2,673 research outputs found
Thermodynamic formalism for dissipative quantum walks
We consider the dynamical properties of dissipative continuous-time quantum
walks on directed graphs. Using a large-deviation approach we construct a
thermodynamic formalism allowing us to define a dynamical order parameter, and
to identify transitions between dynamical regimes. For a particular class of
dissipative quantum walks we propose a quantum generalization of the the
classical PageRank vector, used to rank the importance of nodes in a directed
graph. We also provide an example where one can characterize the dynamical
transition from an effective classical random walk to a dissipative quantum
walk as a thermodynamic crossover between distinct dynamical regimes.Comment: 8 page
Statistical properties of random matrix product states
We study the set of random matrix product states (RMPS) introduced in
arXiv:0908.3877 as a tool to explore foundational aspects of quantum
statistical mechanics. In the present work, we provide an accurate numerical
and analytical investigation of the properties of RMPS. We calculate the
average state of the ensemble in the non-homogeneous case, and numerically
check the validity of this result. We also suggest using RMPS as a tool to
approximate properties of general quantum random states. The numerical
simulations presented here support the accuracy and efficiency of this
approximation. These results suggest that any generalized canonical state can
be approximated with high probability by the reduced density matrix of a random
MPS, if the average MPS coincide with the associated microcanonical ensemble.Comment: 12 pages, 17 figures; published versio
Spin networks, quantum automata and link invariants
The spin network simulator model represents a bridge between (generalized)
circuit schemes for standard quantum computation and approaches based on
notions from Topological Quantum Field Theories (TQFT). More precisely, when
working with purely discrete unitary gates, the simulator is naturally modelled
as families of quantum automata which in turn represent discrete versions of
topological quantum computation models. Such a quantum combinatorial scheme,
which essentially encodes SU(2) Racah--Wigner algebra and its braided
counterpart, is particularly suitable to address problems in topology and group
theory and we discuss here a finite states--quantum automaton able to accept
the language of braid group in view of applications to the problem of
estimating link polynomials in Chern--Simons field theory.Comment: LateX,19 pages; to appear in the Proc. of "Constrained Dynamics and
Quantum Gravity (QG05), Cala Gonone (Italy) September 12-16 200
First-order transitions for some generalized XY models
In this note we demonstrate the occurrence of first-order transitions in
temperature for some recently introduced generalized XY models, and also point
out the connection between them and annealed site-diluted (lattice-gas)
continuous-spin models
LIFE JOURNEY WITH SOMEBODY SPECIAL: THE HIGHS AND LOWS OF PARENTS OF CHILDREN WITH DISABILITY
Central to this study is the lived experiences of parents of children with physical disability. This study was conducted at Barangay Poblacion 8, Midsayap, Cotabato. It included as participants purposively chosen parents of children with physical disability. Their ages ranged from 31 to 53 years old, and were all mothers. The physical disabilities of their children were either musculoskeletal (orthopaedic) or visual. This study made use of the phenomenological research design. Findings bared that despite the apparent conditions of their children, the participants joyfully and with gratitude accepted their children as blessings from God. They spent bonding moments with them, and at times appreciative of their learning of new things, and were busy taking good care of the total well-being of their children. They were aware of their childrenâs limitations, but they do not consider them as different. Nevertheless, they sought acceptance, respect, and understanding from others. The participants were concerned about the health issues of their children, anxious about the mistreatment they received from others, and pondered on their possible rejection in the future. The participants stood by their children and draw strength from God. They look at the bright side of life and hope that their children finish studying. The participants as mothers were longing for help for their childrenâs sake. Article visualizations
Relativistic MHD Simulations of Jets with Toroidal Magnetic Fields
This paper presents an application of the recent relativistic HLLC
approximate Riemann solver by Mignone & Bodo to magnetized flows with vanishing
normal component of the magnetic field.
The numerical scheme is validated in two dimensions by investigating the
propagation of axisymmetric jets with toroidal magnetic fields.
The selected jet models show that the HLLC solver yields sharper resolution
of contact and shear waves and better convergence properties over the
traditional HLL approach.Comment: 12 pages, 5 figure
Solar Wind at 6.8 Solar Radii from UVCS Observation of Comet C/1996Y1
The comet C/1996Y1, a member of the Kreutz family of Sun-grazing comets, was observed with the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO) satellite. The Lyα line profile and spatial distribution are interpreted in terms of the theory of bow shocks driven by mass-loading. At the time of the observation, the comet was 6.8 Râ from the Sun in a region of high-speed wind, a region difficult to observe directly with the SOHO instruments but an important region for testing models of solar wind acceleration and heating. We find a solar wind speed below 640 km s-1 and a constraint on the combination of solar wind speed and proton temperature. The total energy per proton at 6.8 Râ is 50%-75% of the energy at 1 AU, indicating that significant heating occurs at larger radii. The centroid and width of the Lyα line generally confirm the predictions of models of the cometary bow shock driven by mass-loading as cometary molecules are ionized and swept up in the solar wind. We estimate an outgassing rate of 20 kg s-1, which implies an active area of the nucleus only about 6.7 m in diameter at 6.8 Râ. This is likely to be the size of the nucleus, because any inert mantle would have probably been blown off during the approach to the Sun
Band dispersion in the deep 1s core level of graphene
Chemical bonding in molecules and solids arises from the overlap of valence
electron wave functions, forming extended molecular orbitals and dispersing
Bloch states, respectively. Core electrons with high binding energies, on the
other hand, are localized to their respective atoms and their wave functions do
not overlap significantly. Here we report the observation of band formation and
considerable dispersion (up to 60 meV) in the core level of the carbon
atoms forming graphene, despite the high C binding energy of 284
eV. Due to a Young's double slit-like interference effect, a situation arises
in which only the bonding or only the anti-bonding states is observed for a
given photoemission geometry.Comment: 12 pages, 3 figures, including supplementary materia
Deep Chandra observations of the stripped galaxy group falling into Abell 2142
In the local Universe, the growth of massive galaxy clusters mainly operates through the continuous accretion of group-scale systems. The infalling group in Abell 2142 is the poster child of such an accreting group, and as such, it is an ideal target to study the astrophysical processes induced by structure formation. We present the results of a deep (200 ks) observation of this structure with Chandra that highlights the complexity of this system in exquisite detail. In the core of the group, the spatial resolution of Chandra reveals a leading edge and complex AGN-induced activity. The morphology of the stripped gas tail appears straight in the innermost 250 kpc, suggesting that magnetic draping efficiently shields the gas from its surroundings. However, beyond ~ 300 kpc from the core, the tail flares and the morphology becomes strongly irregular, which could be explained by a breaking of the drape, for example, caused by turbulent motions. The power spectrum of surface-brightness fluctuations is relatively flat (P2D â kâ»ÂČâÂł which indicates that thermal conduction is strongly inhibited even beyond the region where magnetic draping is effective. The amplitude of density fluctuations in the tail is consistent with a mild level of turbulence with a Mach number M3D ~ 0:1 -0:25. Overall, our results show that the processes leading to the thermalization and mixing of the infalling gas are slow and relatively inefficient
Numerical models of irrotational binary neutron stars in general relativity
We report on general relativistic calculations of quasiequilibrium
configurations of binary neutron stars in circular orbits with zero vorticity.
These configurations are expected to represent realistic situations as opposed
to corotating configurations. The Einstein equations are solved under the
assumption of a conformally flat spatial 3-metric (Wilson-Mathews
approximation). The velocity field inside the stars is computed by solving an
elliptical equation for the velocity scalar potential. Results are presented
for sequences of constant baryon number (evolutionary sequences). Although the
central density decreases much less with the binary separation than in the
corotating case, it still decreases. Thus, no tendency is found for the stars
to individually collapse to black hole prior to merger.Comment: Minor corrections, improved figure, 5 pages, REVTeX, Phys. Rev. Lett.
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