11,074 research outputs found
Adaptive Control: Actual Status and Trends
Important progress in research and application of Adaptive Control Systems has been achieved in the last ten years. The techniques which are currently used in applications will be reviewed. Theoretical aspects currently under investigation and which are related to the application of adaptive control techniques in various fields will be briefly discussed. Applications in various areas will be briefly reviewed. The use of adaptive techniques for vibrations monitoring and active vibration control will be emphasized
A heuristic approach to the weakly interacting Bose gas
Some thermodynamic properties of weakly interacting Bose systems are derived
from dimensional and heuristic arguments and thermodynamic relations, without
resorting to statistical mechanics
Magnetoelasticity theory of incompressible quantum Hall liquids
A simple and physically transparent magnetoelasticity theory is proposed to
describe linear dynamics of incompressible fractional quantum Hall states. The
theory manifestly satisfies the Kohn theorem and the -sum rule, and predicts
a gaped intra-Landau level collective mode with a roton minimum. In the limit
of vanishing bare mass the correct form of the static structure factor,
, is recovered. We establish a connection of the present approach
to the fermionic Chern-Simons theory, and discuss further extensions and
applications. We also make an interesting analogy of the present theory to the
theory of visco-elastic fluids.Comment: RevTeX 4, 6 pages; expanded version to appear in PRB; more technical
details, and discussions of the physics adde
Microwave Response and Spin Waves in Superconducting Ferromagnets
Excitation of spin waves is considered in a superconducting ferromagnetic
slab with the equilibrium magnetization both perpendicular and parallel to the
surface. The surface impedance is calculated and its behavior near propagation
thresholds is analyzed. Influence of non-zero magnetic induction at the surface
is considered in various cases. The results provide a basis for investigation
of materials with coexisting superconductivity and magnetism by microwave
response measurements.Comment: 10 pages, 7 figure
On an exact hydrodynamic solution for the elliptic flow
Looking for the underlying hydrodynamic mechanisms determining the elliptic
flow we show that for an expanding relativistic perfect fluid the transverse
flow may derive from a solvable hydrodynamic potential, if the entropy is
transversally conserved and the corresponding expansion "quasi-stationary",
that is mainly governed by the temperature cooling. Exact solutions for the
velocity flow coefficients and the temperature dependence of the spatial
and momentum anisotropy are obtained and shown to be in agreement with the
elliptic flow features of heavy-ion collisions.Comment: 10 pages, 4 figure
Polarons in suspended carbon nanotubes
We prove theoretically the possibility of electric-field controlled polaron
formation involving flexural (bending) modes in suspended carbon nanotubes.
Upon increasing the field, the ground state of the system with a single extra
electron undergoes a first order phase transition between an extended state and
a localized polaron state. For a common experimental setup, the threshold
electric field is only of order V/m
Surprises in nonperturbative dynamics in sigma-model at finite density
The linear sigma-model occupies a unique place in
elementary particle physics and quantum field theory. It has been recently
realized that when a chemical potential for hypercharge is added, it becomes a
toy model for the description of the dynamics of the kaon condensate in high
density QCD. We review recent results in nonperturbative dynamics obtained in
the ungauged and gauged versions of this model.Comment: Brief review. 16 pages, 5 figure
Giant enhancement of room temperature magnetoresistance in La_{0.67}Sr_{0.33}MnO_{3}/Nd_{0.67}Sr_{0.33}MnO_{3} multilayers
The metal-insulator transition temperature in CMR manganites has been altered
and brought close to the room temperature by preparing
LaSrMnO (LSMO)/ NdSrMnO (NSMO)
multilayers with ultra thin individual layers of LSMO and NSMO. The LSMO/NSMO
multilayers with ultra thin individual layers of thickness of about
exhibits 150% magnetoresistance at 270 K whereas LSMO/NSMO multilayers with
moderate individual layer thickness of about each exhibits a mere 15%
magnetoresistance at the same temperature. We have shown that the reduction in
thickness of the individual layers leads to increased spin fluctuation which
results in the enhancement of magnetoresistance.Comment: Replaced with revised version and new figure, 9 pages, 4 figure
Time Modulation of K-electron Capture Decay of Hydrogen-Like Ions with Multiphoton Resonance Transitions
The multiphoton resonance transitions between ground hyperfine states are
used for the time modulation of the electron capture decay of hydrogen like
ions with the Gamow-Teller transition . The proposed mechanism
offers a time oscillating decay with the frequency up to 0.1 Hz. The experiment
to observe the modulation is proposed for ions stored in a Penning trap. An
attempt to understand the GSI anomaly with multiple photon transitions is made.Comment: 5 pages, REVTeX. Added text and a reference
Relativistic Theory of Hydrodynamic Fluctuations with Applications to Heavy Ion Collisions
We develop the relativistic theory of hydrodynamic fluctuations for
application to high energy heavy ion collisions. In particular, we investigate
their effect on the expanding boost-invariant (Bjorken) solution of the
hydrodynamic equations. We discover that correlations over a long rapidity
range are induced by the propagation of the sound modes. Due to the expansion,
the dispersion law for these modes is non-linear and attenuated even in the
limit of zero viscosity. As a result, there is a non-dissipative wake behind
the sound front which is generated by any instantaneous point-like fluctuation.
We evaluate the two-particle correlators using the initial conditions and
hydrodynamic parameters relevant for heavy-ion collisions at RHIC and LHC. In
principle these correlators can be used to obtain information about the
viscosities because the magnitudes of the fluctuations are directly
proportional to them.Comment: 39 pages, 6 figures; references adde
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