1,488 research outputs found
Wave Solutions of Evolution Equations and Hamiltonian Flows on Nonlinear Subvarieties of Generalized Jacobians
The algebraic-geometric approach is extended to study solutions of
N-component systems associated with the energy dependent Schrodinger operators
having potentials with poles in the spectral parameter, in connection with
Hamiltonian flows on nonlinear subvariaties of Jacobi varieties. The systems
under study include the shallow water equation and Dym type equation. The
classes of solutions are described in terms of theta-functions and their
singular limits by using new parameterizations. A qualitative description of
real valued solutions is provided
On Soliton-type Solutions of Equations Associated with N-component Systems
The algebraic geometric approach to -component systems of nonlinear
integrable PDE's is used to obtain and analyze explicit solutions of the
coupled KdV and Dym equations. Detailed analysis of soliton fission, kink to
anti-kink transitions and multi-peaked soliton solutions is carried out.
Transformations are used to connect these solutions to several other equations
that model physical phenomena in fluid dynamics and nonlinear optics.Comment: 43 pages, 16 figure
Lifetimes and Sizes from Two-Particle Correlation Functions
We discuss the Yano-Koonin-Podgoretskii (YKP) parametrization of the
two-particle correlation function for azimuthally symmetric expanding sources.
We derive model-independent expressions for the YKP fit parameters and discuss
their physical interpretation. We use them to evaluate the YKP fit parameters
and their momentum dependence for a simple model for the emission function and
propose new strategies for extracting the source lifetime. Longitudinal
expansion of the source can be seen directly in the rapidity dependence of the
Yano-Koonin velocity.Comment: 15 pages REVTEX, 2 figures included, submitted to Phys. Lett. B,
Expanded discussion of disadvantages of standard HBT fit and of Fig.
Universal Pion Freeze-out Phase-Space Density
Results on the pion freeze-out phase-space density in sulphur-nucleus, Pb-Pb
and pion-proton collisions at CERN-SPS are presented. All heavy-ion reactions
are consistent with the thermal Bose-Einstein distrtibution f=1/(exp(E/T)-1) at
T~120 MeV, modified for expansion. Pion-proton data are also consistent with f,
but at T~180 MeV.Comment: 1 page, 1 figure; 98' report for GSI-Darmstad
Qubits entanglement dynamics modified by an effective atomic environment
We study entanglement dynamics of a couple of two-level atoms resonantly
interacting with a cavity mode and embedded in a dispersive atomic environment.
We show that in the absence of the environment the entanglement reaches its
maximum value when only one exitation is involved. Then, we find that the
atomic environment modifies that entanglement dynamics and induces a typical
collapse-revival structure even for an initial one photon Fock state of the
field.Comment: eight pages, two figure include
Transition from a phase-segregated state to single-phase incommensurate sodium ordering in Na_xCoO_2 with x \approx 0.53
Synchrotron X-ray diffraction investigations of two single crystals of
Na_xCoO_2 from different batches with composition x = 0.525-0.530 reveal
homogeneous incommensurate sodium ordering with propagation vector (0.53 0.53
0) at room-temperature. The incommensurate (qq0) superstructure exists between
220 K and 430 K. The value of q varies between q = 0.514 and 0.529, showing a
broad plateau at the latter value between 260 K and 360 K. On cooling, unusual
reversible phase segregation into two volume fractions is observed. Below 220
K, one volume fraction shows the well-known commensurate orthorhombic x = 0.50
superstructure, while a second volume fraction with x = 0.55 exhibits another
commensurate superstructure, presumably with a 6a x 6a x c hexagonal supercell.
We argue that the commensurate-to-incommensurate transition is an intrinsic
feature of samples with Na concentrations x = 0.5 + d with d ~ 0.03.Comment: Corrected/improved versio
Decoherence assisting a measurement-driven quantum evolution process
We study the problem of driving an unknown initial mixed quantum state onto a
known pure state without using unitary transformations. This can be achieved,
in an efficient manner, with the help of sequential measurements on at least
two unbiased bases. However here we found that, when the system is affected by
a decoherence mechanism, only one observable is required in order to achieve
the same goal. In this way the decoherence can assist the process. We show
that, depending on the sort of decoherence, the process can converge faster or
slower than the method implemented by means of two complementary observables.Comment: Four pages, three figures included ([email protected]
Enhancement of singly and multiply strangeness in p-Pb and Pb-Pb collisions at 158A GeV/c
The idea that the reduction of the strange quark suppression in string
fragmentation leads to the enhancement of strange particle yield in
nucleus-nucleus collisions is applied to study the singly and multiply strange
particle production in p-Pb and Pb-Pb collisions at 158A GeV/c. In this
mechanism the strange quark suppression factor is related to the effective
string tension, which increases in turn with the increase of the energy, of the
centrality and of the mass of colliding system. The WA97 observation that the
strange particle enhancement increases with the increasing of centrality and of
strange quark content in multiply strange particles in Pb-Pb collisions with
respect to p-Pb collisions was accounted reasonably.Comment: 8 pages, 3 PostScript figures, in Latex form. submitted to PR
Anti-Hyperon Enhancement through Baryon Junction Loops
The baryon junction exchange mechanism recently proposed to explain valence
baryon number transport in nuclear collisions is extended to study midrapidity
anti-hyperon production. Baryon junction-anti-junction (J anti-J) loops are
shown to enhance anti-Lambda, anti-Xi, anti-Omega yields as well as lead to
long range rapidity correlations. Results are compared to recent WA97 Pb + Pb
-> Y + anti-Y + X data.Comment: 10 pages, 4 figure
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