1,994 research outputs found
Quantum Phase Transitions detected by a local probe using Time Correlations and Violations of Leggett-Garg Inequalities
In the present paper we introduce a way of identifying quantum phase
transitions of many-body systems by means of local time correlations and
Leggett-Garg inequalities. This procedure allows to experimentally determine
the quantum critical points not only of finite-order transitions but also those
of infinite order, as the Kosterlitz-Thouless transition that is not always
easy to detect with current methods. By means of simple analytical arguments
for a general spin- Hamiltonian, and matrix product simulations of
one-dimensional and anisotropic models, we argue that
finite-order quantum phase transitions can be determined by singularities of
the time correlations or their derivatives at criticality. The same features
are exhibited by corresponding Leggett-Garg functions, which noticeably
indicate violation of the Leggett-Garg inequalities for early times and all the
Hamiltonian parameters considered. In addition, we find that the infinite-order
transition of the model at the isotropic point can be revealed by the
maximal violation of the Leggett-Garg inequalities. We thus show that quantum
phase transitions can be identified by purely local measurements, and that
many-body systems constitute important candidates to observe experimentally the
violation of Leggett-Garg inequalities.Comment: Minor changes, 11 pages, 11 figures. Final version published in Phys.
Rev.
Thermodynamics of noncommutative quantum Kerr black holes
Thermodynamic formalism for rotating black holes, characterized by
noncommutative and quantum corrections, is constructed. From a fundamental
thermodynamic relation, equations of state and thermodynamic response functions
are explicitly given and the effect of noncommutativity and quantum correction
is discussed. It is shown that the well known divergence exhibited in specific
heat is not removed by any of these corrections. However, regions of
thermodynamic stability are affected by noncommutativity, increasing the
available states for which some thermodynamic stability conditions are
satisfied.Comment: 16 pages, 9 figure
Dynamics of Entanglement and the Schmidt Gap in a Driven Light-Matter System
The ability to modify light-matter coupling in time (e.g. using external
pulses) opens up the exciting possibility of generating and probing new aspects
of quantum correlations in many-body light-matter systems. Here we study the
impact of such a pulsed coupling on the light-matter entanglement in the Dicke
model as well as the respective subsystem quantum dynamics. Our dynamical
many-body analysis exploits the natural partition between the radiation and
matter degrees of freedom, allowing us to explore time-dependent
intra-subsystem quantum correlations by means of squeezing parameters, and the
inter-subsystem Schmidt gap for different pulse duration (i.e. ramping
velocity) regimes -- from the near adiabatic to the sudden quench limits. Our
results reveal that both types of quantities indicate the emergence of the
superradiant phase when crossing the quantum critical point. In addition, at
the end of the pulse light and matter remain entangled even though they become
uncoupled, which could be exploited to generate entangled states in
non-interacting systems.Comment: 15 pages, 4 figures, Accepted for publication in Journal of Physics
B, special issue Correlations in light-matter interaction
Self-organized evolution in socio-economic environments
We propose a general scenario to analyze social and economic changes in
modern environments. We illustrate the ideas with a model that incorporating
the main trends is simple enough to extract analytical results and, at the same
time, sufficiently complex to display a rich dynamic behavior. Our study shows
that there exists a macroscopic observable that is maximized in a regime where
the system is critical, in the sense that the distribution of events follow
power-laws. Computer simulations show that, in addition, the system always
self-organizes to achieve the optimal performance in the stationary state.Comment: 4 pages RevTeX; needs epsf.sty and rotate.sty; submitted to Phys Rev
Let
Recommended from our members
Special Economic Zones, Global Value Chains, and the Degree of Economic Linkages in the Dominican Republic
The Dominican Republic is often considered an example of the successful implementation of Special Economic Zones (henceforth SEZs) in the Western hemisphere. The zones fueled economic growth during the 1980s and 1990s and, while they experienced a sharp decline in employment due in part to the expiry of the end of the Multi-Fiber Agreement and stronger international competition in the textile and apparel industry in 2005, signs of recovery have been observed since 2009. Surgical equipment, chemicals and plastics, and footwear have recently emerged as the new drivers of export dynamism in the zones (World Bank, 2015). The objective of this report is to inform the policy discussion around the developmental impact of SEZs in the Dominican Republic by empirically assessing i) the implications of regulatory reforms aimed at complying with WTO disciplines regarding the elimination of incentives conditioned on export performance for SEZs firms, ii) the extent to which SEZs participate in Global Value Chains, and iii) their linkages with domestic suppliers. The report is organized as follows: The second section presents the historical importance of SEZ as an engine of economic growth in the country. The third section depicts the structural shift in terms of production in SEZs and evaluates the degree of value addition taking place in the Dominican Republic. The fourth section evaluates the degree and evolution of linkages between SEZs and local firms. The fifth section shows the impact of the regulatory changes in the SEZ regimen undertaken to comply with WTO disciplines. Finally, some conclusions and policy recommendations are presented in section six
Ediacaran Obduction of a Fore-Arc Ophiolite in SW Iberia: A Turning Point in the Evolving Geodynamic Setting of Peri- Gondwana
The Calzadilla Ophiolite is an ensemble of mafic and ultramafic rocks that represents the
transition between lower crust and upper mantle of a Cadomian (peri-Gondwanan) fore arc. Mapping and
structural analysis of the ophiolite demonstrates that it was obducted in latest Ediacaran times, because the
Ediacaran-Early Cambrian sedimentary series (Malcocinado Formation) discordantly covers it. The ophiolite
and emplacement-related structures are affected by Variscan deformation (Devonian-Carboniferous),
which includes SW verging overturned folds (D1) and thrusts (D2), upright folds (D3), extensional faults (D4),
and later faults (D5). These phases of deformation are explained in the context of Variscan tectonics as the
result of the progressive collision between Gondwana and Laurussia. Qualitative unstraining of Variscan
deformation reveals the primary geometry of Ediacaran-Cambrian structures and uncovers the generation of
east verging thrusts as responsible for the primary obduction of the Calzadilla Ophiolite. Restoration of
planar and linear structures associated with this event indicates an Ediacaran, east directed obduction of the
ophiolite, that is, emplacement of the Cadomian fore arc onto inner sections of the northern margin of
Gondwana. According to regional data, the obduction separates two extension-dominated stages in the
tectonic evolution of the African margin of northern Gondwana preserved in southern Europe. Preobduction
extension brought about the onset and widening of fore-arc and back-arc basins in the external part
of the continent, while postobduction extension facilitated the formation of extensional migmatitic domes,
an oceanward migration of back-arc spreading centers across peri-Gondwana, and the eventual opening
of a major basin such as the Rheic Ocean
Atmospheric Nanoparticles in Photocatalytic and Thermal Production of Atmospheric Pollutants
Atmospheric aerosols which occur above heavily polluted areas such as Mexico City, are characterized and found to be complex materials that have the potential to accelerate important ozone-forming reactions photocatalytically and thermocatalytically. In addition, because the particles are respirable, they may represent a considerable health hazard. The aerosols consist of two intermixed components. The first component consists of amorphous carbonaceous materials of variable composition with fullerene like materials dispersed throughout. The second component is an inorganic material consisting of nanoparticles of oxides and sulfides supported on clay minerals. This inorganic component has all of the characteristics of an airborne photocatalyst.
Nanoparticles of Fe2O3, MnO2 and FeS2 have demonstrated catalytic properties, particularly when they occur in the nanoparticle range, as they do in the subject aerosol materials. These materials have band-gaps that occur in the broad solar spectrum enhancing the photocatalytic adsorption of solar radiation beyond that of the wider band-gap aluminosilicate and titanate materials, which also occur in aerosols. In addition, the materials are acidic and probably are coated with moisture when suspended in air, further enhancing their catalytic ability to crack hydrocarbons and create free radicals
- …