2,888 research outputs found
Finite-size scaling exponents and entanglement in the two-level BCS model
We analyze the finite-size properties of the two-level BCS model. Using the
continuous unitary transformation technique, we show that nontrivial scaling
exponents arise at the quantum critical point for various observables such as
the magnetization or the spin-spin correlation functions. We also discuss the
entanglement properties of the ground state through the concurrence which
appears to be singular at the transition.Comment: 4 pages, 3 figures, published versio
Violation of area-law scaling for the entanglement entropy in spin 1/2 chains
Entanglement entropy obeys area law scaling for typical physical quantum
systems. This may naively be argued to follow from locality of interactions. We
show that this is not the case by constructing an explicit simple spin chain
Hamiltonian with nearest neighbor interactions that presents an entanglement
volume scaling law. This non-translational model is contrived to have couplings
that force the accumulation of singlet bonds across the half chain. Our result
is complementary to the known relation between non-translational invariant,
nearest neighbor interacting Hamiltonians and QMA complete problems.Comment: 9 pages, 4 figure
Renormalization group transformations on quantum states
We construct a general renormalization group transformation on quantum
states, independent of any Hamiltonian dynamics of the system. We illustrate
this procedure for translational invariant matrix product states in one
dimension and show that product, GHZ, W and domain wall states are special
cases of an emerging classification of the fixed points of this
coarse--graining transformation.Comment: 5 pages, 2 figur
Continuous unitary transformations and finite-size scaling exponents in the Lipkin-Meshkov-Glick model
We analyze the finite-size scaling exponents in the Lipkin-Meshkov-Glick
model by means of the Holstein-Primakoff representation of the spin operators
and the continuous unitary transformations method. This combination allows us
to compute analytically leading corrections to the ground state energy, the
gap, the magnetization, and the two-spin correlation functions. We also present
numerical calculations for large system size which confirm the validity of this
approach. Finally, we use these results to discuss the entanglement properties
of the ground state focusing on the (rescaled) concurrence that we compute in
the thermodynamical limit.Comment: 20 pages, 9 figures, published versio
Half the entanglement in critical systems is distillable from a single specimen
We establish that the leading critical scaling of the single-copy
entanglement is exactly one half of the entropy of entanglement of a block in
critical infinite spin chains in a general setting, using methods of conformal
field theory. Conformal symmetry imposes that the single-copy entanglement for
critical many-body systems scales as E_1(\rho_L)=(c/6) \log L- (c/6)
(\pi^2/\log L) + O(1/L), where L is the number of constituents in a block of an
infinite chain and c corresponds to the central charge. This proves that from a
single specimen of a critical chain, already half the entanglement can be
distilled compared to the rate that is asymptotically available. The result is
substantiated by a quantitative analysis for all translationally invariant
quantum spin chains corresponding to general isotropic quasi-free fermionic
models. An analytic example of the XY model shows that away from criticality
the above simple relation is only maintained near the quantum phase transition
point.Comment: 4 pages RevTeX, 1 figure, final versio
¿Existe alguna relación entre la capacidad de movimiento funcional y el estado ponderal? Un estudio en escolares españoles
Indexación: Scopus.Background: to examine relations between functional movement patterns and weight status in Spanish primary school children and to determine the differences between sexes. Methods: three hundred and thirty-three, 6-13 years old children (164 boys and 169 girls), participated in this study. The main outcome measures were the body mass index (BMI) and the Functional Movement Screen™ (FMS). Children were classified as normal weight (NW), overweight (OV) or obese (OB) according to international cut-offs. Results: total FMS score was negatively correlated with BMI (p < 0.001). FMS score was different between children from NW, OV and OB groups (p = 0.001), lower with the increased BMI (p < 0.001 between all groups). Significant differences (p < 0.05) between NW, OV and OB were found in deep squat, hurdle step, in-line lunge, shoulder mobility, straight leg-raise and push-up tests. As for the sex differences, girls obtained higher scores (p < 0.05) in in-line lunge, shoulder mobility and straight leg-raise, whereas boys did it in push-up (p = 0.044) test. Conclusions: these results confirm that total FMS score significantly and inversely correlates with BMI in a group of 333 school-age children. As for the sex differences, girls outperform boys in movements requiring flexibility and balance, whilst boys outperform girls in tests where muscular strength is required. © 2018 SENPE and Arán Ediciones S.L.Introducción: examinar la relación entre los patrones de movimiento funcional y el estado ponderal en escolares españoles, determinando
también la infl uencia de la variable sexo.
Métodos: trescientos treinta y tres niños de 6-13 años de edad (164 niños y 169 niñas), participaron voluntariamente en este estudio. Las
variables objeto de estudio fueron el índice de masa corporal (IMC) y la batería de test Functional Movement ScreenTM (FMS). Los niños fueron
clasifi cados como normopeso (NW), sobrepeso (OV) y obesos (OB) de acuerdo con los puntos de corte internacionales.
Resultados: la puntuación total en el FMS correlacionó de forma negativa y signifi cativa con el IMC (p < 0,001). La puntuación en FMS fue
diferente entre las categorías de peso (p = 0,001), hallando un peor rendimiento en FMS conforme aumenta el IMC (p < 0,001 entre todos los
grupos). Se hallaron diferencias signifi cativas (p < 0,05) entre NW, OV y OB en los test de deep squat, hurdle step, in-line lunge, shoulder mobility,
straight leg-raise and push-up. En cuanto a las diferencias por sexo, las chicas obtuvieron puntuaciones más altas en FMS (p < 0,05) en los test
in-line lunge, shoulder mobility and straight leg-raise; mientras los chicos obtuvieron puntuaciones superiores en el test de push-up (p = 0,044).
Conclusiones: los resultados confi rman que la puntuación total en el FMS correlaciona signifi cativa y negativamente con el IMC en este grupo
de 333 escolares. En cuanto a la infl uencia del sexo, las chicas obtuvieron mayor puntuación que los chicos en los test que requerían fl exibilidad
y equilibrio, mientras los chicos fueron superiores en los test en los que predominaba la fuerza muscular.https://www.nutricionhospitalaria.org/index.php/articles/01670/show#
Valence Bond Entanglement Entropy
We introduce for SU(2) quantum spin systems the Valence Bond Entanglement
Entropy as a counting of valence bond spin singlets shared by two subsystems.
For a large class of antiferromagnetic systems, it can be calculated in all
dimensions with Quantum Monte Carlo simulations in the valence bond basis. We
show numerically that this quantity displays all features of the von Neumann
entanglement entropy for several one-dimensional systems. For two-dimensional
Heisenberg models, we find a strict area law for a Valence Bond Solid state and
multiplicative logarithmic corrections for the Neel phase.Comment: 4 pages, 3 figures, v2: small corrections, published versio
GHZ extraction yield for multipartite stabilizer states
Let be an arbitrary stabilizer state distributed between three
remote parties, such that each party holds several qubits. Let be a
stabilizer group of . We show that can be converted by local
unitaries into a collection of singlets, GHZ states, and local one-qubit
states. The numbers of singlets and GHZs are determined by dimensions of
certain subgroups of . For an arbitrary number of parties we find a
formula for the maximal number of -partite GHZ states that can be extracted
from by local unitaries. A connection with earlier introduced measures
of multipartite correlations is made. An example of an undecomposable
four-party stabilizer state with more than one qubit per party is given. These
results are derived from a general theoretical framework that allows one to
study interconversion of multipartite stabilizer states by local Clifford group
operators. As a simple application, we study three-party entanglement in
two-dimensional lattice models that can be exactly solved by the stabilizer
formalism.Comment: 12 pages, 1 figur
Radiation and magnetic field effects on new semiconductor power devices for HL-LHC experiments
The radiation hardness of commercial Silicon Carbide and Gallium Nitride
power MOSFETs is presented in this paper, for Total Ionizing Dose effects and
Single Event Effects, under gamma, neutrons, protons and heavy ions. Similar
tests are discussed for commercial DC-DC converters, also tested in operation
under magnetic field
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