10,065 research outputs found
Exact valence bond entanglement entropy and probability distribution in the XXX spin chain and the Potts model
By relating the ground state of Temperley-Lieb hamiltonians to partition
functions of 2D statistical mechanics systems on a half plane, and using a
boundary Coulomb gas formalism, we obtain in closed form the valence bond
entanglement entropy as well as the valence bond probability distribution in
these ground states. We find in particular that for the XXX spin chain, the
number N_c of valence bonds connecting a subsystem of size L to the outside
goes, in the thermodynamic limit, as = (4/pi^2) ln L, disproving a recent
conjecture that this should be related with the von Neumann entropy, and thus
equal to 1/(3 ln 2) ln L. Our results generalize to the Q-state Potts model.Comment: 4 pages, 2 figure
High-energy neutrino fluxes from AGN populations inferred from X-ray surveys
High-energy neutrinos and photons are complementary messengers, probing
violent astrophysical processes and structural evolution of the Universe. X-ray
and neutrino observations jointly constrain conditions in active galactic
nuclei (AGN) jets: their baryonic and leptonic contents, and particle
production efficiency. Testing two standard neutrino production models for
local source Cen A \citep{KT2008,BB2009}, we calculate the high-energy neutrino
spectra of single AGN sources and derive the flux of high-energy neutrinos
expected for the current epoch. Assuming that accretion determines both X-rays
and particle creation, our parametric scaling relations predict neutrino yield
in various AGN classes. We derive redshift-dependent number densities of each
class, from {\it Chandra} and {\it Swift}/BAT X-ray luminosity functions
\citep{SGB2008,ACS2009}. We integrate the neutrino spectrum expected from the
cumulative history of AGN (correcting for cosmological and source effects, e.g.
jet orientation and beaming). Both emission scenarios yield neutrino fluxes
well above limits set by {\it IceCube} (by -- at 1 PeV,
depending on the assumed jet models for neutrino production). This implies
that: (i) Cen A might not be a typical neutrino source as commonly assumed;
(ii) both neutrino production models overestimate the efficiency; (iii)
neutrino luminosity scales with accretion power differently among AGN classes
and hence does not follow X-ray luminosity universally; (iv) some AGN are
neutrino-quiet (e.g. below a power threshold for neutrino production); (v)
neutrino and X-ray emission have different duty cycles (e.g. jets alternate
between baryonic and leptonic flows); or (vi) some combination of the above.Comment: 16 pages, 6 figures, 3 tables, accepted for publication in MNRA
Hard hexagon partition function for complex fugacity
We study the analyticity of the partition function of the hard hexagon model
in the complex fugacity plane by computing zeros and transfer matrix
eigenvalues for large finite size systems. We find that the partition function
per site computed by Baxter in the thermodynamic limit for positive real values
of the fugacity is not sufficient to describe the analyticity in the full
complex fugacity plane. We also obtain a new algebraic equation for the low
density partition function per site.Comment: 49 pages, IoP styles files, lots of figures (png mostly) so using
PDFLaTeX. Some minor changes added to version 2 in response to referee
report
Integrability vs non-integrability: Hard hexagons and hard squares compared
In this paper we compare the integrable hard hexagon model with the
non-integrable hard squares model by means of partition function roots and
transfer matrix eigenvalues. We consider partition functions for toroidal,
cylindrical, and free-free boundary conditions up to sizes and
transfer matrices up to 30 sites. For all boundary conditions the hard squares
roots are seen to lie in a bounded area of the complex fugacity plane along
with the universal hard core line segment on the negative real fugacity axis.
The density of roots on this line segment matches the derivative of the phase
difference between the eigenvalues of largest (and equal) moduli and exhibits
much greater structure than the corresponding density of hard hexagons. We also
study the special point of hard squares where all eigenvalues have unit
modulus, and we give several conjectures for the value at of the
partition functions.Comment: 46 page
On the universality of compact polymers
Fully packed loop models on the square and the honeycomb lattice constitute
new classes of critical behaviour, distinct from those of the low-temperature
O(n) model. A simple symmetry argument suggests that such compact phases are
only possible when the underlying lattice is bipartite. Motivated by the hope
of identifying further compact universality classes we therefore study the
fully packed loop model on the square-octagon lattice. Surprisingly, this model
is only critical for loop weights n < 1.88, and its scaling limit coincides
with the dense phase of the O(n) model. For n=2 it is exactly equivalent to the
selfdual 9-state Potts model. These analytical predictions are confirmed by
numerical transfer matrix results. Our conclusions extend to a large class of
bipartite decorated lattices.Comment: 13 pages including 4 figure
Lack of detectable DNA uptake by transmission of selected recipients in mono-associated rats
An important concern revealed in the public discussion of the use of genetically modified (GM) plants for human consumption, is the potential transfer of DNA from these plants to bacteria present in the gastrointestinal tract. Especially, there is a concern that antibiotic resistance genes used for the construction of GM plants end up in pathogenic bacteria, eventually leading to untreatable disease. Three different bacterial species (Escherichia coli, Bacillus subtilis, Streptococcus gordonii), all natural inhabitants of the food and intestinal tract environment were used as recipients for uptake of DNA. As source of DNA both plasmid and genomic DNA from GM plants were used in in vitro and in vivo transformation studies. Mono-associated rats, creating a worst-case scenario, did not give rise to any detectable transfer of DNA. Although we were unable to detect any transformation events in our experiment, it cannot be ruled out that this could happen in the GI tract. However, since several steps are required before expression of plant-derived DNA in intestinal bacteria, we believe this is unlikely, and antibiotic resistance development in this environment is more in danger by the massive use of antibiotics than the consumption of GM food harbouring antibiotic resistance genes
Performance evaluation of an emergency call center: tropical polynomial systems applied to timed Petri nets
We analyze a timed Petri net model of an emergency call center which
processes calls with different levels of priority. The counter variables of the
Petri net represent the cumulated number of events as a function of time. We
show that these variables are determined by a piecewise linear dynamical
system. We also prove that computing the stationary regimes of the associated
fluid dynamics reduces to solving a polynomial system over a tropical
(min-plus) semifield of germs. This leads to explicit formul{\ae} expressing
the throughput of the fluid system as a piecewise linear function of the
resources, revealing the existence of different congestion phases. Numerical
experiments show that the analysis of the fluid dynamics yields a good
approximation of the real throughput.Comment: 21 pages, 4 figures. A shorter version can be found in the
proceedings of the conference FORMATS 201
Sound velocity and absorption measurements under high pressure using picosecond ultrasonics in diamond anvil cell. Application to the stability study of AlPdMn
We report an innovative high pressure method combining the diamond anvil cell
device with the technique of picosecond ultrasonics. Such an approach allows to
accurately measure sound velocity and attenuation of solids and liquids under
pressure of tens of GPa, overcoming all the drawbacks of traditional
techniques. The power of this new experimental technique is demonstrated in
studies of lattice dynamics, stability domain and relaxation process in a
metallic sample, a perfect single-grain AlPdMn quasicrystal, and rare gas, neon
and argon. Application to the study of defect-induced lattice stability in
AlPdMn up to 30 GPa is proposed. The present work has potential for application
in areas ranging from fundamental problems in physics of solid and liquid
state, which in turn could be beneficial for various other scientific fields as
Earth and planetary science or material research
River and Inshore Beam Trawl Fishery Scoping Study
The Queensland Ecological Risk Assessment Guideline (the Guideline) was released in March 2018 as part of the Queensland Sustainable Fisheries Strategy 2017–2027. This Guideline provides an overview of strategy being employed to develop Ecological Risk Assessments (ERAs) for Queensland’s fisheries. The Guideline describes a four-stage framework consisting of a Scoping Study; a Level 1, whole of fishery qualitative assessment; a Level 2, species-specific semi-quantitative or low-data quantitative assessment and; a Level 3 quantitative assessment (if applicable).
The Scoping Study establishes a baseline of information on the key characteristics of the River and Inshore Beam Trawl Fishery (RIBTF). It includes information on the broader management regime, key species, gear configurations and catch and effort trends. Information contained in the scoping study for the RIBTF will be used to inform subsequent assessments including the whole of fishery (Level 1) and species-specific (Level 2)
Gulf of Carpentaria Inshore Fin Fish Fishery Scoping Study
The Queensland Ecological Risk Assessment Guideline (the Guideline) was released in March 2018 as part of the Queensland Sustainable Fisheries Strategy 2017–2027. This Guideline provides an overview of strategy being employed to develop Ecological Risk Assessments (ERAs) for Queensland’s fisheries. The Guideline describes a four-stage framework consisting of a Scoping Study; a Level 1, whole of fishery qualitative assessment; a Level 2, species-specific semi-quantitative or low-data quantitative assessment and; a Level 3 quantitative assessment (if applicable).
The Scoping Study establishes a baseline of information on the key characteristics of the Gulf of Carpentaria Inshore Fin Fish Fishery (GOCIFFF). It includes information on the broader management regime, key species, gear configurations and catch and effort trends. Information contained in the scoping study for the GOCIFFF will be used to inform subsequent assessments including the whole of fishery (Level 1) and species-specific (Level 2)
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