1,221 research outputs found
Probing the helium-graphite interaction
Two separate lines of investigation have recently converged to produce a highly detailed picture of the
behavior of helium atoms physisorbed on graphite basal plane surfaces. Atomic beam scattering experiments
on single crystals have yielded accurate values for the binding energies of several· states for both (^4)He and (^3)He, as well as matrix elements of the largest Fourier component of the periodic part of the interaction potential.
From these data, a complete three-dimensional description of the potential has been constructed, and the
energy band structure of a helium atom moving in this potential calculated. At the same time, accurate
thermodynamic measurements were made on submonolayer helium films adsorbed on Grafoil. The binding
energy and low-coverage specific heat deduced from these measurements are in excellent agreement with
those calculated from the band structures
Quantum Weakly Nondeterministic Communication Complexity
We study the weakest model of quantum nondeterminism in which a classical
proof has to be checked with probability one by a quantum protocol. We show the
first separation between classical nondeterministic communication complexity
and this model of quantum nondeterministic communication complexity for a total
function. This separation is quadratic.Comment: 12 pages. v3: minor correction
Testing Linear-Invariant Non-Linear Properties
We consider the task of testing properties of Boolean functions that are
invariant under linear transformations of the Boolean cube. Previous work in
property testing, including the linearity test and the test for Reed-Muller
codes, has mostly focused on such tasks for linear properties. The one
exception is a test due to Green for "triangle freeness": a function
f:\cube^{n}\to\cube satisfies this property if do not all
equal 1, for any pair x,y\in\cube^{n}.
Here we extend this test to a more systematic study of testing for
linear-invariant non-linear properties. We consider properties that are
described by a single forbidden pattern (and its linear transformations), i.e.,
a property is given by points v_{1},...,v_{k}\in\cube^{k} and
f:\cube^{n}\to\cube satisfies the property that if for all linear maps
L:\cube^{k}\to\cube^{n} it is the case that do
not all equal 1. We show that this property is testable if the underlying
matroid specified by is a graphic matroid. This extends
Green's result to an infinite class of new properties.
Our techniques extend those of Green and in particular we establish a link
between the notion of "1-complexity linear systems" of Green and Tao, and
graphic matroids, to derive the results.Comment: This is the full version; conference version appeared in the
proceedings of STACS 200
Chromatic number, clique subdivisions, and the conjectures of Haj\'os and Erd\H{o}s-Fajtlowicz
For a graph , let denote its chromatic number and
denote the order of the largest clique subdivision in . Let H(n) be the
maximum of over all -vertex graphs . A famous
conjecture of Haj\'os from 1961 states that for every
graph . That is, for all positive integers . This
conjecture was disproved by Catlin in 1979. Erd\H{o}s and Fajtlowicz further
showed by considering a random graph that for some
absolute constant . In 1981 they conjectured that this bound is tight up
to a constant factor in that there is some absolute constant such that
for all -vertex graphs . In this
paper we prove the Erd\H{o}s-Fajtlowicz conjecture. The main ingredient in our
proof, which might be of independent interest, is an estimate on the order of
the largest clique subdivision which one can find in every graph on
vertices with independence number .Comment: 14 page
Asymptotic bounds for the sizes of constant dimension codes and an improved lower bound
We study asymptotic lower and upper bounds for the sizes of constant
dimension codes with respect to the subspace or injection distance, which is
used in random linear network coding. In this context we review known upper
bounds and show relations between them. A slightly improved version of the
so-called linkage construction is presented which is e.g. used to construct
constant dimension codes with subspace distance , dimension of the
codewords for all field sizes , and sufficiently large dimensions of the
ambient space, that exceed the MRD bound, for codes containing a lifted MRD
code, by Etzion and Silberstein.Comment: 30 pages, 3 table
The Erd\H{o}s-Ko-Rado theorem for twisted Grassmann graphs
We present a "modern" approach to the Erd\H{o}s-Ko-Rado theorem for
Q-polynomial distance-regular graphs and apply it to the twisted Grassmann
graphs discovered in 2005 by van Dam and Koolen.Comment: 5 page
From Quantum Query Complexity to State Complexity
State complexity of quantum finite automata is one of the interesting topics
in studying the power of quantum finite automata. It is therefore of importance
to develop general methods how to show state succinctness results for quantum
finite automata. One such method is presented and demonstrated in this paper.
In particular, we show that state succinctness results can be derived out of
query complexity results.Comment: Some typos in references were fixed. To appear in Gruska Festschrift
(2014). Comments are welcome. arXiv admin note: substantial text overlap with
arXiv:1402.7254, arXiv:1309.773
Determination of the Michel Parameters rho, xi, and delta in tau-Lepton Decays with tau --> rho nu Tags
Using the ARGUS detector at the storage ring DORIS II, we have
measured the Michel parameters , , and for
decays in -pair events produced at
center of mass energies in the region of the resonances. Using
as spin analyzing tags, we find , , , , and . In addition, we report
the combined ARGUS results on , , and using this work
und previous measurements.Comment: 10 pages, well formatted postscript can be found at
http://pktw06.phy.tu-dresden.de/iktp/pub/desy97-194.p
Centerscope
Centerscope, formerly Scope, was published by the Boston University Medical Center "to communicate the concern of the Medical Center for the development and maintenance of improved health care in contemporary society.
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