12,848 research outputs found
Analyticity of the SRB measure for a class of simple Anosov flows
We consider perturbations of the Hamiltonian flow associated with the
geodesic flow on a surface of constant negative curvature. We prove that, under
a small perturbation, not necessarely of Hamiltonian character, the SRB measure
associated to the flow exists and is analytic in the strength of the
perturbation. An explicit example of "thermostatted" dissipative dynamics is
constructed.Comment: 23 pages, corrected typo
Ion yields and erosion rates for Si1−xGex(0x1) ultralow energy O2+ secondary ion mass spectrometry in the energy range of 0.25–1 keV
We report the SIMS parameters required for the quantitative analysis of Si1−xGex across the range of 0 ≤ x ≤ 1 when using low energy O2+ primary ions at normal incidence. These include the silicon and germanium secondary ion yield [i.e., the measured ion signal (ions/s)] and erosion rate [i.e., the speed at which the material sputters (nm/min)] as a function of x. We show that the ratio Rx of erosion rates, Si1−xGex/Si, at a given x is almost independent of beam energy, implying that the properties of the altered layer are dominated by the interaction of oxygen with silicon. Rx shows an exponential dependence on x. Unsurprisingly, the silicon and germanium secondary ion yields are found to depart somewhat from proportionality to (1−x) and x, respectively, although an approximate linear relationship could be used for quantification across around 30% of the range of x (i.e., a reference material containing Ge fraction x would give reasonably accurate quantification across the range of ±0.15x). Direct comparison of the useful (ion) yields [i.e., the ratio of ion yield to the total number of atoms sputtered for a particular species (ions/atom)] and the sputter yields [i.e., the total number of atoms sputtered per incident primary ion (atoms/ions)] reveals a moderate matrix effect where the former decrease monotonically with increasing x except at the lowest beam energy investigated (250 eV). Here, the useful yield of Ge is found to be invariant with x. At 250 eV, the germanium ion and sputter yields are proportional to x for all x
Statistical mechanics of damage phenomena
This paper applies the formalism of classical, Gibbs-Boltzmann statistical
mechanics to the phenomenon of non-thermal damage. As an example, a non-thermal
fiber-bundle model with the global uniform (meanfield) load sharing is
considered. Stochastic topological behavior in the system is described in terms
of an effective temperature parameter thermalizing the system. An equation of
state and a topological analog of the energy-balance equation are obtained. The
formalism of the free energy potential is developed, and the nature of the
first order phase transition and spinodal is demonstrated.Comment: Critical point appeared to be a spinodal poin
Laser cooling and control of excitations in superfluid helium
Superfluidity is an emergent quantum phenomenon which arises due to strong
interactions between elementary excitations in liquid helium. These excitations
have been probed with great success using techniques such as neutron and light
scattering. However measurements to-date have been limited, quite generally, to
average properties of bulk superfluid or the driven response far out of thermal
equilibrium. Here, we use cavity optomechanics to probe the thermodynamics of
superfluid excitations in real-time. Furthermore, strong light-matter
interactions allow both laser cooling and amplification of the thermal motion.
This provides a new tool to understand and control the microscopic behaviour of
superfluids, including phonon-phonon interactions, quantised vortices and
two-dimensional quantum phenomena such as the Berezinskii-Kosterlitz-Thouless
transition. The third sound modes studied here also offer a pathway towards
quantum optomechanics with thin superfluid films, including femtogram effective
masses, high mechanical quality factors, strong phonon-phonon and phonon-vortex
interactions, and self-assembly into complex geometries with sub-nanometre
feature size.Comment: 6 pages, 4 figures. Supplementary information attache
Collision of spinning black holes in the close limit
In this paper we consider the collision of spinning holes using first order
perturbation theory of black holes (Teukolsky formalism). With these results
(along with ones, we published in the past) one can predict the properties of
the gravitational waves radiated from the late stage inspiral of two spinning,
equal mass black holes. Also we note that the energy radiated by the head-on
collision of two spinning holes with spins (that are equal and opposite)
aligned along the common axis is more than the case in which the spins are
perpendicular to the axis of the collision.Comment: 6 pages, 3 figures, submitted to PR
Microphotonic Forces From Superfluid Flow
In cavity optomechanics, radiation pressure and photothermal forces are
widely utilized to cool and control micromechanical motion, with applications
ranging from precision sensing and quantum information to fundamental science.
Here, we realize an alternative approach to optical forcing based on superfluid
flow and evaporation in response to optical heating. We demonstrate optical
forcing of the motion of a cryogenic microtoroidal resonator at a level of 1.46
nN, roughly one order of magnitude larger than the radiation pressure force. We
use this force to feedback cool the motion of a microtoroid mechanical mode to
137 mK. The photoconvective forces demonstrated here provide a new tool for
high bandwidth control of mechanical motion in cryogenic conditions, and have
the potential to allow efficient transfer of electromagnetic energy to motional
kinetic energy.Comment: 5 pages, 6 figure
Finite temperature bosonization
Finite temperature properties of a non-Fermi liquid system is one of the most
challenging probelms in current understanding of strongly correlated electron
systems. The paradigmatic arena for studying non-Fermi liquids is in one
dimension, where the concept of a Luttinger liquid has arisen. The existence of
a critical point at zero temperature in one dimensional systems, and the fact
that experiments are all undertaken at finite temperature, implies a need for
these one dimensional systems to be examined at finite temperature.
Accordingly, we extended the well-known bosonization method of one dimensional
electron systems to finite temperatures. We have used this new bosonization
method to calculate finite temperature asymptotic correlation functions for
linear fermions, the Tomonaga-Luttinger model, and the Hubbard model.Comment: REVTex, 48 page
Collisions of boosted black holes: perturbation theory prediction of gravitational radiation
We consider general relativistic Cauchy data representing two nonspinning,
equal-mass black holes boosted toward each other. When the black holes are
close enough to each other and their momentum is sufficiently high, an
encompassing apparent horizon is present so the system can be viewed as a
single, perturbed black hole. We employ gauge-invariant perturbation theory,
and integrate the Zerilli equation to analyze these time-asymmetric data sets
and compute gravitational wave forms and emitted energies. When coupled with a
simple Newtonian analysis of the infall trajectory, we find striking agreement
between the perturbation calculation of emitted energies and the results of
fully general relativistic numerical simulations of time-symmetric initial
data.Comment: 5 pages (RevTex 3.0 with 3 uuencoded figures), CRSR-107
Thermodynamic formalism for field driven Lorentz gases
We analytically determine the dynamical properties of two dimensional field
driven Lorentz gases within the thermodynamic formalism. For dilute gases
subjected to an iso-kinetic thermostat, we calculate the topological pressure
as a function of a temperature-like parameter \ba up to second order in the
strength of the applied field. The Kolmogorov-Sinai entropy and the topological
entropy can be extracted from a dynamical entropy defined as a Legendre
transform of the topological pressure. Our calculations of the Kolmogorov-Sinai
entropy exactly agree with previous calculations based on a Lorentz-Boltzmann
equation approach. We give analytic results for the topological entropy and
calculate the dimension spectrum from the dynamical entropy function.Comment: 9 pages, 5 figure
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