4,601 research outputs found
Revisiting Entropy Rate Constancy in Text
The uniform information density (UID) hypothesis states that humans tend to
distribute information roughly evenly across an utterance or discourse. Early
evidence in support of the UID hypothesis came from Genzel & Charniak (2002),
which proposed an entropy rate constancy principle based on the probability of
English text under n-gram language models. We re-evaluate the claims of Genzel
& Charniak (2002) with neural language models, failing to find clear evidence
in support of entropy rate constancy. We conduct a range of experiments across
datasets, model sizes, and languages and discuss implications for the uniform
information density hypothesis and linguistic theories of efficient
communication more broadly.Comment: Findings of EMNLP 202
Chemical freeze-out in relativistic heavy-ion collisions
One surprising result in relativistic heavy-ion collisions is that the
abundance of various particles measured in experiments is consistent with the
picture that they reach chemical equilibrium at a temperature much higher than
the temperature they freeze out kinetically. Using a multiphase transport model
to study particle production in these collisions, we find that the above result
is due to the constancy of the entropy per particle during the evolution of the
hadronic matter from the chemical to the kinetic freeze-out. We further use a
hadron resonance gas model to illustrate the result from the transport model
study.Comment: 5 pages, 4 figure
Collision-dependent power law scalings in 2D gyrokinetic turbulence
Nonlinear gyrokinetics provides a suitable framework to describe
short-wavelength turbulence in magnetized laboratory and astrophysical plasmas.
In the electrostatic limit, this system is known to exhibit a free energy
cascade towards small scales in (perpendicular) real and/or velocity space. The
dissipation of free energy is always due to collisions (no matter how weak the
collisionality), but may be spread out across a wide range of scales. Here, we
focus on freely-decaying 2D electrostatic turbulence on sub-ion-gyroradius
scales. An existing scaling theory for the turbulent cascade in the weakly
collisional limit is generalized to the moderately collisional regime. In this
context, non-universal power law scalings due to multiscale dissipation are
predicted, and this prediction is confirmed by means of direct numerical
simulations.Comment: 7 pages, 5 figures, accepted for publication in Physics of Plasma
Configuration Complexities of Hydrogenic Atoms
The Fisher-Shannon and Cramer-Rao information measures, and the LMC-like or
shape complexity (i.e., the disequilibrium times the Shannon entropic power) of
hydrogenic stationary states are investigated in both position and momentum
spaces. First, it is shown that not only the Fisher information and the
variance (then, the Cramer-Rao measure) but also the disequilibrium associated
to the quantum-mechanical probability density can be explicitly expressed in
terms of the three quantum numbers (n, l, m) of the corresponding state.
Second, the three composite measures mentioned above are analytically,
numerically and physically discussed for both ground and excited states. It is
observed, in particular, that these configuration complexities do not depend on
the nuclear charge Z. Moreover, the Fisher-Shannon measure is shown to
quadratically depend on the principal quantum number n. Finally, sharp upper
bounds to the Fisher-Shannon measure and the shape complexity of a general
hydrogenic orbital are given in terms of the quantum numbers.Comment: 22 pages, 7 figures, accepted i
Bianchi Type I Universes with Causal Bulk Viscous Cosmological Fluid
We consider the dynamics of a causal bulk viscous cosmological fluid filled
constantly decelerating Bianchi type I space-time. The matter component of the
Universe is assumed to satisfy a linear barotropic equation of state and the
state equation of the small temperature Boltzmann gas. The resulting
cosmological models satisfy the condition of smallness of the viscous stress.
The time evolution of the relaxation time, temperature, bulk viscosity
coefficient and comoving entropy of the dissipative fluid is also obtained.Comment: 11 pages, 5 figures, accepted for publication in International
Journal of Modern Physics
Nuclear condensation and the equation of state of nuclear matter
The isothermal compression of a dilute nucleonic gas invoking cluster degrees
of freedom is studied in an equilibrium statistical model; this clusterized
system is found to be more stable than the pure nucleonic system. The equation
of state (EoS) of this matter shows features qualitatively very similar to the
one obtained from pure nucleonic gas. In the isothermal compression process,
there is a sudden enhancement of clusterization at a transition density
rendering features analogous to the gas-liquid phase transition in normal
dilute nucleonic matter. Different observables like the caloric curves, heat
capacity, isospin distillation, etc. are studied in both the models. Possible
changes in the observables due to recently indicated medium modifications in
the symmetry energy are also investigated.Comment: 18 pages and 11 figures. Phys. Rev. C (in press
How fundamental are fundamental constants?
I argue that the laws of physics should be independent of one's choice of
units or measuring apparatus. This is the case if they are framed in terms of
dimensionless numbers such as the fine structure constant, alpha. For example,
the Standard Model of particle physics has 19 such dimensionless parameters
whose values all observers can agree on, irrespective of what clock, rulers,
scales... they use to measure them. Dimensional constants, on the other hand,
such as h, c, G, e, k..., are merely human constructs whose number and values
differ from one choice of units to the next. In this sense only dimensionless
constants are "fundamental". Similarly, the possible time variation of
dimensionless fundamental "constants" of nature is operationally well-defined
and a legitimate subject of physical enquiry. By contrast, the time variation
of dimensional constants such as c or G on which a good many (in my opinion,
confusing) papers have been written, is a unit-dependent phenomenon on which
different observers might disagree depending on their apparatus. All these
confusions disappear if one asks only unit-independent questions.
We provide a selection of opposing opinions in the literature and respond
accordingly.Comment: Note added. 30 pages latex. 7 figures. arXiv admin note: text overlap
with arXiv:hep-th/0208093 (unpublished
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