18,155 research outputs found
Damping of bulk excitations over an elongated BEC - the role of radial modes
We report the measurement of Beliaev damping of bulk excitations in cigar
shaped Bose Einstein condensates of atomic vapor. By using post selection,
excitation line shapes of the total population are compared with those of the
undamped excitations. We find that the damping depends on the initial
excitation energy of the decaying quasi particle, as well as on the excitation
momentum. We model the condensate as an infinite cylinder and calculate the
damping rates of the different radial modes. The derived damping rates are in
good agreement with the experimentally measured ones. The damping rates
strongly depend on the destructive interference between pathways for damping,
due to the quantum many-body nature of both excitation and damping products.Comment: 5 pages, 4 figure
Dispersion Relations for Bernstein Waves in a Relativistic Pair Plasma
A fully relativistic treatment of Bernstein waves in an electron-positron
pair plasma has remained too formidable a task owing to the very complex nature
of the problem. In this article, we perform contour integration of the
dielectric response function and numerically compute the dispersion curves for
a uniform, magnetized, relativistic electron-positron pair plasma. The behavior
of the dispersion solution for several cases with different plasma temperatures
is highlighted. In particular, we find two wave modes that exist only for large
wavelengths and frequencies similar to the cyclotron frequency in a moderately
relativistic pair plasma. The results presented here have important
implications for the study of those objects where a hot magnetized
electron-positron plasma plays a fundamental role in generating the observed
radiation.Comment: 8 pages, 8 figures, Accepted for publication by Phys. Rev. E with
minor change
Nitrogen-vacancy singlet manifold ionization energy
The singlet states of the negatively-charged nitrogen-vacancy centers in
diamond play a key role in its optical spin control and readout. In this work,
the hitherto unknown ionization energy of the singlet is measured
experimentally and found to be between 1.91-2.25 eV. This is obtained by
analyzing photoluminescence measurements incorporating spin control and NV
charge state differentiation, along with simulations based on the
nitrogen-vacancy's master equation. This work establishes a protocol for a more
accurate estimate of this ionization energy, which can possibly lead to
improved read-out methods
Can remote STI/HIV testing and eClinical Care be compatible with robust public health surveillance?
In this paper we outline the current data capture systems for human immunodeficiency virus (HIV) and sexually transmitted infection (STI) surveillance used by Public Health England (PHE), and how these will be affected by the introduction of novel testing platforms and changing patient pathways. We outline the Chlamydia Online Clinical Care Pathway (COCCP), developed as part of the Electronic Self-Testing for Sexually Transmitted Infections (eSTI(2)) Consortium, which ensures that surveillance data continue to be routinely collected and transmitted to PHE. We conclude that both novel diagnostic testing platforms and established data capture systems must be adaptable to ensure continued robust public health surveillance
Convective Term and Transversely Driven Charge-Density Waves
We derive the convective terms in the damping which determine the structure
of the moving charge-density wave (CDW), and study the effect of a current
flowing transverse to conducting chains on the CDW dynamics along the chains.
In contrast to a recent prediction we find that the effect is orders of
magnitude smaller, and that contributions from transverse currents of electron-
and hole-like quasiparticles to the force exerted on the CDW along the chains
act in the opposite directions. We discuss recent experimental verification of
the effect and demonstrate experimentally that geometry effects might mimic the
transverse current effect.Comment: RevTeX, 9 pages, 1 figure, accepted for publications in PR
Unique Mass Texture for Quarks and Leptons
Texture specific quark mass matrices which are hermitian and hierarchical are
examined in detail . In the case of texture 6 zeros matrices, out of sixteen
possibilities examined by us, none is able to fit the low energy data (LED),
for example, , ,
, lies in the range (PDG). Similarly none of the 32 texture 5 zeros mass matrices considered
is able to reproduce LED. In particular, the latest data from LEP regarding
rules out all of them. In the texture 4
zeros case, we find that there is a unique texture structure for and
mass matrices which is able to fit the data.Comment: 12 pages, LaTeX,some changes in the references,minor changes in the
text,to appear in Phys Rev D(Rapid communications
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