should increase in strength with moment, are unobserved.Comment: 7 pages, some minor modifications (mainly misprints). To Appear in
Europhysics Letter
Multicritical points for the spin glass models on hierarchical lattices
The locations of multicritical points on many hierarchical lattices are
numerically investigated by the renormalization group analysis. The results are
compared with an analytical conjecture derived by using the duality, the gauge
symmetry and the replica method. We find that the conjecture does not give the
exact answer but leads to locations slightly away from the numerically reliable
data. We propose an improved conjecture to give more precise predictions of the
multicritical points than the conventional one. This improvement is inspired by
a new point of view coming from renormalization group and succeeds in deriving
very consistent answers with many numerical data.Comment: 11 pages, 9 figures, 7 tables This is the published versio
Critical interfaces of the Ashkin-Teller model at the parafermionic point
We present an extensive study of interfaces defined in the Z_4 spin lattice
representation of the Ashkin-Teller (AT) model. In particular, we numerically
compute the fractal dimensions of boundary and bulk interfaces at the
Fateev-Zamolodchikov point. This point is a special point on the self-dual
critical line of the AT model and it is described in the continuum limit by the
Z_4 parafermionic theory. Extending on previous analytical and numerical
studies [10,12], we point out the existence of three different values of
fractal dimensions which characterize different kind of interfaces. We argue
that this result may be related to the classification of primary operators of
the parafermionic algebra. The scenario emerging from the studies presented
here is expected to unveil general aspects of geometrical objects of critical
AT model, and thus of c=1 critical theories in general.Comment: 15 pages, 3 figure
Scale Invariance and Self-averaging in disordered systems
In a previous paper we found that in the random field Ising model at zero
temperature in three dimensions the correlation length is not self-averaging
near the critical point and that the violation of self-averaging is maximal.
This is due to the formation of bound states in the underlying field theory. We
present a similar study for the case of disordered Potts and Ising ferromagnets
in two dimensions near the critical temperature. In the random Potts model the
correlation length is not self-averaging near the critical temperature but the
violation of self-averaging is weaker than in the random field case. In the
random Ising model we find still weaker violations of self-averaging and we
cannot rule out the possibility of the restoration of self-averaging in the
infinite volume limit.Comment: 7 pages, 4 ps figure
Random Bond Potts Model: the Test of the Replica Symmetry Breaking
Averaged spin-spin correlation function squared
is calculated for the ferromagnetic
random bond Potts model. The technique being used is the renormalization group
plus conformal field theory. The results are of the - expansion type
fixed point calculation, being the deviation of the central charge
(or the number of components) of the Potts model from the Ising model value.
Calculations are done both for the replica symmetric and the replica symmetry
broken fixed points. The results obtained allow for the numerical simulation
tests to decide between the two different criticalities of the random bond
Potts model.Comment: 50 pages, Latex, 2 eps figure
Identifying Heating Technologies suitable for Historic Churches, Taking into Account Heating Strategy and Conservation through Pairwise Analysis
As a result of difficulty meeting energy efficiency through fabric alteration, historic churches must focus on heating systems and operational strategy as key to reducing carbon emissions. Strategies can be defined as local or central heating. Local heating strives to heat occupants, while central heating aims to heat the building fabric and therefore the occupants. Each strategy requires a different approach to control and technology in response to priorities such as conservation, comfort and cost. This paper reviews current and emerging technologies in the context of church heating. The fuel source, heat generation technology and heat emitter are arranged in a matrix, with pairwise analysis undertaken to create weightings for each assessment criteria. The process of constructing the matrix and undertaking pairwise analysis using personas is discussed. The result is a ranking of fuels and technologies appropriate to the main priorities and individual preferences. Some desirable technologies are inherently more damaging to historic church environments due to invasive installation. These technologies score poorly when the aim is fabric preservation. Greener fuels, like biomass, may rank lower than fossil fuels, due in part to operational differences
Replica symmetry breaking transition of the weakly anisotropic Heisenberg spin glass in magnetic fields
The spin and the chirality orderings of the three-dimensional Heisenberg spin
glass with the weak random anisotropy are studied under applied magnetic fields
by equilibrium Monte Carlo simulations. A replica symmetry breaking transition
occurs in the chiral sector accompanied by the simultaneous spin-glass order.
The ordering behavior differs significantly from that of the Ising SG, despite
the similarity in the global symmetry. Our observation is consistent with the
spin-chirality decoupling-recoupling scenario of a spin-glass transition.Comment: 4 pages, 4 figure
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