2,525 research outputs found
Getting Super-Excited with Modified Dispersion Relations
We demonstrate that in some regions of parameter space, modified dispersion
relations can lead to highly populated excited states, which we dub as
"super-excited" states. In order to prepare such super-excited states, we
invoke dispersion relations that have negative slope in an interim sub-horizon
phase at high momenta. This behaviour of quantum fluctuations can lead to large
corrections relative to the Bunch-Davies power spectrum, which mimics highly
excited initial conditions. We identify the Bogolyubov coefficients that can
yield these power spectra. In the course of this computation, we also point out
the shortcomings of the gluing method for evaluating the power spectrum and the
Bogolyubov coefficients. As we discuss, there are other regions of parameter
space, where the power spectrum does not get modified. Therefore, modified
dispersion relations can also lead to so-called "calm excited states" as well.
We conclude by commenting on the possibility of obtaining these modified
dispersion relations within the Effective Field Theory of Inflation.Comment: 1+19 pages, 4 figure
Trajectory of test particle around a slowly rotating relativistic star emitting isotropic radiation
We explored the motion of test particles near slowly rotating relativistic
star having a uniform luminosity. In order to derive the test particle's
equations of motion, we made use of the radiation stress-energy tensor first
constructed by Miller and Lamb \cite{ML96}. From the particle's trajectory
obtained through the numerical integration of the equations of motion, it is
found that for sufficiently high luminosity, "suspension orbit" exists, where
the test particle hovers around at uniform angular velocity in the same
direction as the star's spin. Interestingly, it turned out that the radial
position of the "suspension orbit" was determined by the luminosity and the
angular momentum of the star alone and was independent of the initial positions
and the specific angular momentum of the particle. Also found is that there
exist not only the radiation drag but also "radiation counter-drag" which
depends on the stellar radius and the angular momentum and it is this radiation
counter-drag that makes the test particle in the "suspension orbit" to hover
around at uniform angular velocity which is greater than that induced by the
Lense-Thirring effect (i.e., general relativistic dragging of inertial frame).Comment: 23 pages, 7 figures, to appear in Phys. Rev. D
Extended Effective Field Theory of Inflation
We present a general framework where the effective field theory of single
field inflation is extended by the inclusion of operators with mass dimension 3
and 4 in the unitary gauge. These higher dimensional operators introduce
quartic and sextic corrections to the dispersion relation. We study the regime
of validity of this extended effective field theory of inflation and the effect
of these higher dimensional operators on CMB observables associated with scalar
perturbations, such as the speed of sound, the amplitude of the power spectrum
and the tensor-to-scalar ratio. Tensor perturbations remain instead, unaltered.Comment: new version matches the published version, includes adding few
citations and correcting few typo
Dielectric relaxation of the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate: microwave and far-IR properties
Dielectric relaxation of the ionic liquid, 1-ethyl-3-methylimidazolium ethyl sulfate (EMI+ETSâ), is studied using molecular dynamics (MD) simulations. The collective dynamics of polarization arising from cations and anions are examined. Characteristics of the rovibrational and translational components of polarization dynamics are analyzed to understand their respective roles in the microwave and terahertz regions of dielectric relaxation. The MD results are compared with the experimental low-frequency spectrum of EMI+ETSâ, obtained via ultrafast optical Kerr effect (OKE) measurements
A molecular dynamics computer simulation study of room-temperature ionic liquids. I. Equilibrium solvation structure and free energetics
Solvation in 1-ethyl-3-methylmidazolium chloride and in
1-ethyl-3-methylimidazolium hexafluorophosphate near equilibrium is
investigated via molecular dynamics computer simulations with diatomic and
benzenelike molecules employed as probe solutes. It is found that
electrostriction plays an important role in both solvation structure and free
energetics. The angular and radial distributions of cations and anions become
more structured and their densities near the solute become enhanced as the
solute charge separation grows. Due to the enhancement in structural rigidity
induced by electrostriction, the force constant associated with solvent
configuration fluctuations relevant to charge shift and transfer processes is
also found to increase. The effective polarity and reorganization free energies
of these ionic liquids are analyzed and compared with those of highly polar
acetonitrile. Their screening behavior of electric charges is also
investigated.Comment: 12 page
Blackbody radiation in \kappa-Minkowski spacetime
We have computed the black body radiation spectra in Minkowski
space-time, using the quantum mechanical picture of massless scalar particles
as well as effective quantum field theory picture. The black body radiation
depends on how the field theory (and thus how the Poincar\'e algebra)
handles the ordering effect of the noncommutative space-time. In addition,
there exists a natural momentum cut-off of the order , beyond which a
new real mode takes its shape from a complex mode and the old real mode flows
out to be a new complex mode. However, the new high momentum real mode should
not be physical since its contributions to the black-body radiation spoils the
commutative limit.Comment: 22pages, No figure, some corrections, to appear in Phys. Rev.
Removal of Confined Ionic Liquid from a Metal Organic Framework by Extraction with Molecular Solvents
This work was supported in part by NSF Grant No. CHE-1223988 and by EPSRC Grant No. EP/K00090X/1.Peer reviewedPostprin
A Case of Birt-Hogg-Dubé Syndrome
Birt-Hogg-Dubé syndrome (BHDS) is an autosomal dominant genodermatosis characterized by cutaneous hair follicle tumors (fibrofolliculoma or trichodiscoma), pulmonary cysts, and increased risk of renal neoplasia. The genetic alteration for BHDS has been mapped to chromosome 17p12q11, and the gene in this region has been cloned and believed to be responsible for the BHDS. Mutations in the BHD gene (also known as FLCN) have been described in the patients with BHDS. We present a case of a 30-yr-old Korean woman with multiple mildly pruritic papules on her face and neck area. The patient had several firm, flesh-colored, dome-shaped, papular lesions measuring between 2 to 5 mm. Except for a history of pneumothorax her medical records were not remarkable. Mutation analysis of the BHD gene was performed, and a novel deletion mutation (p.F519LfsX17 [c.1557delT]) causing truncation of the gene product, folliculin, was found in the exon 14. The actual incidence of BHDS is unknown, but it is most likely underdiagnosed. So it is imperative that doctors recognize the skin lesions of BHDS and institute proper screening to detect other manifestations of the disease. Here, we report a case of BHDS with a novel mutation, which is the first report in Korea
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