1,174 research outputs found
Entanglement entropy of -vacua in de Sitter space
We consider the entanglement entropy of a free massive scalar field in the
one parameter family of -vacua in de Sitter space by using a method
developed by Maldacena and Pimentel. An -vacuum can be thought of as a
state filled with particles from the point of view of the Bunch-Davies vacuum.
Of all the -vacua we find that the entanglement entropy takes the
minimal value in the Bunch-Davies solution. We also calculate the asymptotic
value of the R\'enyi entropy and find that it increases as increases.
We argue these feature stem from pair condensation within the non-trivial
-vacua where the pairs have an intrinsic quantum correlation.Comment: 23 pages, 6 figures. Two figures and references adde
Braneworld Flux Inflation
We propose a geometrical model of brane inflation where inflation is driven
by the flux generated by opposing brane charges and terminated by the collision
of the branes, with charge annihilation. We assume the collision process is
completely inelastic and the kinetic energy is transformed into the thermal
energy after collision. Thereafter the two branes coalesce together and behave
as a single brane universe with zero effective cosmological constant. In the
Einstein frame, the 4-dimensional effective theory changes abruptly at the
collision point. Therefore, our inflationary model is necessarily 5-dimensional
in nature. As the collision process has no singularity in 5-dimensional
gravity, we can follow the evolution of fluctuations during the whole history
of the universe. It turns out that the radion field fluctuations have a steeply
tilted, red spectrum, while the primordial gravitational waves have a flat
spectrum. Instead, primordial density perturbations could be generated by a
curvaton mechanism.Comment: 11 pages, 6 figures, references adde
Properties of the superconducting state in a two-band model
Eliashberg theory is used to investigate the range of thermodynamic
properties possible within a two-band model for s-wave superconductivity and to
identify signatures of its two-band nature. We emphasize dimensionless BCS
ratios (those for the energy gaps, the specific heat jump and the negative of
its slope near Tc, the thermodynamic critical field Hc(0), and the normalized
slopes of the critical field and the penetration depth near Tc), which are no
longer universal even in weak coupling. We also give results for
temperature-dependent quantities, such as the penetration depth and the energy
gap. Results are presented both for microscopic parameters appropriate to MgB2
and for variations away from these. Strong coupling corrections are identified
and found to be significant. Analytic formulas are provided which show the role
played by the anisotropy in coupling in some special limits. Particular
emphasis is placed on small interband coupling and on the opposite limit of no
diagonal coupling. The effect of impurity scattering is considered,
particularly for the interband case.Comment: 20 pages, 14 figures, final version accepted in PR
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MyPHRMachines: Lifelong Personal Health Records in the Cloud
Personal Health Records (PHRs) should remain the lifelong property of patients and should be showable conveniently and securely to selected caregivers. Regarding interoperability, current solutions for PHRs focus on standard data exchange formats and transformations to move data across health information systems. In this paper we propose MyPHRMachines, a patient-centric system that takes a radically new architectural solution to health record interoperability. We propose to deploy besides the medical data also the related software to the PHR system. After uploading their medical data to MyPHRMachines, patients can access them again from remote virtual machines that contain the right software to visualize and analyze them without any conversion. Patients can share their remote virtual machine session with a selected health provider, who will need only a Web browser to access the pre-loaded fragments of the lifelong PHR. We illustrate how our prototype already supports the use case of a real-world patient and discuss the research agenda required to translate this prototype into a viable solution for the international healthcare industry
Evaluation of commercial adjuncts for use in cheese ripening: 5. Effect of added freeze-shocked adjunct lactobacilli on proteolysis and sensory quality of reduced fat Cheddar cheese
Higher Curvature Corrections to Primordial Fluctuations in Slow-roll Inflation
We study higher curvature corrections to the scalar spectral index, the
tensor spectral index, the tensor-to-scalar ratio, and the polarization of
gravitational waves. We find that the higher curvature corrections can not be
negligible in the dynamics of the scalar field, although they are energetically
negligible. Indeed, it turns out that the tensor-to-scalar ratio could be
enhanced and the tensor spectral index could be blue due to the Gauss-Bonnet
term. We estimate the degree of circular polarization of gravitational waves
generated during the slow-roll inflation. We argue that the circular
polarization can be observable with the help both of the Gauss-Bonnet and
parity violating terms. We also present several examples to reveal
observational implications of higher curvature corrections for chaotic
inflationary models.Comment: 12 pages, 4 figure
Position controlled self-catalyzed growth of GaAs nanowires by molecular beam epitaxy
GaAs nanowires are grown by molecular beam epitaxy using a self-catalyzed,
Ga-assisted growth technique. Position control is achieved by nano-patterning a
SiO2 layer with arrays of holes with a hole diameter of 85 nm and a hole pitch
varying between 200 nm and 2 \mum. Gallium droplets form preferentially at the
etched holes acting as catalyst for the nanowire growth. The nanowires have
hexagonal cross-sections with {110} side facets and crystallize predominantly
in zincblende. The interdistance dependence of the nanowire growth rate
indicates a change of the III/V ratio towards As-rich conditions for large hole
distances inhibiting NW growth.Comment: 9 pages, 4 figure
Magnetic and Metal-Insulator Transitions in beta-Na0.5CoO2 and gamma-K0.5CoO2 -NMR and Neutron Diffraction Studies-
Co-oxides beta-Na0.5CoO2 and gamma-K0.5CoO2 have been prepared by the Na
de-intercalation from alpha-NaCoO2 and by the floating-zone method,
respectively. It has been found that successive phase transitions take place at
temperatures Tc1 and Tc2 in both systems. The appearance of the internal
magnetic field at Tc1 with decreasing temperature T indicates that the
antiferromagnetic order exists at T < Tc1, as in gamma-Na0.5CoO2. For
beta-Na0.5CoO2, the transition temperatures and the NMR parameters determined
from the data taken for magnetically ordered state are similar to those of
gamma-Na0.5CoO2, indicating that the difference of the stacking ways of the
CoO2 layers between these systems do not significantly affect their physical
properties. For gamma-K0.5CoO2, the quantitative difference of the physical
quantities are found from those of beta- and gamma-Na0.5CoO2. The difference
between the values of Tci (i = 1 and 2) of these systems might be explained by
considering the distance between CoO2 layers.Comment: 8 pages, 14 figures, 1 Tabl
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