19,376 research outputs found
The Unhiggs
We examine a scenario where the Higgs is part of an approximate conformal
field theory, and has a scaling dimension greater than one. Such an unparticle
Higgs (or Unhiggs) can still break electroweak symmetry and unitarize WW
scattering, but its gauge couplings are suppressed. An Unhiggs model has a
reduced sensitivity of the weak scale to the cutoff, and can thus provide a
solution to the little hierarchy problem.Comment: 21 pages, 9 figures; v2: further discussion, references added,
version published in JHE
Raman-scattering study of the phonon dispersion in twisted bi-layer graphene
Bi-layer graphene with a twist angle \theta\ between the layers generates a
superlattice structure known as Moir\'{e} pattern. This superlattice provides a
\theta-dependent q wavevector that activates phonons in the interior of the
Brillouin zone. Here we show that this superlattice-induced Raman scattering
can be used to probe the phonon dispersion in twisted bi-layer graphene (tBLG).
The effect reported here is different from the broadly studied double-resonance
in graphene-related materials in many aspects, and despite the absence of
stacking order in tBLG, layer breathing vibrations (namely ZO' phonons) are
observed.Comment: 18 pages, 4 figures, research articl
On the generalized Feng-Rao numbers of numerical semigroups generated by intervals
We give some general results concerning the computation of the generalized
Feng-Rao numbers of numerical semigroups. In the case of a numerical semigroup
generated by an interval, a formula for the Feng-Rao number is
obtained.Comment: 23 pages, 6 figure
Topological Quantum Error Correction with Optimal Encoding Rate
We prove the existence of topological quantum error correcting codes with
encoding rates asymptotically approaching the maximum possible value.
Explicit constructions of these topological codes are presented using surfaces
of arbitrary genus. We find a class of regular toric codes that are optimal.
For physical implementations, we present planar topological codes.Comment: REVTEX4 file, 5 figure
Numerical semigroups problem list
We propose a list of open problems in numerical semigroups.Comment: To appear in the CIM Bulletin, number 33. (http://www.cim.pt/) 13
page
Quantum control on entangled bipartite qubits
Ising interaction between qubits could produce distortion in entangled pairs
generated for engineering purposes (as in quantum computation) in presence of
parasite magnetic fields, destroying or altering the expected behavior of
process in which is projected to be used. Quantum control could be used to
correct that situation in several ways. Sometimes the user should be make some
measurement upon the system to decide which is the best control scheme; other
posibility is try to reconstruct the system using similar procedures without
perturbate it. In the complete pictures both schemes are present. We will work
first with pure systems studying advantages of different procedures. After, we
will extend these operations when time of distortion is uncertain, generating a
mixed state, which needs to be corrected by suposing the most probably time of
distortion.Comment: 10 pages, 5 figure
Homological Error Correction: Classical and Quantum Codes
We prove several theorems characterizing the existence of homological error
correction codes both classically and quantumly. Not every classical code is
homological, but we find a family of classical homological codes saturating the
Hamming bound. In the quantum case, we show that for non-orientable surfaces it
is impossible to construct homological codes based on qudits of dimension
, while for orientable surfaces with boundaries it is possible to
construct them for arbitrary dimension . We give a method to obtain planar
homological codes based on the construction of quantum codes on compact
surfaces without boundaries. We show how the original Shor's 9-qubit code can
be visualized as a homological quantum code. We study the problem of
constructing quantum codes with optimal encoding rate. In the particular case
of toric codes we construct an optimal family and give an explicit proof of its
optimality. For homological quantum codes on surfaces of arbitrary genus we
also construct a family of codes asymptotically attaining the maximum possible
encoding rate. We provide the tools of homology group theory for graphs
embedded on surfaces in a self-contained manner.Comment: Revtex4 fil
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