23,680 research outputs found
Nonisomorphic Ordered Sets with Arbitrarily Many Ranks That Produce Equal Decks
We prove that for any there is a pair of
nonisomorphic ordered sets such that and have equal maximal
and minimal decks, equal neighborhood decks, and there are ranks such that for each the decks obtained by removing the points
of rank are equal. The ranks do not contain
extremal elements and at each of the other ranks there are elements whose
removal will produce isomorphic cards. Moreover, we show that such sets can be
constructed such that only for ranks and , both without extremal
elements, the decks obtained by removing the points of rank are not
equal.Comment: 30 pages, 6 figures, straight LaTe
Quiet Planting in the Locked Constraint Satisfaction Problems
We study the planted ensemble of locked constraint satisfaction problems. We
describe the connection between the random and planted ensembles. The use of
the cavity method is combined with arguments from reconstruction on trees and
first and second moment considerations; in particular the connection with the
reconstruction on trees appears to be crucial. Our main result is the location
of the hard region in the planted ensemble. In a part of that hard region
instances have with high probability a single satisfying assignment.Comment: 21 pages, revised versio
Some Ulam's reconstruction problems for quantum states
Provided a complete set of putative -body reductions of a multipartite
quantum state, can one determine if a joint state exists? We derive necessary
conditions for this to be true. In contrast to what is known as the quantum
marginal problem, we consider a setting where the labeling of the subsystems is
unknown. The problem can be seen in analogy to Ulam's reconstruction conjecture
in graph theory. The conjecture - still unsolved - claims that every graph on
at least three vertices can uniquely be reconstructed from the set of its
vertex-deleted subgraphs. When considering quantum states, we demonstrate that
the non-existence of joint states can, in some cases, already be inferred from
a set of marginals having the size of just more than half of the parties. We
apply these methods to graph states, where many constraints can be evaluated by
knowing the number of stabilizer elements of certain weights that appear in the
reductions. This perspective links with constraints that were derived in the
context of quantum error-correcting codes and polynomial invariants. Some of
these constraints can be interpreted as monogamy-like relations that limit the
correlations arising from quantum states. Lastly, we provide an answer to
Ulam's reconstruction problem for generic quantum states.Comment: 22 pages, 3 figures, v2: significantly revised final versio
Stability properties of the ENO method
We review the currently available stability properties of the ENO
reconstruction procedure, such as its monotonicity and non-oscillatory
properties, the sign property, upper bounds on cell interface jumps and a total
variation-type bound. We also outline how these properties can be applied to
derive stability and convergence of high-order accurate schemes for
conservation laws.Comment: To appear in Handbook of Numerical Methods for Hyperbolic Problem
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