2,318 research outputs found
Tundra Rodents in a Late Pleistocene Fauna from the Tofty Placer District, Central Alaska
Describes remains of the arctic ground squirrel, collared and brown lemmings, and the narrow-skulled vole collected 1956-1961 in or near the Sullivan mining pit. Topography, vegetation, and mining history are outlined, as are the stratigraphy and age of the unconsolidated deposits in which the fossils were found. The rodents, all typical tundra forms, are not now in the Tofty area which has been forested at least 6800 yr. Apparently, they represent the fauna of a colder climatic period during Wisconsin time
Toy Model for Pion Production in Nucleon-Nucleon Collisions
We develop a toy model of pion production in nucleon-nucleon collisions that
reproduces some of the features of the chiral Lagrangian calculations. We
calculate the production amplitude and examine some common approximations.Comment: 9 pages, 3 figure
Neurocognitive Development of Motivated Behavior: Dynamic Changes across Childhood and Adolescence
A wavelet analysis of the Rosenblatt process: chaos expansion and estimation of the self-similarity parameter
By using chaos expansion into multiple stochastic integrals, we make a
wavelet analysis of two self-similar stochastic processes: the fractional
Brownian motion and the Rosenblatt process. We study the asymptotic behavior of
the statistic based on the wavelet coefficients of these processes. Basically,
when applied to a non-Gaussian process (such as the Rosenblatt process) this
statistic satisfies a non-central limit theorem even when we increase the
number of vanishing moments of the wavelet function. We apply our limit
theorems to construct estimators for the self-similarity index and we
illustrate our results by simulations
Outskirts of Distant Galaxies In Absorption
QSO absorption spectroscopy provides a sensitive probe of both the neutral
medium and diffuse ionized gas in the distant Universe. It extends 21cm maps of
gaseous structures around low-redshift galaxies both to lower gas column
densities and to higher redshifts. Combining galaxy surveys with
absorption-line observations of gas around galaxies enables comprehensive
studies of baryon cycles in galaxy outskirts over cosmic time. This Chapter
presents a review of the empirical understanding of the cosmic neutral gas
reservoir from studies of damped Lya absorbers (DLAs). It describes the
constraints on the star formation relation and chemical enrichment history in
the outskirts of distant galaxies from DLA studies. A brief discussion of
available constraints on the ionized circumgalactic gas from studies of lower
column density Lya absorbers and associated ionic absorption transitions is
presented at the end.Comment: 45 pages, 7 figures, invited review, Book chapter in "Outskirts of
Galaxies", Eds. J. H. Knapen, J. C. Lee and A. Gil de Paz, Astrophysics and
Space Science Library, Springer, in pres
Glueball production in radiative J/psi, Upsilon decays
Using a bound-state model of weakly bound gluons for glueballs made of two
gluons and a natural generalization of the perturbative QCD formalism for
exclusive hadronic processes, we present results for glueball production in
radiative J/psi, Upsilon decays into several possible glueball states,
including L \not= 0 ones. We perform a detailed phenomenological analysis,
presenting results for the more favored experimental candidates and for decay
angular distributions.Comment: RevTeX4, 26 pages, 11 eps figure
Implications of quantum automata for contextuality
We construct zero-error quantum finite automata (QFAs) for promise problems
which cannot be solved by bounded-error probabilistic finite automata (PFAs).
Here is a summary of our results:
- There is a promise problem solvable by an exact two-way QFA in exponential
expected time, but not by any bounded-error sublogarithmic space probabilistic
Turing machine (PTM).
- There is a promise problem solvable by an exact two-way QFA in quadratic
expected time, but not by any bounded-error -space PTMs in
polynomial expected time. The same problem can be solvable by a one-way Las
Vegas (or exact two-way) QFA with quantum head in linear (expected) time.
- There is a promise problem solvable by a Las Vegas realtime QFA, but not by
any bounded-error realtime PFA. The same problem can be solvable by an exact
two-way QFA in linear expected time but not by any exact two-way PFA.
- There is a family of promise problems such that each promise problem can be
solvable by a two-state exact realtime QFAs, but, there is no such bound on the
number of states of realtime bounded-error PFAs solving the members this
family.
Our results imply that there exist zero-error quantum computational devices
with a \emph{single qubit} of memory that cannot be simulated by any finite
memory classical computational model. This provides a computational perspective
on results regarding ontological theories of quantum mechanics \cite{Hardy04},
\cite{Montina08}. As a consequence we find that classical automata based
simulation models \cite{Kleinmann11}, \cite{Blasiak13} are not sufficiently
powerful to simulate quantum contextuality. We conclude by highlighting the
interplay between results from automata models and their application to
developing a general framework for quantum contextuality.Comment: 22 page
Threshold temperature for pairwise and many-particle thermal entanglement in the isotropic Heisenberg model
We study the threshold temperature for pairwise thermal entanglement in the
spin-1/2 isotropic Heisenberg model up to 11 spins and find that the threshold
temperature for odd and even number of qubits approaches the thermal dynamical
limit from below and above, respectively. The threshold temperature in the
thermodynamical limit is estimated. We investigate the many-particle
entanglement in both ground states and thermal states of the system, and find
that the thermal state in the four-qubit model is four-particle entangled
before a threshold temperature.Comment: 4 pages with 1 fig. More discussions on many-particle ground-state
and thermal entanglement in the multiqubit Heisenberg model from 2 to 11
qubits are adde
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