9,679 research outputs found
The Three-Nucleon System Near the N-d Threshold
The three-nucleon system is studied at energies a few hundred keV above the
N-d threshold. Measurements of the tensor analyzing powers and
for p-d elastic scattering at keV are presented
together with the corresponding theoretical predictions. The calculations are
extended to very low energies since they are useful for extracting the p-d
scattering lengths from the experimental data. The interaction considered here
is the Argonne V18 potential plus the Urbana three-nucleon potential. The
calculation of the asymptotic D- to S-state ratio for H and He, for
which recent experimental results are available, is also presented.Comment: Latex, 11 pages, 2 figures, to be published in Phy.Lett.
New first integral for twisting type-N vacuum gravitational fields with two non-commuting Killing vectors
A new first integral for the equations corresponding to twisting type-N
vacuum gravitational fields with two non-commuting Killing vectors is
introduced. A new reduction of the problem to a complex second-order ordinary
differential equation is given. Alternatively, the mentioned first integral can
be used in order to provide a first integral of the second-order complex
equation introduced in a previous treatment of the problem.Comment: 7 pages, LaTeX, uses ioplppt.sty and iopl12.sty; to be published in
Class. Quantum Gra
Strong coupling of a mechanical oscillator and a single atom
We propose and analyze a setup to achieve strong coupling between a single
trapped atom and a mechanical oscillator. The interaction between the motion of
the atom and the mechanical oscillator is mediated by a quantized light field
in a laser driven high-finesse cavity. In particular, we show that high
fidelity transfer of quantum states between the atom and the mechanical
oscillator is in reach for existing or near future experimental parameters. Our
setup provides the basic toolbox for coherent manipulation, preparation and
measurement of micro- and nanomechanical oscillators via the tools of atomic
physics.Comment: 4 pages, 2 figures, minro changes, accepted by PR
Evidence for Three Nucleon Force Effects in p-d Elastic Scattering
A new measurement of the p-d differential cross section at Ep= 1 MeV has been
performed. These new data and older data sets at energies below the deuteron
breakup are compared to calculations using the two-nucleon Argonne v18 and the
three-nucleon Urbana IX potentials. A quantitative estimate of the capability
of these interactions to describe the data is given in terms of a chi^2
analysis. The chi^2 per datum drastically improves when the three-nucleon
interaction is included in the Hamiltonian.Comment: 13 pages, 5 figures, to be published in Phys. Rev.
On the Wake Structure in Streaming Complex Plasmas
The theoretical description of complex (dusty) plasmas requires multiscale
concepts that adequately incorporate the correlated interplay of streaming
electrons and ions, neutrals, and dust grains. Knowing the effective dust-dust
interaction, the multiscale problem can be effectively reduced to a
one-component plasma model of the dust subsystem. The goal of the present
publication is a systematic evaluation of the electrostatic potential
distribution around a dust grain in the presence of a streaming plasma
environment by means of two complementary approaches: (i) a high precision
computation of the dynamically screened Coulomb potential from the dynamic
dielectric function, and (ii) full 3D particle-in-cell simulations, which
self-consistently include dynamical grain charging and non-linear effects. The
applicability of these two approaches is addressed
Precision Measurements of d(d,p)t and d(d,n)^3He Total Cross Sections at Big-Bang Nucleosynthesis Energies
Recent Wilkinson Microwave Anisotropy Probe (WMAP) measurements have
determined the baryon density of the Universe with a precision of
about 4%. With tightly constrained, comparisons of Big Bang
Nucleosynthesis (BBN) abundance predictions to primordial abundance
observations can be made and used to test BBN models and/or to further
constrain abundances of isotopes with weak observational limits. To push the
limits and improve constraints on BBN models, uncertainties in key nuclear
reaction rates must be minimized. To this end, we made new precise measurements
of the d(d,p)t and d(d,n)^3He total cross sections at lab energies from 110 keV
to 650 keV.
A complete fit was performed in energy and angle to both angular distribution
and normalization data for both reactions simultaneously. By including
parameters for experimental variables in the fit, error correlations between
detectors, reactions, and reaction energies were accurately tabulated by
computational methods. With uncertainties around 2% +/- 1% scale error, these
new measurements significantly improve on the existing data set. At relevant
temperatures, using the data of the present work, both reaction rates are found
to be about 7% higher than those in the widely used Nuclear Astrophysics
Compilation of Reaction Rates (NACRE). These data will thus lead not only to
reduced uncertainties, but also to modifications in the BBN abundance
predictions.Comment: 15 pages, 11 figures, minor editorial change
An electron jet pump: The Venturi effect of a Fermi liquid
A three-terminal device based on a two-dimensional electron system is
investigated in the regime of non-equilibrium transport. Excited electrons
scatter with the cold Fermi sea and transfer energy and momentum to other
electrons. A geometry analogous to a water jet pump is used to create a jet
pump for electrons. Because of its phenomenological similarity we name the
observed behavior "electronic Venturi effect".Comment: Journal of Applied Physics Special Topic: Plenary and Invited Papers
from the 30th International Conference on the Physics of Semiconductors,
Seoul, Korea, 2010; http://link.aip.org/link/?JAP/109/10241
Finite quantum dissipation: the challenge of obtaining specific heat
We consider a free particle coupled with finite strength to a bath and
investigate the evaluation of its specific heat. A harmonic oscillator bath of
Drude type with cutoff frequency omega_D is employed to model an ohmic friction
force with dissipation strength gamma. Two scenarios for obtaining specific
heat are presented. The first one uses the measurement of the kinetic energy of
the free particle while the second one is based on the reduced partition
function. Both descriptions yield results which are consistent with the Third
Law of thermodynamics. Nevertheless, the two methods produce different results
that disagree even in their leading quantum corrections at high temperatures.
We also consider the regime where the cutoff frequency is smaller than the
friction strength, i.e. omega_D<gamma. There, we encounter puzzling results at
low temperatures where the specific heat based on the thermodynamic
prescription becomes negative. This anomaly is rooted in an ill-defined density
of states of the damped free particle which assumes unphysical negative values
when gamma/omega_D>1.Comment: 16 pages, 4 figure
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