1,455 research outputs found
Topological Entanglement Entropy of a Bose-Hubbard Spin Liquid
The Landau paradigm of classifying phases by broken symmetries was
demonstrated to be incomplete when it was realized that different quantum Hall
states could only be distinguished by more subtle, topological properties.
Today, the role of topology as an underlying description of order has branched
out to include topological band insulators, and certain featureless gapped Mott
insulators with a topological degeneracy in the groundstate wavefunction.
Despite intense focus, very few candidates for these topologically ordered
"spin liquids" exist. The main difficulty in finding systems that harbour spin
liquid states is the very fact that they violate the Landau paradigm, making
conventional order parameters non-existent. Here, we uncover a spin liquid
phase in a Bose-Hubbard model on the kagome lattice, and measure its
topological order directly via the topological entanglement entropy. This is
the first smoking-gun demonstration of a non-trivial spin liquid, identified
through its entanglement entropy as a gapped groundstate with emergent Z2 gauge
symmetry.Comment: 4+ pages, 3 figure
Operator entanglement of two-qubit joint unitary operations revisited: Schmidt number approach
Operator entanglement of two-qubit joint unitary operations is revisited.
Schmidt number is an important attribute of a two-qubit unitary operation, and
may have connection with the entanglement measure of the unitary operator. We
found the entanglement measure of two-qubit unitary operators is classified by
the Schmidt number of the unitary operators. The exact relation between the
operator entanglement and the parameters of the unitary operator is clarified
too.Comment: To appear in the Brazilian Journal of Physic
CNV analysis in Chinese children of mental retardation highlights a sex differentiation in parental contribution to de novo and inherited mutational burdens
Rare copy number variations (CNVs) are a known genetic etiology in neurodevelopmental disorders (NDD). Comprehensive CNV analysis was performed in 287 Chinese children with mental retardation and/or development delay (MR/DD) and their unaffected parents. When compared with 5,866 ancestry-matched controls, 11~12% more MR/DD children carried rare and large CNVs. The increased CNV burden in MR/DD was predominantly due to de novo CNVs, the majority of which (62%) arose in the paternal germline. We observed a 2~3 fold increase of large CNV burden in the mothers of affected children. By implementing an evidence-based review approach, pathogenic structural variants were identified in 14.3% patients and 2.4% parents, respectively. Pathogenic CNVs in parents were all carried by mothers. The maternal transmission bias of deleterious CNVs was further replicated in a published dataset. Our study confirms the pathogenic role of rare CNVs in MR/DD, and provides additional evidence to evaluate the dosage sensitivity of some candidate genes. It also supports a population model of MR/DD that spontaneous mutations in males’ germline are major contributor to the de novo mutational burden in offspring, with higher penetrance in male than female; unaffected carriers of causative mutations, mostly females, then contribute to the inherited mutational burden.published_or_final_versio
Vacuum Alignment in SUSY A4 Models
In this note we discuss the vacuum alignment in supersymmetric models with
spontaneously broken flavour symmetries in the presence of soft supersymmetry
(SUSY) breaking terms. We show that the inclusion of soft SUSY breaking terms
can give rise to non-vanishing vacuum expectation values (VEVs) for the
auxiliary components of the flavon fields. These non-zero VEVs can have an
important impact on the phenomenology of this class of models, since they can
induce an additional flavour violating contribution to the sfermion soft mass
matrix of right-left (RL) type. We carry out an explicit computation in a class
of SUSY A4 models predicting tri-bimaximal mixing in the lepton sector. The
flavour symmetry breaking sector is described in terms of flavon and driving
supermultiplets. We find non-vanishing VEVs for the auxiliary components of the
flavon fields and for the scalar components of the driving fields which are of
order m_{SUSY} x and m_{SUSY}, respectively. Thereby, m_{SUSY} is the
generic soft SUSY breaking scale which is expected to be around 1 TeV and
is the VEV of scalar components of the flavon fields. Another effect of these
VEVs can be the generation of a mu term.Comment: 23 pages; added a new section on the relation to Supergravity;
version accepted for publication in JHE
In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth's magnetotail
Magnetic reconnection is one of the most important processes in
astrophysical, space and laboratory plasmas. Identifying the structure around
the point at which the magnetic field lines break and subsequently reform,
known as the magnetic null point, is crucial to improving our understanding
reconnection. But owing to the inherently three-dimensional nature of this
process, magnetic nulls are only detectable through measurements obtained
simultaneously from at least four points in space. Using data collected by the
four spacecraft of the Cluster constellation as they traversed a diffusion
region in the Earth's magnetotail on 15 September, 2001, we report here the
first in situ evidence for the structure of an isolated magnetic null. The
results indicate that it has a positive-spiral structure whose spatial extent
is of the same order as the local ion inertial length scale, suggesting that
the Hall effect could play an important role in 3D reconnection dynamics.Comment: 14 pages, 4 figure
Lineage Divergence and Historical Gene Flow in the Chinese Horseshoe Bat (Rhinolophus sinicus)
PMCID: PMC3581519This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Non-universal minimal Z' models: present bounds and early LHC reach
We consider non-universal 'minimal' Z' models, whose additional U(1) charge
is a non-anomalous linear combination of the weak hypercharge Y, the baryon
number B and the partial lepton numbers (L_e, L_mu, L_tau), with no exotic
fermions beyond three standard families with right-handed neutrinos. We show
that the observed pattern of neutrino masses and mixing can be fully reproduced
by a gauge-invariant renormalizable Lagrangian, and flavor-changing neutral
currents in the charged lepton sector are suppressed by a GIM mechanism. We
then discuss the phenomenology of some benchmark models. The electrophilic
B-3L_e model is significantly constrained by electroweak precision tests, but
still allows to fit the hint of an excess observed by CDF in dielectrons but
not in dimuons. The muonphilic B-3L_mu model is very mildly constrained by
electroweak precision tests, so that even the very early phase of the LHC can
explore significant areas of parameter space. We also discuss the hadrophobic
L_mu-L_tau model, which has recently attracted interest in connection with some
puzzling features of cosmic ray spectra.Comment: 29 pages, 13 figure
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