22,625 research outputs found
On Linear Operator Channels over Finite Fields
Motivated by linear network coding, communication channels perform linear
operation over finite fields, namely linear operator channels (LOCs), are
studied in this paper. For such a channel, its output vector is a linear
transform of its input vector, and the transformation matrix is randomly and
independently generated. The transformation matrix is assumed to remain
constant for every T input vectors and to be unknown to both the transmitter
and the receiver. There are NO constraints on the distribution of the
transformation matrix and the field size.
Specifically, the optimality of subspace coding over LOCs is investigated. A
lower bound on the maximum achievable rate of subspace coding is obtained and
it is shown to be tight for some cases. The maximum achievable rate of
constant-dimensional subspace coding is characterized and the loss of rate
incurred by using constant-dimensional subspace coding is insignificant.
The maximum achievable rate of channel training is close to the lower bound
on the maximum achievable rate of subspace coding. Two coding approaches based
on channel training are proposed and their performances are evaluated. Our
first approach makes use of rank-metric codes and its optimality depends on the
existence of maximum rank distance codes. Our second approach applies linear
coding and it can achieve the maximum achievable rate of channel training. Our
code designs require only the knowledge of the expectation of the rank of the
transformation matrix. The second scheme can also be realized ratelessly
without a priori knowledge of the channel statistics.Comment: 53 pages, 3 figures, submitted to IEEE Transaction on Information
Theor
SUSY Dark Matter In Light Of CDMS/XENON Limits
In this talk we briefly review the current CDMS/XENON constraints on the
neutralino dark matter in three popular supersymmetric models: the minimal
(MSSM), the next-to-minimal (NMSSM) and the nearly minimal (nMSSM). The
constraints from the dark matter relic density and various collider experiments
are also taken into account. The conclusion is that for each model the current
CDMS/XENON limits can readily exclude a large part of the parameter space
allowed by other constraints and the future SuperCDMS or XENON100 can cover
most of the allowed parameter space. The implication for the Higgs search at
the LHC is also discussed. It is found that in the currently allowed parameter
space the MSSM charged Higgs boson is quite unlikely to be discovered at the
LHC while the neutral Higgs bosons and may be accessible at the LHC in
the parameter space with a large parameter.Comment: talk given at 2nd International Workshop on Dark Matter, Dark Energy
and Matter-Antimatter Asymmetry, Nov 5-6, 2010, Hsinchu, Taiwan (to appear in
Int. J. Mod. Phys. D
Estimating the central charge from the R\'enyi entanglement entropy
We calculate the von Neumann and R\'enyi bipartite entanglement entropy of
the model with a chemical potential on a 1+1 dimensional Euclidean
lattice with open and periodic boundary conditions. We show that the
Calabrese-Cardy conformal field theory predictions for the leading logarithmic
scaling with the spatial size of these entropies are consistent with a central
charge . This scaling survives the time continuum limit and truncations of
the microscopic degrees of freedom, modifications which allow us to connect the
Lagrangian formulation to quantum Hamiltonians. At half-filling, the forms of
the subleading corrections imposed by conformal field theory allow the
determination of the central charge with an accuracy better than two percent
for moderately sized lattices. We briefly discuss the possibility of estimating
the central charge using quantum simulators.Comment: 10 pages, 8 figures, 3 table
Top quark forward-backward asymmetry and charge asymmetry in left-right twin Higgs model
In order to explain the Tevatron anomaly of the top quark forward-backward
asymmetry in the left-right twin Higgs model, we choose to give up
the lightest neutral particle of field as a stable dark matter
candidate. Then a new Yukawa interaction for is allowed, which can be
free from the constraint of same-sign top pair production and contribute
sizably to . Considering the constraints from the production rates of
the top pair (), the top decay rates and invariant mass
distribution, we find that this model with such new Yukawa interaction can
explain measured at the Tevatron while satisfying the charge
asymmetry measured at the LHC.Moreover, this model predicts a
strongly correlation between at the LHC and at the
Tevatron, i.e., increases as increases.Comment: 17 pages, 9 figures; matches the published versio
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