562 research outputs found
Entanglement Structure of Deconfined Quantum Critical Points
We study the entanglement properties of deconfined quantum critical points.
We show not only that these critical points may be distinguished by their
entanglement structure but also that they are in general more highly entangled
that conventional critical points. We primarily focus on computations of the
entanglement entropy of deconfined critical points in 2+1 dimensions, drawing
connections to topological entanglement entropy and a recent conjecture on the
monotonicity under RG flow of universal terms in the entanglement entropy. We
also consider in some detail a variety of issues surrounding the extraction of
universal terms in the entanglement entropy. Finally, we compare some of our
results to recent numerical simulations.Comment: 12 pages, 4 figure
Quenched vs Annealed: Glassiness from SK to SYK
We show that any SYK-like model with finite-body interactions among
\textit{local} degrees of freedom, e.g., bosons or spins, has a fundamental
difference from the standard fermionic model: the former fails to be described
by an annealed free energy at low temperature. In this respect, such models
more closely resemble spin glasses. We demonstrate this by two means: first, a
general theorem proving that the annealed free energy is divergent at low
temperature in any model with a tensor product Hilbert space; and second, a
replica treatment of two prominent examples which exhibit phase transitions
from an "annealed" phase to a "non-annealed" phase as a function of
temperature. We further show that this effect appears only at 'th order
in a expansion, even though lower-order terms misleadingly seem to
converge. Our results prove that the non-bosonic nature of the particles in SYK
is an essential ingredient for its physics, highlight connections between local
models and spin glasses, and raise important questions as to the role of
fermions and/or glassiness in holography.Comment: 13 pages of main text, 4 pages of appendix, 4 figure
Correlated Topological Insulators and the Fractional Magnetoelectric Effect
Topological insulators are characterized by the presence of gapless surface
modes protected by time-reversal symmetry. In three space dimensions the
magnetoelectric response is described in terms of a bulk theta term for the
electromagnetic field. Here we construct theoretical examples of such phases
that cannot be smoothly connected to any band insulator. Such correlated
topological insulators admit the possibility of fractional magnetoelectric
response described by fractional theta/pi. We show that fractional theta/pi is
only possible in a gapped time reversal invariant system of bosons or fermions
if the system also has deconfined fractional excitations and associated
degenerate ground states on topologically non-trivial spaces. We illustrate
this result with a concrete example of a time reversal symmetric topological
insulator of correlated bosons with theta = pi/4. Extensions to electronic
fractional topological insulators are briefly described.Comment: 4 pages + ref
Rigorous free fermion entanglement renormalization from wavelet theory
We construct entanglement renormalization schemes which provably approximate
the ground states of non-interacting fermion nearest-neighbor hopping
Hamiltonians on the one-dimensional discrete line and the two-dimensional
square lattice. These schemes give hierarchical quantum circuits which build up
the states from unentangled degrees of freedom. The circuits are based on pairs
of discrete wavelet transforms which are approximately related by a
"half-shift": translation by half a unit cell. The presence of the Fermi
surface in the two-dimensional model requires a special kind of circuit
architecture to properly capture the entanglement in the ground state. We show
how the error in the approximation can be controlled without ever performing a
variational optimization.Comment: 15 pages, 10 figures, one theore
Entangled Dilaton Dyons
Einstein-Maxwell theory coupled to a dilaton is known to give rise to
extremal solutions with hyperscaling violation. We study the behaviour of these
solutions in the presence of a small magnetic field. We find that in a region
of parameter space the magnetic field is relevant in the infra-red and
completely changes the behaviour of the solution which now flows to an
attractor. As a result there is an extensive ground state
entropy and the entanglement entropy of a sufficiently big region on the
boundary grows like the volume. In particular, this happens for values of
parameters at which the purely electric theory has an entanglement entropy
growing with the area, , like which is believed to be a
characteristic feature of a Fermi surface. Some other thermodynamic properties
are also analysed and a more detailed characterisation of the entanglement
entropy is also carried out in the presence of a magnetic field. Other regions
of parameter space not described by the end point are also
discussed.Comment: Some comments regarding comparison with weakly coupled Fermi liquid
changed, typos corrected and caption of a figure modifie
Population-genomic insights into emergence, crop-adaptation, and dissemination of Pseudomonas syringae pathogens
This is the author accepted manuscript. The final version is available from the publisher via the DOI in this record.Many bacterial pathogens are well characterized but, in some cases, relatively little is
known about the populations from which they emerged. This limits understanding of
the molecular mechanisms underlying disease. The crop pathogen Pseudomonas
syringae sensu lato has been widely isolated from the environment, including wild
plants and components of the water cycle, and causes disease in several economically
important crops. Here, we compared genome sequences of 45 P. syringae crop
pathogen outbreak strains with 69 closely related environmental isolates. Phylogenetic
reconstruction revealed that crop pathogens emerged many times independently from
environmental populations. Unexpectedly, differences in gene content between
environmental populations and outbreak strains were minimal with most virulence
genes present in both. However, a genome-wide association study identified a small
number of genes, including the type III effector genes hopQ1 and hopD1, to be
associated with crop pathogens, but not with environmental populations, suggesting
that this small group of genes may play an important role in crop disease emergence.
Intriguingly, genome-wide analysis of homologous recombination revealed that the
locus Psyr 0346, predicted to encode a protein that confers antibiotic resistance, has
been frequently exchanged among lineages and thus may contribute to pathogen
fitness. Finally, we found that isolates from diseased crops and from components of the
water cycle, collected during the same crop disease epidemic, form a single
population. This provides the strongest evidence yet that precipitation and irrigation
water are an overlooked inoculum source for disease epidemics caused by P.
syringae.Caroline L. Monteil
received support from INRA and the European Union, in the framework of the Marie-Curie FP7
COFUND People Programme, through the award of an AgreenSkills’ fellowship (under grant
agreement n° 267196). Research in Boris A. Vinatzer’s laboratory and genome sequencing was
funded by the National Science Foundation of the USA (grants IOS-1354215 and DEB-1241068).
Funding for work in the Vinatzer laboratory was also provided in part by the Virginia Agricultural
Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S.
Department of Agriculture. Work carried out in the Sheppard laboratory was supported by the
Medical Research Council (MRC) grant MR/L015080/1, and the Wellcome Trust grant
088786/C/09/Z. GM was supported by a NISCHR Health Research Fellowship (HF-14-13)
The Gravity Dual of a Density Matrix
For a state in a quantum field theory on some spacetime, we can associate a
density matrix to any subset of a given spacelike slice by tracing out the
remaining degrees of freedom. In the context of the AdS/CFT correspondence, if
the original state has a dual bulk spacetime with a good classical description,
it is natural to ask how much information about the bulk spacetime is carried
by the density matrix for such a subset of field theory degrees of freedom. In
this note, we provide several constraints on the largest region that can be
fully reconstructed, and discuss specific proposals for the geometric
construction of this dual region.Comment: 19 pages, LaTeX, 8 figures, v2: footnote and reference adde
Quantum circuit approximations and entanglement renormalization for the Dirac field in 1+1 dimensions
The multiscale entanglement renormalization ansatz describes quantum many-body states
by a hierarchical entanglement structure organized by length scale. Numerically, it has been
demonstrated to capture critical lattice models and the data of the corresponding conformal
field theories with high accuracy. However, a rigorous understanding of its success and precise
relation to the continuum is still lacking. To address this challenge, we provide an explicit
construction of entanglement-renormalization quantum circuits that rigorously approximate
correlation functions of the massless Dirac conformal field theory. We directly target the
continuum theory: discreteness is introduced by our choice of how to probe the system, not
by any underlying short-distance lattice regulator. To achieve this, we use multiresolution
analysis from wavelet theory to obtain an approximation scheme and to implement entanglement
renormalization in a natural way. This could be a starting point for constructing quantum circuit
approximations for more general conformal field theories
Cube law, condition factor and weight-length relationships: history, meta-analysis and recommendations
This study presents a historical review, a meta-analysis, and recommendations for users about weight–length relationships, condition factors and relative weight equations. The historical review traces the developments of the respective concepts. The meta-analysis explores 3929 weight–length relationships of the type W = aLb for 1773 species of fishes. It shows that 82% of the variance in a plot of log a over b can be explained by allometric versus isometric growth patterns and by different body shapes of the respective species. Across species median b = 3.03 is significantly larger than 3.0, thus indicating a tendency towards slightly positive-allometric growth (increase in relative body thickness or plumpness) in most fishes. The expected range of 2.5 < b < 3.5 is confirmed. Mean estimates of b outside this range are often based on only one or two weight–length relationships per species. However, true cases of strong allometric growth do exist and three examples are given. Within species, a plot of log a vs b can be used to detect outliers in weight–length relationships. An equation to calculate mean condition factors from weight–length relationships is given as Kmean = 100aLb−3. Relative weight Wrm = 100W/(amLbm) can be used for comparing the condition of individuals across populations, where am is the geometric mean of a and bm is the mean of b across all available weight–length relationships for a given species. Twelve recommendations for proper use and presentation of weight–length relationships, condition factors and relative weight are given
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