8,643 research outputs found
A Tutorial on Estimating Time-Varying Vector Autoregressive Models
Time series of individual subjects have become a common data type in
psychological research. These data allow one to estimate models of
within-subject dynamics, and thereby avoid the notorious problem of making
within-subjects inferences from between-subjects data, and naturally address
heterogeneity between subjects. A popular model for these data is the Vector
Autoregressive (VAR) model, in which each variable is predicted as a linear
function of all variables at previous time points. A key assumption of this
model is that its parameters are constant (or stationary) across time. However,
in many areas of psychological research time-varying parameters are plausible
or even the subject of study. In this tutorial paper, we introduce methods to
estimate time-varying VAR models based on splines and kernel-smoothing
with/without regularization. We use simulations to evaluate the relative
performance of all methods in scenarios typical in applied research, and
discuss their strengths and weaknesses. Finally, we provide a step-by-step
tutorial showing how to apply the discussed methods to an openly available time
series of mood-related measurements
Cavity state preparation using adiabatic transfer
We show how to prepare a variety of cavity field states for multiple
cavities. The state preparation technique used is related to the method of
stimulated adiabatic Raman passage or STIRAP. The cavity modes are coupled by
atoms, making it possible to transfer an arbitrary cavity field state from one
cavity to another, and also to prepare non-trivial cavity field states. In
particular, we show how to prepare entangled states of two or more cavities,
such as an EPR state and a W state, as well as various entangled superpositions
of coherent states in different cavities, including Schrodinger cat states. The
theoretical considerations are supported by numerical simulations.Comment: 11 pages, 9 figures. Accepted in Phys. Rev.
Effects of the Nitric Oxide Synthease Inhibitor NG-nitro-L-arginine on the Erectile Response to Cavernous Nerve Stimulation in the Rabbit
Quantum phase transitions in disordered dimerized quantum spin models and the Harris criterion
We use quantum Monte Carlo simulations to study effects of disorder on the
quantum phase transition occurring versus the ratio g=J/J' in square-lattice
dimerized S=1/2 Heisenberg antiferromagnets with intra- and inter-dimer
couplings J and J'. The dimers are either randomly distributed (as in the
classical dimer model), or come in parallel pairs with horizontal or vertical
orientation. In both cases the transition violates the Harris criterion,
according to which the correlation-length exponent should satisfy nu >= 1. We
do not detect any deviations from the three-dimensional O(3) universality class
obtaining in the absence of disorder (where nu = 0.71). We discuss special
circumstances which allow nu<1 for the type of disorder considered here.Comment: 4+ pages, 3 figure
The probability density function tail of the Kardar-Parisi-Zhang equation in the strongly non-linear regime
An analytical derivation of the probability density function (PDF) tail
describing the strongly correlated interface growth governed by the nonlinear
Kardar-Parisi-Zhang equation is provided. The PDF tail exactly coincides with a
Tracy-Widom distribution i.e. a PDF tail proportional to , where is the the width of the interface. The PDF tail is
computed by the instanton method in the strongly non-linear regime within the
Martin-Siggia-Rose framework using a careful treatment of the non-linear
interactions. In addition, the effect of spatial dimensions on the PDF tail
scaling is discussed. This gives a novel approach to understand the rightmost
PDF tail of the interface width distribution and the analysis suggests that
there is no upper critical dimension.Comment: 17 pages, 2 figure
Intracavernous Calcitonin-gene Related Peptide Plus Prostaglandin E 1. Possible Alternative to Penile Implants in Selected Patients.
Stereoscopic wide field of view imaging system
A stereoscopic imaging system incorporates a plurality of imaging devices or cameras to generate a high resolution, wide field of view image database from which images can be combined in real time to provide wide field of view or panoramic or omni-directional still or video images
Spectrum of Andreev Bound States in a Molecule Embedded Inside a Microwave-Excited Superconducting Junction
Non-dissipative Josephson current through nanoscale superconducting
constrictions is carried by spectroscopically sharp energy states, so-called
Andreev bound states. Although theoretically predicted almost 40 years ago, no
direct spectroscopic evidence of these Andreev bound states exists to date. We
propose a novel type of spectroscopy based on embedding a superconducting
constriction, formed by a single-level molecule junction, in a microwave QED
cavity environment. In the electron-dressed cavity spectrum we find a polariton
excitation at twice the Andreev bound state energy, and a superconducting-phase
dependent ac Stark shift of the cavity frequency. Dispersive measurement of
this frequency shift can be used for Andreev bound state spectroscopy.Comment: Published version; 4+ pages, 3 figure
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