908 research outputs found
Probing the neutral edge modes in transport across a point contact via thermal effects in the Read-Rezayi non-abelian quantum Hall states
Non-abelian quantum Hall states are characterized by the simultaneous
appearance of charge and neutral gapless edge modes, with the structure of the
latter being intricately related to the existence of bulk quasi-particle
excitations obeying non-abelian statistics. In general, it is hard to probe the
neutral modes in charge transport measurements and a thermal transport
measurement seems to be inevitable. Here we propose a setup which can get
around this problem by having two point contacts in series separated by a
distance set by the thermal equilibration length of the charge mode. We show
that by using the first point contact as a heating device, the excess charge
noise measured at the second point contact carries a non-trivial signature of
the presence of the neutral mode hence leading to its indirect detection. We
also obtain explicit expressions for the thermal conductance and corresponding
Lorentz number for transport across a quantum point contact between two edges
held at different temperatures and chemical potentials
Large Deviations of the Smallest Eigenvalue of the Wishart-Laguerre Ensemble
We consider the large deviations of the smallest eigenvalue of the
Wishart-Laguerre Ensemble. Using the Coulomb gas picture we obtain rate
functions for the large fluctuations to the left and the right of the hard
edge. Our findings are compared with known exact results for finding
good agreement. We also consider the case of almost square matrices finding new
universal rate functions describing large fluctuations.Comment: 4 pages, 2 figure
Coulomb blockade as a probe for non-Abelian statistics in Read-Rezayi states
We consider a quantum dot in the regime of the quantum Hall effect,
particularly in Laughlin states and non-Abelian Read-Rezayi states. We find the
location of the Coulomb blockade peaks in the conductance as a function of the
area of the dot and the magnetic field. When the magnetic field is fixed and
the area of the dot is varied, the peaks are equally spaced for the Laughlin
states. In contrast, non-Abelian statistics is reflected in modulations of the
spacing which depend on the magnetic field.Comment: Published versio
Experimental signatures of non-Abelian statistics in clustered quantum Hall states
We discuss transport experiments for various non-Abelian quantum Hall states,
including the Read-Rezayi series and a paired spin singlet state. We analyze
the signatures of the unique characters of these states on Coulomb blockaded
transport through large quantum dots. We show that the non-Abelian nature of
the states manifests itself through modulations in the spacings between Coulomb
blockade peaks as a function of the area of the dot. Even though the current
flows only along the edge, these modulations vary with the number of quasiholes
that are localized in the bulk of the dot. We discuss the effect of relaxation
of edge states on the predicted Coulomb blockade patterns, and show that it may
suppress the dependence on the number of bulk quasiholes. We predict the form
of the lowest order interference term in a Fabry-Perot interferometer for the
spin singlet state. The result indicates that this interference term is
suppressed for certain values of the quantum numbers of the collective state of
the bulk quasiholes, in agreement with previous findings for other clustered
states belonging to the Read-Rezayi series.Comment: 19 pages, 4 figures, 2 tables. Published versio
Lack of Ultrametricity in the Low-Temperature phase of 3D Ising Spin Glasses
We study the low-temperature spin-glass phases of the Sherrington-Kirkpatrick
(SK) model and of the 3-dimensional short range Ising spin glass (3dISG). For
the SK model, evidence for ultrametricity becomes clearer as the system size
increases, while for the short-range case our results indicate the opposite,
i.e. lack of ultrametricity. Our results are obtained by a recently proposed
method that uses clustering to focus on the relevant parts of phase space and
reduce finite size effects. Evidence that the mean field solution does not
apply in detail to the 3dISG is also found by another method which does not
rely on clustering
Modeling cancer metabolism on a genome scale
Cancer cells have fundamentally altered cellular metabolism that is associated with their tumorigenicity and malignancy. In addition to the widely studied Warburg effect, several new key metabolic alterations in cancer have been established over the last decade, leading to the recognition that altered tumor metabolism is one of the hallmarks of cancer. Deciphering the full scope and functional implications of the dysregulated metabolism in cancer requires both the advancement of a variety of omics measurements and the advancement of computational approaches for the analysis and contextualization of the accumulated data. Encouragingly, while the metabolic network is highly interconnected and complex, it is at the same time probably the best characterized cellular network. Following, this review discusses the challenges that genome‐scale modeling of cancer metabolism has been facing. We survey several recent studies demonstrating the first strides that have been done, testifying to the value of this approach in portraying a network‐level view of the cancer metabolism and in identifying novel drug targets and biomarkers. Finally, we outline a few new steps that may further advance this field
THE COMPETITIVE DYNAMICS OF WEB SITES
The phenomenon of electronic commerce has led to a proliferation of web sites competing for the attention and resources of millions of consumers. As has been recently shown, the resulting dynamics is such that a few sites command most of the traffic in the web, a signature of a winner-take-all market[1].In order to explore the effects of competition among web sites and to determine how they affect the nature of markets, we present a dynamical model of web site growth and competition, which takes into account both the evolution of the probabilities that a person visits sites as well as the existence of links between sites.We show that under general conditions, as the competition between sites increases, the model exhibits a sudden transition from a regime in which many sites thrive simultaneously, to a "winner take all market" in which a few sites grab almost all the users, while most other sites go nearly extinct. This transition is similar to what in ecology is called the Principle of Competitive Exclusion.Furthermore, we study the effect of site linkage on the number of visitors to both competitive and cooperative sites, as well as the implications of our results for linking strategies as practiced on the web. Common link structures found on the web, such as web rings, are also analyzed.Finally, we show web usage data that motivates our work and places the different behaviors in context.
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