20,081 research outputs found
Learning and Communication in Sender-Reciever Games: An Economic Investigation
This paper compares the performance of stimulus response (SR) and belief-based learning (BBL) using data from game theory experiments. The environment, extensive form games played in a population setting, is novel in the empirical literature on learning in games. Both the SR and BBL models fit the data reasonably well in common interest games with history while the test results accept SR and reject BBL in games with no history and in all but one of the divergent interest games. Estimation is challenging since the likelihood function is not globally concave and the results may be subject to convergence bias.econometrics;game theory and experiments
Classical Correlations and Entanglement in Quantum Measurements
We analyze a quantum measurement where the apparatus is initially in a mixed
state. We show that the amount of information gained in a measurement is not
equal to the amount of entanglement between the system and the apparatus, but
is instead equal to the degree of classical correlations between the two. As a
consequence, we derive an uncertainty-like expression relating the information
gain in the measurement and the initial mixedness of the apparatus. Final
entanglement between the environment and the apparatus is also shown to be
relevant for the efficiency of the measurement.Comment: to appear in Physical Review Letter
First-principles phase diagram calculations for the HfC–TiC, ZrC–TiC, and HfC–ZrC solid solutions
We report first-principles phase diagram calculations for the binary systems HfC–TiC, TiC–ZrC, and HfC–ZrC. Formation energies for superstructures of various bulk compositions were computed with a plane-wave pseudopotential method. They in turn were used as a basis for fitting cluster expansion Hamiltonians, both with and without approximations for excess vibrational free energies. Significant miscibility gaps are predicted for the systems TiC–ZrC and HfC–TiC, with consolute temperatures in excess of 2000 K. The HfC–ZrC system is predicted to be completely miscibile down to 185 K. Reductions in consolute temperature due to excess vibrational free energy are estimated to be ~7%, ~20%, and ~0%, for HfC–TiC, TiC–ZrC, and HfC–ZrC, respectively. Predicted miscibility gaps are symmetric for HfC–ZrC, almost symmetric for HfC–TiC and asymmetric for TiC–ZrC
3C 295, a cluster and its cooling flow at z=0.46
We present ROSAT HRI data of the distant and X-ray luminous (L_x(bol)=2.6^
{+0.4}_{-0.2} 10^{45}erg/sec) cluster of galaxies 3C 295. We fit both a
one-dimensional and a two-dimensional isothermal beta-model to the data, the
latter one taking into account the effects of the point spread function (PSF).
For the error analysis of the parameters of the two-dimensional model we
introduce a Monte-Carlo technique. Applying a substructure analysis, by
subtracting a cluster model from the data, we find no evidence for a merger,
but we see a decrement in emission South-East of the center of the cluster,
which might be due to absorption. We confirm previous results by Henry &
Henriksen(1986) that 3C 295 hosts a cooling flow. The equations for the simple
and idealized cooling flow analysis presented here are solely based on the
isothermal beta-model, which fits the data very well, including the center of
the cluster. We determine a cooling flow radius of 60-120kpc and mass accretion
rates of dot{M}=400-900 Msun/y, depending on the applied model and temperature
profile. We also investigate the effects of the ROSAT PSF on our estimate of
dot{M}, which tends to lead to a small overestimate of this quantity if not
taken into account. This increase of dot{M} (10-25%) can be explained by a
shallower gravitational potential inferred by the broader overall profile
caused by the PSF, which diminishes the efficiency of mass accretion. We also
determine the total mass of the cluster using the hydrostatic approach. At a
radius of 2.1 Mpc, we estimate the total mass of the cluster (M{tot}) to be
(9.2 +/- 2.7) 10^{14}Msun. For the gas to total mass ratio we get M{gas}/M{tot}
=0.17-0.31, in very good agreement with the results for other clusters of
galaxies, giving strong evidence for a low density universe.Comment: 26 pages, 7 figures, accepted for publication in Ap
Wave Function Collapse in a Mesoscopic Device
We determine the non-local in time and space current-current cross correlator
in a mesoscopic conductor with a
scattering center at the origin. Its excess part appearing at finite voltage
exhibits a unique dependence on the retarded variable , with the Fermi
velocity. The non-monotonic dependence of the retardation on and its
absence at the symmetric position is a signature of the wave
function collapse, which thus becomes amenable to observation in a mesoscopic
solid state device.Comment: 7 pages, 2 fugure
Passage-time distributions from a spin-boson detector model
The passage-time distribution for a spread-out quantum particle to traverse a
specific region is calculated using a detailed quantum model for the detector
involved. That model, developed and investigated in earlier works, is based on
the detected particle's enhancement of the coupling between a collection of
spins (in a metastable state) and their environment. We treat the continuum
limit of the model, under the assumption of the Markov property, and calculate
the particle state immediately after the first detection. An explicit example
with 15 boson modes shows excellent agreement between the discrete model and
the continuum limit. Analytical expressions for the passage-time distribution
as well as numerical examples are presented. The precision of the measurement
scheme is estimated and its optimization discussed. For slow particles, the
precision goes like , which improves previous estimates,
obtained with a quantum clock model.Comment: 11 pages, 6 figures; minor changes, references corrected; accepted
for publication in Phys. Rev.
Field-induced transition from parallel to perpendicular parametric pumping for a microstrip transducer
Microstrip transducers used for the excitation of spin waves in magnetic
films possess two characteristic properties: high spatial localization of the
microwave magnetic field and the presence of field components parallel and
perpendicular to the bias field.
Here, the effects of these features on the process of parametric pumping are
presented. By microwave measurements of the spin-wave instability threshold a
transition from parallel pumping to perpendicular pumping at the critical field
with the minimal threshold is observed. This transition is
accompanied by a sharp threshold increase above the critical field due to the
spatial confinement of the pump region.Comment: 4 pages, 2 figure
Supernova Inelastic Neutrino-Nucleus Cross Sections from High-Resolution Electron Scattering Experiments and Shell-Model Calculations
Highly precise data on the magnetic dipole strength distributions from the
Darmstadt electron linear accelerator for the nuclei 50Ti, 52Cr and 54Fe are
dominated by isovector Gamow-Teller-like contributions and can therefore be
translated into inelastic total and differential neutral-current
neutrino-nucleus cross sections at supernova neutrino energies. The results
agree well with large-scale shell-model calculations, validating this model.Comment: 5 pages, 4 figures, RevTeX 4, version accepted in Phys. Rev. Letter
Diffusion Processes: entropy, Gibbs states and the continuous time Ruelle operator
We consider a Riemmaniann compact manifold , the associated Laplacian
and the corresponding Brownian motion , Given a
Lipschitz function we consider the operator
, which acts on differentiable functions via the operator
for all .
Denote by , the semigroup acting on functions given by
We will show that this semigroup is a continuous-time version of the
discrete-time Ruelle operator.
Consider the positive differentiable eigenfunction
associated to the main eigenvalue for the semigroup , . From the function , in a procedure similar to the one used in the case
of discrete-time Thermodynamic Formalism, we can associate via a coboundary
procedure a certain stationary Markov semigroup. The probability on the
Skhorohod space obtained from this new stationary Markov semigroup can be seen
as a stationary Gibbs state associated with the potential . We define
entropy, pressure, the continuous-time Ruelle operator and we present a
variational principle of pressure for such a setting
Local Unitary Quantum Cellular Automata
In this paper we present a quantization of Cellular Automata. Our formalism
is based on a lattice of qudits, and an update rule consisting of local unitary
operators that commute with their own lattice translations. One purpose of this
model is to act as a theoretical model of quantum computation, similar to the
quantum circuit model. It is also shown to be an appropriate abstraction for
space-homogeneous quantum phenomena, such as quantum lattice gases, spin chains
and others. Some results that show the benefits of basing the model on local
unitary operators are shown: universality, strong connections to the circuit
model, simple implementation on quantum hardware, and a wealth of applications.Comment: To appear in Physical Review
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