1,927 research outputs found
Derivation of Matrix Product Ansatz for the Heisenberg Chain from Algebraic Bethe Ansatz
We derive a matrix product representation of the Bethe ansatz state for the
XXX and XXZ spin-1/2 Heisenberg chains using the algebraic Bethe ansatz. In
this representation, the components of the Bethe eigenstates are expressed as
traces of products of matrices which act on , the tensor
product of auxiliary spaces. By changing the basis in , we
derive explicit finite-dimensional representations for the matrices. These
matrices are the same as those appearing in the recently proposed matrix
product ansatz by Alcaraz and Lazo [Alcaraz F C and Lazo M J 2006 {\it J. Phys.
A: Math. Gen.} \textbf{39} 11335.] apart from normalization factors. We also
discuss the close relation between the matrix product representation of the
Bethe eigenstates and the six-vertex model with domain wall boundary conditions
[Korepin V E 1982 {\it Commun. Math. Phys.}, \textbf{86} 391.] and show that
the change of basis corresponds to a mapping from the six-vertex model to the
five-vertex model.Comment: 24 pages; minor typos are correcte
Entanglement entropy of two disjoint intervals in c=1 theories
We study the scaling of the Renyi entanglement entropy of two disjoint blocks
of critical lattice models described by conformal field theories with central
charge c=1. We provide the analytic conformal field theory result for the
second order Renyi entropy for a free boson compactified on an orbifold
describing the scaling limit of the Ashkin-Teller (AT) model on the self-dual
line. We have checked this prediction in cluster Monte Carlo simulations of the
classical two dimensional AT model. We have also performed extensive numerical
simulations of the anisotropic Heisenberg quantum spin-chain with tree-tensor
network techniques that allowed to obtain the reduced density matrices of
disjoint blocks of the spin-chain and to check the correctness of the
predictions for Renyi and entanglement entropies from conformal field theory.
In order to match these predictions, we have extrapolated the numerical results
by properly taking into account the corrections induced by the finite length of
the blocks to the leading scaling behavior.Comment: 37 pages, 23 figure
Paranasal sinuses opacification on magnetic resonance imaging in relation to brain health in sporadic small vessel disease â Systematic review and pilot analysis
Entanglement entropy of two disjoint blocks in XY chains
We study the Renyi entanglement entropies of two disjoint intervals in XY
chains. We exploit the exact solution of the model in terms of free Majorana
fermions and we show how to construct the reduced density matrix in the spin
variables by taking properly into account the Jordan-Wigner string between the
two blocks. From this we can evaluate any Renyi entropy of finite integer
order. We study in details critical XX and Ising chains and we show that the
asymptotic results for large blocks agree with recent conformal field theory
predictions if corrections to the scaling are included in the analysis
correctly. We also report results in the gapped phase and after a quantum
quench.Comment: 34 pages, 11 figure
Universal corrections to scaling for block entanglement in spin-1/2 XX chains
We consider the R\'enyi entropies in the one dimensional spin-1/2
Heisenberg XX chain in a magnetic field. The case n=1 corresponds to the von
Neumann ``entanglement'' entropy. Using a combination of methods based on the
generalized Fisher-Hartwig conjecture and a recurrence relation connected to
the Painlev\'e VI differential equation we obtain the asymptotic behaviour,
accurate to order , of the R\'enyi entropies
for large block lengths . For n=1,2,3,10 this constitutes the 3,6,10,48
leading terms respectively. The o(1) contributions are found to exhibit a rich
structure of oscillatory behaviour, which we analyze in some detail both for
finite and in the limit .Comment: 25 pages, 5 figure
Dietary Fibre in Pig's Diets: Effects on Greenhouse Gas Emissions from Slurry Storage to Field Application
Pigâs slurry is a key source of greenhouse gases (GHG). In Spain, GHG emissions (CH4+ N2O) from pig slurry (storage
and land application) accounted in 2011 for 18.4% of total GHG emissions (in CO2- equivalent) of the agriculture sector
according to the National Inventory Report (NIR). Slurry composition can be modified through diet manipulation.
The aim of this work was to evaluate the effect of different fibre types in fattening pigsâ diets on GHG emissions from
pig slurry storage and field application
A DNA barcode-assisted annotated checklist of the spider (Arachnida, Araneae) communities associated to white oak woodlands in Spanish National Parks
Background: A large scale semi-quantitative biodiversity assessment was conducted in white oak woodlands in areas included in the Spanish Network of National Parks, as part of a project aimed at revealing biogeographic patterns and identify biodiversity drivers. The semiquantitative COBRA sampling protocol was conducted in sixteen 1-ha plots across six national parks using a nested design. All adult specimens were identified to species level based on morphology. Uncertain delimitations and identifications due to either limited information of diagnostic characters or conflicting taxonomy were further investigated using DNA barcode information. New information: We identified 376 species belonging to 190 genera in 39 families, from the 8,521 adults found amongst the 20,539 collected specimens. Faunistic results include the discovery of 7 new species to the Iberian Peninsula, 3 new species to Spain and 11 putative new species to science. As largely expected by environmental features, the southern parks showed a higher proportion of Iberian and Mediterranean species than the northern parks, where the Palearctic elements were largely dominant. The analysis of approximately 3,200 DNA barcodes generated in the present study, corroborated and provided finer resolution to the morphologically based delimitation and identification of specimens in some taxonomically challenging families. Specifically, molecular data confirmed putative new species with diagnosable morphology, identified overlooked lineages that may constitute new species, confirmed assignment of specimens of unknown sexes to species and identified cases of misidentifications and phenotypic polymorphisms
Experimental realization of on-chip topological nanoelectromechanical metamaterials
Topological mechanical metamaterials translate condensed matter phenomena,
like non-reciprocity and robustness to defects, into classical platforms. At
small scales, topological nanoelectromechanical metamaterials (NEMM) can enable
the realization of on-chip acoustic components, like unidirectional waveguides
and compact delay-lines for mobile devices. Here, we report the experimental
realization of NEMM phononic topological insulators, consisting of
two-dimensional arrays of free-standing silicon nitride (SiN) nanomembranes
that operate at high frequencies (10-20 MHz). We experimentally demonstrate the
presence of edge states, by characterizing their localization and Dirac
cone-like frequency dispersion. Our topological waveguides also exhibit
robustness to waveguide distortions and pseudospin-dependent transport. The
suggested devices open wide opportunities to develop functional acoustic
systems for high-frequency signal processing applications
Preclinical activity of LBH589 alone or in combination with chemotherapy in a xenogeneic mouse model of human acute lymphoblastic leukemia.
Histone deacetylases (HDACs) have been identified as therapeutic targets due to their regulatory function in chromatin structure and organization. Here, we analyzed the therapeutic effect of LBH589, a class I-II HDAC inhibitor, in acute lymphoblastic leukemia (ALL). In vitro, LBH589 induced dose-dependent antiproliferative and apoptotic effects, which were associated with increased H3 and H4 histone acetylation. Intravenous administration of LBH589 in immunodeficient BALB/c-RAG2(-/-)Îłc(-/-) mice in which human-derived T and B-ALL cell lines were injected induced a significant reduction in tumor growth. Using primary ALL cells, a xenograft model of human leukemia in BALB/c-RAG2(-/-)Îłc(-/-) mice was established, allowing continuous passages of transplanted cells to several mouse generations. Treatment of mice engrafted with T or B-ALL cells with LBH589 induced an in vivo increase in the acetylation of H3 and H4, which was accompanied with prolonged survival of LBH589-treated mice in comparison with those receiving vincristine and dexamethasone. Notably, the therapeutic efficacy of LBH589 was significantly enhanced in combination with vincristine and dexamethasone. Our results show the therapeutic activity of LBH589 in combination with standard chemotherapy in pre-clinical models of ALL and suggest that this combination may be of clinical value in the treatment of patients with ALL
Propuesta de un nuevo modelo microquirĂșrgico para el estudio de la endometriosis inducida en rata Wistar. Resultados preliminares
The current knowledge status on the patogenesis of endometriosis as well as devastating consequences of disease evolution in women's reproductive health, have promoted researchers advances in a great manner during last years. The immunologic and neangiogenesis systems implication have opened new ways of knowledge over classic theories from the beginning of the xx century. The experimental resesearch, using animal induction models. Below we explain the first steps a new induction model ("PGR1-HotDog"), based on Wistar rats using a new disease autogeneration system, created for te study of the early stages of the endometriosis
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