411 research outputs found
Critical interfaces and duality in the Ashkin Teller model
We report on the numerical measures on different spin interfaces and FK
cluster boundaries in the Askhin-Teller (AT) model. For a general point on the
AT critical line, we find that the fractal dimension of a generic spin cluster
interface can take one of four different possible values. In particular we
found spin interfaces whose fractal dimension is d_f=3/2 all along the critical
line. Further, the fractal dimension of the boundaries of FK clusters were
found to satisfy all along the AT critical line a duality relation with the
fractal dimension of their outer boundaries. This result provides a clear
numerical evidence that such duality, which is well known in the case of the
O(n) model, exists in a extended CFT.Comment: 5 pages, 4 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
Numerical study on Schramm-Loewner Evolution in nonminimal conformal field theories
The Schramm-Loewner evolution (SLE) is a powerful tool to describe fractal
interfaces in 2D critical statistical systems. Yet the application of SLE is
well established for statistical systems described by quantum field theories
satisfying only conformal invariance, the so called minimal conformal field
theories (CFTs). We consider interfaces in Z(N) spin models at their self-dual
critical point for N=4 and N=5. These lattice models are described in the
continuum limit by non-minimal CFTs where the role of a Z_N symmetry, in
addition to the conformal one, should be taken into account. We provide
numerical results on the fractal dimension of the interfaces which are SLE
candidates for non-minimal CFTs. Our results are in excellent agreement with
some recent theoretical predictions.Comment: 4 pages, 2 figures, v2: typos corrected, 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
Sepsis target validation for repurposing and combining complement and immune checkpoint inhibition therapeutics
Introduction: Sepsis is a disease that occurs due to an adverse immune response to infection by bacteria, viruses and fungi and is the leading pathway to death by infection. The hallmarks for maladapted immune reactions in severe sepsis, which contribute to multiple organ failure and death, are bookended by the exacerbated activation of the complement system to protracted T-cell dysfunction states orchestrated by immune checkpoint control. Despite major advances in our understanding of the condition, there remains to be either a definitive test or an effective therapeutic intervention.
Areas covered: The authors consider a combinational drug therapy approach using new biologics, and mathematical modeling for predicting patient responses, in targeting innate and adaptive immune mediators underlying sepsis. Special consideration is given for emerging complement and immune checkpoint inhibitors that may be repurposed for sepsis treatment.
Expert opinion: In order to overcome the challenges inherent to finding new therapies for the complex dysregulated host response to infection that drives sepsis, it is necessary to move away from monotherapy and promote precision for personalized combinatory therapies. Notably, combinatory therapy should be guided by predictive systems models of the immune-metabolic characteristics of an individual’s disease progression
Non-compact local excitations in spin glasses
We study numerically the local low-energy excitations in the 3-d
Edwards-Anderson model for spin glasses. Given the ground state, we determine
the lowest-lying connected cluster of flipped spins with a fixed volume
containing one given spin. These excitations are not compact, having a fractal
dimension close to two, suggesting an analogy with lattice animals. Also, their
energy does not grow with their size; the associated exponent is slightly
negative whereas the one for compact clusters is positive. These findings call
for a modification of the basic hypotheses underlying the droplet model.Comment: 7 pages, LaTex, discussion on stability clarifie
Nonequilibrium critical dynamics of the bi-dimensional Ising model
The Ising model is a simple frustrated spin model, where the exchange
couplings independently take the discrete value with probability and
with probability . It is especially appealing due to its connection
to quantum error correcting codes. Here, we investigate the nonequilibrium
critical behavior of the bi-dimensional Ising model, after a quench
from different initial conditions to a critical point on the
paramagnetic-ferromagnetic (PF) transition line, especially, above, below and
at the multicritical Nishimori point (NP). The dynamical critical exponent
seems to exhibit non-universal behavior for quenches above and below the
NP, which is identified as a pre-asymptotic feature due to the repulsive fixed
point at the NP. Whereas, for a quench directly to the NP, the dynamics reaches
the asymptotic regime with . We also consider the
geometrical spin clusters (of like spin signs) during the critical dynamics.
Each universality class on the PF line is uniquely characterized by the
stochastic Loewner evolution (SLE) with corresponding parameter .
Moreover, for the critical quenches from the paramagnetic phase, the model,
irrespective of the frustration, exhibits an emergent critical percolation
topology at the large length scales.Comment: 26 pages, 10 figure
Weak Randomness for large q-State Potts models in Two Dimensions
We have studied the effect of weak randomness on q-state Potts models for q >
4 by measuring the central charges of these models using transfer matrix
methods. We obtain a set of new values for the central charges and then show
that some of these values are related to one another by a factorization law.Comment: 8 pages, Latex, no figure
Wang-Landau study of the random bond square Ising model with nearest- and next-nearest-neighbor interactions
We report results of a Wang-Landau study of the random bond square Ising
model with nearest- () and next-nearest-neighbor ()
antiferromagnetic interactions. We consider the case for
which the competitive nature of interactions produces a sublattice ordering
known as superantiferromagnetism and the pure system undergoes a second-order
transition with a positive specific heat exponent . For a particular
disorder strength we study the effects of bond randomness and we find that,
while the critical exponents of the correlation length , magnetization
, and magnetic susceptibility increase when compared to the
pure model, the ratios and remain unchanged. Thus, the
disordered system obeys weak universality and hyperscaling similarly to other
two-dimensional disordered systems. However, the specific heat exhibits an
unusually strong saturating behavior which distinguishes the present case of
competing interactions from other two-dimensional random bond systems studied
previously.Comment: 9 pages, 3 figures, version as accepted for publicatio
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