6,057 research outputs found
Adiabatic Cooling with Non-Abelian Anyons
We show in this Letter that the ground state degeneracy associated with the
presence of non-Abelian anyons can be probed by using an adiabatic cooling
process based on the non-Abelian entropy. In particular, we show that when the
number of such anyons is increased adiabatically at sufficiently low
temperatures, the non-Abelian liquid undergoes cooling, whereas heating occurs
in the Abelian case. Estimates are provided for the cooling power produced by
the non-Abelian anyon refrigerator, and its implementation in non-Abelian
fractional quantum Hall liquids is discussed
Damage growth in fibre bundle models with localized load sharing and environmentally-assisted ageing
Baryon electric dipole moments from strong CP violation
The electric dipole form factors and moments of the ground state baryons are
calculated in chiral perturbation theory at next-to-leading order. We show that
the baryon electric dipole form factors at this order depend only on two
combinations of low-energy constants. We also derive various relations that are
free of unknown low-energy constants. We use recent lattice QCD data to
calculate all baryon EDMs. In particular, we find d_n = -2.9\pm 0.9 and d_p =
1.1\pm 1.1 in units of 10^{-16} e \theta_0 cm. Finite volume corrections to the
moments are also worked out. We show that for a precision extraction from
lattice QCD data, the next-to-leading order terms have to be accounted for.Comment: 30 pages, 8 figures, to appear in JHE
Light quark mass dependence in heavy quarkonium physics
The issue of chiral extrapolations in heavy quarkonium systems is discussed.
We show that the light quark mass dependence of the properties of heavy
quarkonia is not always suppressed. For quarkonia close to an open flavor
threshold, even a nonanalytic chiral extrapolation is needed. Both these
nontrivial facts are demonstrated to appear in the decay widths of the hindered
M1 transitions between the first radially excited and ground state P-wave
charmonia. The results at a pion mass of about 500 MeV could deviate from the
value at the physical pion mass by a factor of two. Our findings show the
necessity of performing chiral extrapolations for lattice simulations of heavy
quarkonium systems.Comment: 5 pages, 5 figures. Version to appear in Phys. Rev. Let
Cumulants of the QCD topological charge distribution
The distribution of the QCD topological charge can be described by cumulants,
with the lowest one being the topological susceptibility. The vacuum energy
density in a theta-vacuum is the generating function for these cumulants. In
this paper, we derive the vacuum energy density in SU(2) chiral perturbation
theory up to next-to-leading order keeping different up and down quark masses,
which can be used to calculate any cumulant of the topological charge
distribution. We also give the expression for the case of SU(N) with degenerate
quark masses. In this case, all cumulants depend on the same linear combination
of low-energy constants and chiral logarithm, and thus there are sum rules
between the N-flavor quark condensate and the cumulants free of next-to-leading
order corrections.Comment: match the version published in PL
Knowledge Refinement via Rule Selection
In several different applications, including data transformation and entity
resolution, rules are used to capture aspects of knowledge about the
application at hand. Often, a large set of such rules is generated
automatically or semi-automatically, and the challenge is to refine the
encapsulated knowledge by selecting a subset of rules based on the expected
operational behavior of the rules on available data. In this paper, we carry
out a systematic complexity-theoretic investigation of the following rule
selection problem: given a set of rules specified by Horn formulas, and a pair
of an input database and an output database, find a subset of the rules that
minimizes the total error, that is, the number of false positive and false
negative errors arising from the selected rules. We first establish
computational hardness results for the decision problems underlying this
minimization problem, as well as upper and lower bounds for its
approximability. We then investigate a bi-objective optimization version of the
rule selection problem in which both the total error and the size of the
selected rules are taken into account. We show that testing for membership in
the Pareto front of this bi-objective optimization problem is DP-complete.
Finally, we show that a similar DP-completeness result holds for a bi-level
optimization version of the rule selection problem, where one minimizes first
the total error and then the size
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