54 research outputs found
On the growth of perturbations in interacting dark energy and dark matter fluids
The covariant generalizations of the background dark sector coupling
suggested in G. Mangano, G. Miele and V. Pettorino, Mod. Phys. Lett. A 18, 831
(2003) are considered. The evolution of perturbations is studied with detailed
attention to interaction rate that is proportional to the product of dark
matter and dark energy densities. It is shown that some classes of models with
coupling of this type do not suffer from early time instabilities in strong
coupling regime.Comment: 11 pages, 2 figures. v3: minor changes, typos fixe
Superfluid Bosons and Flux Liquids: Disorder, Thermal Fluctuations, and Finite-Size Effects
The influence of different types of disorder (both uncorrelated and
correlated) on the superfluid properties of a weakly interacting or dilute Bose
gas, as well as on the corresponding quantities for flux line liquids in
high-temperature superconductors at low magnetic fields are reviewed,
investigated and compared. We exploit the formal analogy between superfluid
bosons and the statistical mechanics of directed lines, and explore the
influence of the different "imaginary time" boundary conditions appropriate for
a flux line liquid. For superfluids, we discuss the density and momentum
correlations, the condensate fraction, and the normal-fluid density as function
of temperature for two- and three-dimensional systems subject to a space- and
time-dependent random potential as well as conventional point-, line-, and
plane-like defects. In the case of vortex liquids subject to point disorder,
twin boundaries, screw dislocations, and various configurations of columnar
damage tracks, we calculate the corresponding quantities, namely density and
tilt correlations, the ``boson'' order parameter, and the tilt modulus. The
finite-size corrections due to periodic vs. open "imaginary time" boundary
conditions differ in interesting and important ways. Experimental implications
for vortex lines are described briefly.Comment: 78 pages, RevTex, 4 figures included (sorry, there are no ps-files
for the remaining 2 figures; if needed, please send mail to
[email protected]); brief erratum appended (2 pages
Quantum Rings in Electromagnetic Fields
This is the author accepted manuscript. The final version is available from Springer via the DOI in this recordThis chapter is devoted to optical properties of so-called Aharonov-Bohm
quantum rings (quantum rings pierced by a magnetic flux resulting in AharonovBohm
oscillations of their electronic spectra) in external electromagnetic fields.
It studies two problems. The first problem deals with a single-electron AharonovBohm
quantum ring pierced by a magnetic flux and subjected to an in-plane (lateral)
electric field. We predict magneto-oscillations of the ring electric dipole moment.
These oscillations are accompanied by periodic changes in the selection rules for
inter-level optical transitions in the ring allowing control of polarization properties
of the associated terahertz radiation. The second problem treats a single-mode microcavity
with an embedded Aharonov-Bohm quantum ring which is pierced by a
magnetic flux and subjected to a lateral electric field. We show that external electric
and magnetic fields provide additional means of control of the emission spectrum
of the system. In particular, when the magnetic flux through the quantum ring is
equal to a half-integer number of the magnetic flux quanta, a small change in the
lateral electric field allows for tuning of the energy levels of the quantum ring into
resonance with the microcavity mode, thus providing an efficient way to control
the quantum ring-microcavity coupling strength. Emission spectra of the system are
discussed for several combinations of the applied magnetic and electric fields
Histomorphological changes in gill epithelium of kaluga Acipenser dauricus and Amur sturgeon Acipenser schrenckii (Acipenseridae) from the Amur estuary
Simulation of hydraulic fracture propagation near a natural fracture using virtual multidimensional internal bonds
Characterisation of a novel electron beam lithography resist, SML and its comparison to PMMA and ZEP resists
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