4,469 research outputs found
Pre-logarithmic and logarithmic fields in a sandpile model
We consider the unoriented two-dimensional Abelian sandpile model on the
half-plane with open and closed boundary conditions, and relate it to the
boundary logarithmic conformal field theory with central charge c=-2. Building
on previous results, we first perform a complementary lattice analysis of the
operator effecting the change of boundary condition between open and closed,
which confirms that this operator is a weight -1/8 boundary primary field,
whose fusion agrees with lattice calculations. We then consider the operators
corresponding to the unit height variable and to a mass insertion at an
isolated site of the upper half plane and compute their one-point functions in
presence of a boundary containing the two kinds of boundary conditions. We show
that the scaling limit of the mass insertion operator is a weight zero
logarithmic field.Comment: 18 pages, 9 figures. v2: minor corrections + added appendi
Hypersonic laminar boundary layers around slender bodies
Compressible laminar boundary layer equations considered for hypersonic flow around slender bodie
Higher Order and boundary Scaling Fields in the Abelian Sandpile Model
The Abelian Sandpile Model (ASM) is a paradigm of self-organized criticality
(SOC) which is related to conformal field theory. The conformal fields
corresponding to some height clusters have been suggested before. Here we
derive the first corrections to such fields, in a field theoretical approach,
when the lattice parameter is non-vanishing and consider them in the presence
of a boundary.Comment: 7 pages, no figure
Quantum critical fluctuations in disordered d-wave superconductors
Quasiparticles in the cuprates appear to be subject to anomalously strong
inelastic damping mechanisms. To explain the phenomenon, Sachdev and
collaborators recently proposed to couple the system to a critically
fluctuating order parameter mode of either id_{xy}- or is-symmetry. Motivated
by the observation that the energies relevant for the dynamics of this mode are
comparable to the scattering rate induced by even moderate impurity
concentrations, we here generalize the approach to the presence of static
disorder. In the id-case, we find that the coupling to disorder renders the
order parameter dynamics diffusive but otherwise leaves much of the
phenomenology observed in the clean case intact. In contrast, the interplay of
impurity scattering and order parameter fluctuations of is-symmetry entails the
formation of a secondary superconductor transition, with a critical temperature
exponentially sensitive to the disorder concentration.Comment: 4 pages, 2 figures include
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In Search of Factors to Online Game Addiction and its Implications
Research has explored online users who are hooked on Internet applications such as chat rooms, web surfing, and interactive games. Online game addiction is one of the problems arisen from the use of the Internet. This study is motivated by a causal connection found from previous research of computer game addiction. The study describes two typical types of online games and looks further into the causes of the addiction by using two main theories. We also propose research hypotheses and discuss possible implications of online game addiction
A selected history of expectation bias in physics
The beliefs of physicists can bias their results towards their expectations
in a number of ways. We survey a variety of historical cases of expectation
bias in observations, experiments, and calculations.Comment: 6 pages, 2 figure
Height variables in the Abelian sandpile model: scaling fields and correlations
We compute the lattice 1-site probabilities, on the upper half-plane, of the
four height variables in the two-dimensional Abelian sandpile model. We find
their exact scaling form when the insertion point is far from the boundary, and
when the boundary is either open or closed. Comparing with the predictions of a
logarithmic conformal theory with central charge c=-2, we find a full
compatibility with the following field assignments: the heights 2, 3 and 4
behave like (an unusual realization of) the logarithmic partner of a primary
field with scaling dimension 2, the primary field itself being associated with
the height 1 variable. Finite size corrections are also computed and
successfully compared with numerical simulations. Relying on these field
assignments, we formulate a conjecture for the scaling form of the lattice
2-point correlations of the height variables on the plane, which remain as yet
unknown. The way conformal invariance is realized in this system points to a
local field theory with c=-2 which is different from the triplet theory.Comment: 68 pages, 17 figures; v2: published version (minor corrections, one
comment added
Boundary conditions and defect lines in the Abelian sandpile model
We add a defect line of dissipation, or crack, to the Abelian sandpile model.
We find that the defect line renormalizes to separate the two-dimensional plane
into two half planes with open boundary conditions. We also show that varying
the amount of dissipation at a boundary of the Abelian sandpile model does not
affect the universality class of the boundary condition. We demonstrate that a
universal coefficient associated with height probabilities near the defect can
be used to classify boundary conditions.Comment: 8 pages, 1 figure; suggestions from referees incorporated; to be
published in Phys. Rev.
Three-leg correlations in the two component spanning tree on the upper half-plane
We present a detailed asymptotic analysis of correlation functions for the
two component spanning tree on the two-dimensional lattice when one component
contains three paths connecting vicinities of two fixed lattice sites at large
distance apart. We extend the known result for correlations on the plane to
the case of the upper half-plane with closed and open boundary conditions. We
found asymptotics of correlations for distance from the boundary to one of
the fixed lattice sites for the cases and .Comment: 16 pages, 5 figure
Partially incoherent optical vortices in self-focusing nonlinear media
We observe stable propagation of spatially localized single- and
double-charge optical vortices in a self-focusing nonlinear medium. The
vortices are created by self-trapping of partially incoherent light carrying a
phase dislocation, and they are stabilized when the spatial incoherence of
light exceeds a certain threshold. We confirm the vortex stabilization effect
by numerical simulations and also show that the similar mechanism of
stabilization applies to higher-order vortices.Comment: 4 pages and 6 figures (including 3 experimental figures
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