591 research outputs found
Local density approximation for confined bosons in an optical lattice
We investigate local and global properties of the one-dimensional
Bose-Hubbard model with an external confining potential, describing an atomic
condensate in an optical lattice. Using quantum Monte Carlo techniques we
demonstrate that a local-density approximation, which relates the unconfined
and the confined model, yields quantitatively correct results in most of the
interesting parameter range. We also examine claims of universal behavior in
the confined system, and demonstrate the origin of a previously calculated fine
structure in the experimentally accessible momentum distribution.Comment: 7 pages, 11 figures; Section III updated and references adde
Has the Rajiv Aarogyasri Community Health Insurance Scheme of Andhra Pradesh Addressed the Educational Divide in Accessing Health Care?
Correction to ::Optimised isolation method for RNA extraction suitable for RNA sequencing from feline teeth collected in a clinical setting and at post mortem
Transcriptomic profiling of feline teeth highlights the role of matrix metalloproteinase 9 (MMP9) in tooth resorption
Reduction of the sign problem using the meron-cluster approach
The sign problem in quantum Monte Carlo calculations is analyzed using the
meron-cluster solution. The concept of merons can be used to solve the sign
problem for a limited class of models. Here we show that the method can be used
to \textit{reduce} the sign problem in a wider class of models. We investigate
how the meron solution evolves between a point in parameter space where it
eliminates the sign problem and a point where it does not affect the sign
problem at all. In this intermediate regime the merons can be used to reduce
the sign problem. The average sign still decreases exponentially with system
size and inverse temperature but with a different prefactor. The sign exhibits
the slowest decrease in the vicinity of points where the meron-cluster solution
eliminates the sign problem. We have used stochastic series expansion quantum
Monte Carlo combined with the concept of directed loops.Comment: 8 pages, 9 figure
One-dimensional phase transitions in a two-dimensional optical lattice
A phase transition for bosonic atoms in a two-dimensional anisotropic optical
lattice is considered. If the tunnelling rates in two directions are different,
the system can undergo a transition between a two-dimensional superfluid and a
one-dimensional Mott insulating array of strongly coupled tubes. The connection
to other lattice models is exploited in order to better understand the phase
transition. Critical properties are obtained using quantum Monte Carlo
calculations. These critical properties are related to correlation properties
of the bosons and a criterion for commensurate filling is established.Comment: 14 pages, 8 figure
The Best Laid Plans: Access to the Rajiv Aarogyasri community health insurance scheme of Andhra Pradesh
This paper is a qualitative assessment of a public health insurance scheme in the state of Andhra Pradesh, south India, called the Rajiv Aarogyasri Community Health Insurance Scheme (or Aarogyasri), using the case-study method. Focusing on inpatient hospital care and especially on surgical treatments leaves the scheme wanting in meeting the health care needs of and addressing the impoverishing health expenditure incurred by the poor, especially those living in rural areas. Though well-intentioned, people from vulnerable sections of society may find the scheme ultimately unhelpful for their needs. Through an in-depth qualitative approach, the paper highlights not just financial difficulties but also the non-financial barriers to accessing health care, despite the existence of a scheme such as Aarogyasri. Narrative evidence from poor households offers powerful insights into why even the most innovative state health insurance schemes may not achieve their goals and systemic corrections needed to address barriers to health care
Matrix product decomposition and classical simulation of quantum dynamics in the presence of a symmetry
We propose a refined matrix product state representation for many-body
quantum states that are invariant under SU(2) transformations, and indicate how
to extend the time-evolving block decimation (TEBD) algorithm in order to
simulate time evolution in an SU(2) invariant system. The resulting algorithm
is tested in a critical quantum spin chain and shown to be significantly more
efficient than the standard TEBD.Comment: 5 pages, 4 figure
Dynamics and Instabilities of Planar Tensile Cracks in Heterogeneous Media
The dynamics of tensile crack fronts restricted to advance in a plane are
studied. In an ideal linear elastic medium, a propagating mode along the crack
front with a velocity slightly less than the Rayleigh wave velocity, is found
to exist. But the dependence of the effective fracture toughness on
the crack velocity is shown to destabilize the crack front if
. Short wavelength radiation due to weak random
heterogeneities leads to this instability at low velocities. The implications
of these results for the crack dynamics are discussed.Comment: 12 page
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