5,586 research outputs found
Competing Universalities in Kardar-Parisi-Zhang (KPZ) Growth Models
We report on the universality of height fluctuations at the crossing point of
two interacting (1+1)-dimensional Kardar-Parisi-Zhang (KPZ) interfaces with
curved and flat initial conditions. We introduce a control parameter p as the
probability for the initially flat geometry to be chosen and compute the phase
diagram as a function of p. We find that the distribution of the fluctuations
converges to the Gaussian orthogonal ensemble Tracy-Widom (TW) distribution for
p0.5. For
p=0.5 where the two geometries are equally weighted, the behavior is governed
by an emergent Gaussian statistics in the universality class of Brownian
motion. We propose a phenomenological theory to explain our findings and
discuss possible applications in nonequilibrium transport and traffic flow.Comment: 5 pages, 6 figures, Phys. Rev. Lett. (2019) (accepted
An exactly solvable record model for rainfall
Daily precipitation time series are composed of null entries corresponding to
dry days and nonzero entries that describe the rainfall amounts on wet days.
Assuming that wet days follow a Bernoulli process with success probability ,
we show that the presence of dry days induces negative correlations between
record-breaking precipitation events. The resulting non-monotonic behavior of
the Fano factor of the record counting process is recovered in empirical data.
We derive the full probability distribution of the number of records
up to time , and show that for large , its large deviation form
coincides with that of a Poisson distribution with parameter . We
also study in detail the joint limit , , which yields a
random record model in continuous time .Comment: 11 pages, 2 figures + 13 pages and 2 figures of supplemental materia
Spin correlation functions in random-exchange s=1/2 XXZ chains
The decay of (disorder-averaged) static spin correlation functions at T=0 for
the one-dimensional spin-1/2 XXZ antiferromagnet with uniform longitudinal
coupling and random transverse coupling is investigated
by numerical calculations for ensembles of finite chains. At (XX
model) the calculation is based on the Jordan-Wigner mapping to free lattice
fermions for chains with up to N=100 sites. At Lanczos
diagonalizations are carried out for chains with up to N=22 sites. The
longitudinal correlation function is found to exhibit a
power-law decay with an exponent that varies with $\Delta$ and, for nonzero
$\Delta$, also with the width of the $\lambda_i$-distribution. The results for
the transverse correlation function show a crossover from
power-law decay to exponential decay as the exchange disorder is turned on.Comment: RevTex manuscript (7 pages), 4 postscript figure
X-Rays from the Nearby Solitary Millisecond Pulsar PSR J0030+0451 - the Final ROSAT Observations
We report on X-ray observations of the solitary 4.8 ms pulsar PSR J0030+0451.
The pulsar was one of the last targets observed in DEC-98 by the ROSAT PSPC.
X-ray pulses are detected on a level and make the source the
millisecond pulsar detected in the X-ray domain. The pulsed fraction
is found to be . The X-ray pulse profile is characterized by two
narrow peaks which match the gross pulse profile observed at 1.4 GHz. Assuming
a Crab-like spectrum the X-ray flux is in the range
erg s cm ( keV), implying an X-ray efficiency of
.Comment: Accepted for publication in Ap
Decay of superfluid currents in the interacting one-dimensional Bose gas
We examine the superfluid properties of a 1D Bose gas in a ring trap based on
the model of Lieb and Liniger. While the 1D Bose gas has nonclassical
rotational inertia and exhibits quantization of velocities, the metastability
of currents depends sensitively on the strength of interactions in the gas: the
stronger the interactions, the faster the current decays. It is shown that the
Landau critical velocity is zero in the thermodynamic limit due to the first
supercurrent state, which has zero energy and finite probability of excitation.
We calculate the energy dissipation rate of ring currents in the presence of
weak defects, which should be observable on experimental time scales.Comment: 5 pages, 4 figure
First Evaluation of an Index of Low Vagally-Mediated Heart Rate Variability as a Marker of Health Risks in Human Adults: Proof of Concept.
Multiple studies have demonstrated low vagally-mediated heart rate variability (HRV) being associated with a range of risk factors for heart disease and stroke, including inflammation, hyperglycemia, hyperlipidemia, and hypertension. Yet, no cut point exists that indicates elevated risk. In the present study we sought to identify a cut point-value for HRV that is associated with elevated risk across a range of known risk factors. METHODS:A total of 9550 working adults from 19 study sites took part in a health assessment that included measures of inflammation, hyperglycemia, hyperlipidemia, and hypertension and vagally-mediated HRV (Root mean square of successive differences between normal heartbeats (RMSSD)). Multiple age and sex adjusted logistic regressions were calculated per risk factor (normal versus clinical range), with RMSSD being entered in binary at different cut points ranging from 15-39 msec with a 2 msec increment. RESULTS:For daytime RMSSD, values below 25 ± 4 indicated elevated risk (odds ratios (OR) 1.5-3.5 across risk factors). For nighttime RMSSD, values below 29 ± 4 indicated elevated risk (OR 1.2-2.0). CONCLUSION:These results provide the first evidence that a single value of RMSSD may be associated with elevated risk across a range of established cardiovascular risk factors and may present an easy to assess novel marker of cardiovascular risk
Dissipation in a rotating frame: master equation, effective temperature and Lamb-shift
Motivated by recent realizations of microwave-driven nonlinear resonators in
superconducting circuits, the impact of environmental degrees of freedom is
analyzed as seen from a rotating frame. A system plus reservoir model is
applied to consistently derive in the weak coupling limit the master equation
for the reduced density in the moving frame and near the first bifurcation
threshold. It turns out that additional interactions between momenta of system
and bath appear which have been omitted in previous studies. Explicit
expressions for the effective temperature and the Lamb-shift are given which
for ohmic baths are in agreement with experimental findings, while for
structured environments population inversion is predicted that may
qualitatively explain recent observations.Comment: 7 pages, 5 figure
Does Chilenia exist? : Evidence from the evolution of collisional and coastal accretionary systems between the latitudes 30° S and 35° S
Application of the disposition model to breast cancer data
In this paper, we have presented the second level nesting of Bonney's disposition model (Bonney, 1998) and examined the implications of higher level nesting of the disposition model in relation to the dimension of the parameter space. We have also compared the performance of the disposition model with Cox's regression model (Cox, 1972). It has been observed that the disposition model has a very large number of unknown parameters, and is therefore limited by the method of estimation used. In the case of the maximum likelihood method, reasonable estimates are obtained if the number of parameters in the model is at most nine. This corresponds to about four to seven covariates. Since each covariate in Cox's model provides a parameter, it is possible to include more covariates in the regression analysis. On the other hand, as opposed to Cox's model, the disposition model is fitted with parameters to capture aggregation in families, if there should be any. The choice of a particular model should therefore depend on the available data set and the purpose of the statistical analysis. --Second level nesting,Proportional hazards model,Quadratic exponential form,Partial likelihood,Familial aggregation,Second-order methods,Marginal models,Conditional models
Enhanced binding and cold compression of nuclei due to admixture of antibaryons
We discuss the possibility of producing a new kind of nuclear system by putting a few antibaryons inside ordinary nuclei. The structure of such systems is calculated within the relativistic mean field model assuming that the nucleon and antinucleon potentials are related by the G parity transformation. The presence of antinucleons leads to decreasing vector potential and increasing scalar potential for the nucleons. As a result, a strongly bound system of high density is formed. Due to the significant reduction of the available phase space the annihilation probability might be strongly suppressed in such systems
- …