786 research outputs found
Generalized Opinion Dynamics from Local Optimization Rules
We study generalizations of the Hegselmann-Krause (HK) model for opinion
dynamics, incorporating features and parameters that are natural components of
observed social systems. The first generalization is one where the strength of
influence depends on the distance of the agents' opinions. Under this setup, we
identify conditions under which the opinions converge in finite time, and
provide a qualitative characterization of the equilibrium. We interpret the HK
model opinion update rule as a quadratic cost-minimization rule. This enables a
second generalization: a family of update rules which possess different
equilibrium properties. Subsequently, we investigate models in which a external
force can behave strategically to modulate/influence user updates. We consider
cases where this external force can introduce additional agents and cases where
they can modify the cost structures for other agents. We describe and analyze
some strategies through which such modulation may be possible in an
order-optimal manner. Our simulations demonstrate that generalized dynamics
differ qualitatively and quantitatively from traditional HK dynamics.Comment: 20 pages, under revie
Entanglement measurement with discrete multiple coin quantum walks
Within a special multi-coin quantum walk scheme we analyze the effect of the
entanglement of the initial coin state. For states with a special entanglement
structure it is shown that this entanglement can be meausured with the mean
value of the walk, which depends on the i-concurrence of the initial coin
state. Further on the entanglement evolution is investigated and it is shown
that the symmetry of the probability distribution is reflected by the symmetry
of the entanglement distribution.Comment: 9 pages, IOP styl
Doped Mott Insulators in the Triangular Lattice Hubbard Model
We investigate the evolution of the Mott insulators in the triangular lattice
Hubbard Model, as a function of hole doping in both the strong and
intermediate coupling limit. Using the density matrix renormalization group
(DMRG) method, at light hole doping , we find a
significant difference between strong and intermediate couplings. Notably, at
intermediate coupling an unusual metallic state emerges, with short ranged spin
correlations but long ranged spin-chirality order. Moreover, no clear Fermi
surface or wave-vector is observed. These features disappear on increasing
interaction strength or on further doping. At strong coupling, the 120 degree
magnetic order of the insulating magnet persists for light doping, and produces
hole pockets with a well defined Fermi surface. On further doping, SDW order and coherent hole Fermi pockets are found at
both strong and intermediate coupling. At even higher doping , the SDW order is suppressed and the spin-singlet Cooper pair
correlations are simultaneously enhanced. We interpret this as the onset of
superconductivity on suppressing magnetic order. We also briefly comment on the
strong particle hole asymmetry of the model, and contrast electron versus hole
doping.Comment: 9 pages, 11 figure
Prospective study on prescribing pattern of antihypertensive drugs at a tertiary care hospital
Background: Hypertension is the leading non-communicable disease risk attributing to cardio vascular morbidity and mortality. Various reasons are socio-economic, behavioural, sedentary life style, nutritional, age, obesity and poor health maintenance. A wide range of antihypertensive drugs belonging to different pharmacological classes are available alone or in combinations. Present study was done to evaluate the prescribing pattern of antihypertensive drugs at a tertiary care hospital.Methods: A prospective, observational, non-interventional, hospital-based study was carried out in hypertensive patients attending outpatient department of General Medicine at Medical College Hospital attached to Vijayanagar Institute of Medical Sciences, Ballari. Data was collected from outpatient slip of patients in a predesigned case record form, which was analysed using descriptive statistics.Results: Among 200 patients analysed 95 (47.5%) were males and 105 (52.5%) were females, with maximum number of patients falling in the age group 61-70years. Among antihypertensives prescribed, amlodipine (78.5%) was most frequently prescribed drug. Frequently used drugs for monotherapy - amlodipine (37.5%), for two drug therapy - amlodipine + atenolol (25.5%), and for three drug therapy - amlodipine + atenolol + telmisartan (2.5%). WHO prescribing indicators: Average number of drugs per encounter is 2.38 (±1.19). Percentage of drugs prescribed by generic name is 76.47%. Percentage of drugs prescribed from essential drug list is 97.89%.Conclusions: Present study shows current trends in prescription of antihypertensives in tertiary care hospital and their rational use. Study emphasizes need for preventive and educative measures about hypertension in population
Prediction of Toric Code Topological Order from Rydberg Blockade
The physical realization of topological order as encountered in
the paradigmatic toric code has proven to be an elusive goal. We predict that
this phase of matter can be realized in a two-dimensional array of Rydberg
atoms placed on the ruby lattice, at specific values of the Rydberg blockade
radius. First, we show that the blockade model -- also known as a 'PXP' model
-- realizes a monomer-dimer model on the kagome lattice with a single-site
kinetic term. This can be interpreted as a gauge theory whose
dynamics is generated by monomer fluctuations. We obtain its phase diagram
using the numerical density matrix renormalization group method and find a
topological quantum liquid (TQL) as evidenced by multiple measures including
(i) a continuous transition between two featureless phases, (ii) a topological
entanglement entropy of as measured in various geometries, (iii)
degenerate topological ground states and (iv) the expected modular matrix from
ground state overlap. Next, we show that the TQL persists upon including
realistic, algebraically-decaying van der Waals interactions
for a choice of lattice parameters. Moreover, we can directly access
topological loop operators, including the Bricmont-Fr\"ohlich-Fredenhagen-Marcu
order parameter. We show how these can be measured experimentally using a
dynamic protocol, providing a "smoking gun" experimental signature of the TQL
phase. Finally, we show how to trap an emergent anyon and realize different
topological boundary conditions, and we discuss the implications for exploring
fault-tolerant quantum memories.Comment: Updates include a confirmation that the spin liquid on a ruby lattice
(for choice of lattice parameter rho=3) persists upon including long-range
Van der Waals interaction
Two dimensional anisotropic non Fermi-liquid phase of coupled Luttinger liquids
We show using bosonization techniques, that strong forward scattering
interactions between one dimensional spinless Luttinger liquids (LL) can
stabilize a phase where charge-density wave, superconducting and transverse
single particle hopping perturbations are irrelevant. This new phase retains
its LL like properties in the directions of the chains, but with relations
between exponents modified by the transverse interactions, whereas, it is a
perfect insulator in the transverse direction. The mechanism that stabilizes
this phase are strong transverse charge density wave fluctuations at
incommensurate wavevector, which frustrates crystal formation by preventing
lock-in of the in-chain density waves.Comment: (4 pages, 2 figures
Supersolid Order from Disorder: Hard-Core Bosons on the Triangular Lattice
We study the interplay of Mott localization, geometric frustration, and
superfluidity for hard-core bosons with nearest-neighbor repulsion on the
triangular lattice. For this model at half-filling, we demonstrate that
superfluidity survives for arbitrarily large repulsion, and that diagonal solid
order emerges in the strongly correlated regime from an order-by-disorder
mechanism. This is thus an unusual example of a stable supersolid phase of
hard-core lattice bosons at a commensurate filling.Comment: 4 pages, 2 figures; finite-size scaling discussion adde
Anomalous Aharonov-Bohm conductance oscillations from topological insulator surface states
We study transport properties of a topological insulator nanowire when a
magnetic field is applied along its length. We predict that with strong surface
disorder, a characteristic signature of the band topology is revealed in
Aharonov Bohm (AB) oscillations of the conductance. These oscillations have a
component with anomalous period , and with conductance maxima at
odd multiples of , i.e. when the AB phase for surface electrons
is . This is intimately connected to the band topology and a surface
curvature induced Berry phase, special to topological insulator surfaces. We
discuss similarities and differences from recent experiments on BiSe
nanoribbons, and optimal conditions for observing this effect.Comment: 7 pages, 2 figure
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