Markov random fields are often used to model high dimensional distributions in a number of applied areas. A number of recent papers have studied the problem of reconstructing a dependency graph of bounded degree from independent samples from the Markov random field. These results require observing samples of the distribution at all nodes of the graph. It was heuristically recognized that the pr...

A spectrahedron is the feasible region of a semideenite program. In this paper, we investigate the conditions under which a given spectrahedron is polyhedral. Characterizations of those matrix maps for which the associated spectrahedron is polyhedral are derived. It is then shown that, while polyhedrality is CoNP-Hard to detect in general, under certain assumptions, it can be recognized in rand...

We investigated the role of cAMP-responsive element-binding protein (CREB) in genetic predisposition to anxiety and alcohol-drinking behaviors using alcohol-preferring (P) and -nonpreferring (NP) rats. The levels of CREB, phosphorylated CREB, and neuropeptide Y (NPY) were innately lower in the central amygdala (CeA) and medial amygdala (MeA), but not in the basolateral amygdala (BLA), of P rats...

The quadruple system PG 1115+080 is the second gravitational lens with a reported measurement of the Hubble constant. In addition to the primary lens, three nearby galaxies are believed to contribute significantly to the lensing potential. In this letter we report accurate redshifts for all four galaxies and show that they belong to a single group at zd = 0.311. This group has very similar prop...

Department of Computer Science, The University of Liverpool, Chadwick Building, Peach Street, Liverpool, L69 7ZF, UK, tel: +44-151-794 3706, fax: +44-151-794 3715, email: [email protected] SAP AG Entw. HR HRMS Netherlands, PO Box 1461, D-69190 Walldorf, Germany, tel: +49-622776 47 45, fax: +49-6227-77 47 45, email: [email protected] Dipartimento di Informatica, Universita' degli Studi di ...

Let X rv Np(O, E), the p-variate normal distribution with mean °and positive definite covariance matrix .E. Anderson (1955) showed that if .E2 .E1 is positive semidefinite then PEl (C) 2: P E2(C) for every centrally symmetric (-C = convex set C ~ RP. Fefferman, Jodeit, and Perlman (1972) extended this result to elliptically contoured distributions. In the present paper similar multivariate f f"...

Given an n-vertex graph G and a function f : V (G)→ {0, . . . , n−1}, an f -factor is a subgraph H of G such that degH(v) = f(v) for every vertex v ∈ V (G); we say that H is a connected f -factor if, in addition, the subgraph H is connected. A classical result of Tutte (1954) is the polynomial time algorithm to check whether a given graph has a specified f -factor. However, checking for the pre...

We consider inapproximability issue for the correlation clustering problem introduced by Bansal, Blum and Chawla [1]. Given a graph G = (V,E) where each edge is labeled either ”+” (similar) or ”−” (dissimilar), correlation clustering seeks to partition the vertices into clusters so that the number of pairs correctly (resp. incorrectly) classified with respected to the labels is maximized (resp....

Björklund and Husfeldt developed a randomized polynomial time algorithm to solve the shortest two disjoint paths problem. Their algorithm is based on computation of permanents modulo 4 and the isolation lemma. In this paper, we consider the following generalization of the shortest two disjoint paths problem, and develop a similar algebraic algorithm. The shortest perfect (A + B)-path packing pr...

We consider the problem of approximating the partition function of the hard-core model on planar graphs of degree at most 4. We show that when the activity λ is sufficiently large, there is no fully polynomial randomised approximation scheme for evaluating the partition function unless NP = RP. The result extends to a nearby region of the parameter space in a more general two-state spin system ...