668,484 research outputs found
Strangeness Balance in HADES Experiments and the Xi- Enhancement
HADES data on a strangeness production in Ar+KCl collisions at 1.76A GeV are
analyzed within a minimal statistical model. The total negative strangeness
content is fixed by the observed K^+ multiplicities on event-by-event basis.
Particles with negative strangeness are assumed to remain in chemical
equilibrium with themselves and in thermal equilibrium with the environment
until a common freeze-out. Exact strangeness conservation in each collision
event is explicitly preserved. This implies that Xi baryons can be released
only in events where two or more kaons are produced. An increase of the
fireball volume due to application of a centrality trigger in HADES experiments
is taken into account. We find that experimental ratios of K-/K+, Lambda/K+ and
Sigma/K+ can be satisfactorily described provided in-medium potentials are
taken into account. However, the calculated Xi-/Lambda/K+ ratio proves to be
significantly smaller compared to the measured value (8 times lower than the
experimental median value and 3 times lower than the lower error bar). Various
scenarios to explain observed Xi enhancement are discussed. Arguments are given
in favor of the Xi production in direct reactions. The rates of the possible
production processes are estimated and compared.Comment: 13 pages, 3 figure
Comment on "Transverse Force on a Quantized Vortex in a Superfluid"
The result of Thouless, Ao and Niu (TAN), that the mutual friction parameter
, contradicts to the experiments made in rotating 3He-B by
Manchester group. The Manchester group observed that at low
temperature and approaches 1 at high temperature. The reason of the
contradiction is that TAN did not take into account the Iordanskii force on the
vortex and the spectral flow force, which comes from the anomaly related to the
low-energy bound states of fermions in cores of quantized vortices. The
Iordanskii force is responsible for the negative at low
temperature, while due to the spectral flow approaches 1 at high
temperature. Relation of the spectral flow anomaly with the paradoxes of the
linear and angular momenta in gapless superfluids is discussed.Comment: revtex, 2 pages, submitted to Physical Review Letters as "Comment" to
the paper D.J. Thouless, P. Ao and Q. Niu, Phys. Rev. Lett. 76, 3758 (1996
From Light Nuclei to Nuclear Matter. The Role of Relativity?
The success of non-relativistic quantum dynamics in accounting for the
binding energies and spectra of light nuclei with masses up to A=10 raises the
question whether the same dynamics applied to infinite nuclear matter agrees
with the empirical saturation properties of large nuclei.The simple unambiguous
relation between few-nucleon and many-nucleon Hamiltonians is directly related
to the Galilean covariance of nonrelativistic dynamics. Relations between the
irreducible unitary representations of the Galilei and Poincare groups indicate
thatthe ``nonrelativistic'' nuclear Hamiltonians may provide sufficiently
accurate approximations to Poincare invariant mass operators. In relativistic
nuclear dynamics based on suitable Lagrangeans the intrinsic nucleon parity is
an explicit, dynamically relevant, degree of freedom and the emphasis is on
properties of nuclear matter. The success of this approach suggests the
question how it might account for the spectral properties of light nuclei.Comment: conference proceedings "The 11th International Conference on Recent
Progress in Many-Body Theories" to be published by World Scientifi
Slow solitary waves in multi-layered magnetic structures
The propagation of slow sausage surface waves in a multi-layered magnetic configuration is considered. The magnetic configuration consists of a central magnetic slab sandwiched between two identical magnetic slabs (with equilibrium quantities different from those in the central slab) which in turn are embedded between two identical semi-infinite regions. The dispersion equation is obtained in the linear approximation. The nonlinear governing equation describing waves with a characteristic wavelength along the central slab much larger than the slab thickness is derived. Solitary wave solutions to this equation are obtained in the case where these solutions deviate only slightly from the algebraic soliton of the Benjamin-Ono equation
Rotating vortex core: An instrument for detecting the core excitations
Effects of fermionic zero modes (bound states in a vortex core) on the
rotational dynamics of vortices with sponaneously broken axisymmetry are
considered. The results are compared with the Helsinki experiments where the
vortex cores were driven to a fast rotation and torsional oscillations by an
NMR r.f. field (Kondo et al, Phys. Rev. Lett. 67, 81 (1991)). We predict a
resonance NMR absorption on localized states at the external frequency
comparable with the interelevel distance, which is similar to the cyclotron
Landau damping. The resonances can experimentally resolve the localized levels
in vortex cores. For a pure rotation of the core, the effect depends on the
relative signs of the vortex winding number and of the core rotation; thus it
is sensitive to the direction of rotation of the container. The similarity with
the fermionic zero modes on the fundamental strings, which simulate the
thermodynamics of black holes, is discussed.Comment: RevTex file, 7 pages, 1 Figure, extended and clarified after referee
Reports, to appear in Phys. Rev.
Fermionic determinant for dyons and instantons with nontrivial holonomy
We calculate exactly the functional determinant for fermions in fundamental
representation of SU(2) in the background of periodic instanton with
non-trivial value of the Polyakov line at spatial infinity. The determinant
depends on the value of the holonomy v, the temperature, and the parameter
r_12, which at large values can be treated as separation between the
Bogomolny--Prasad--Sommerfeld monopoles (or dyons) which constitute the
periodic instanton. We find a compact expression for small and large r_12 and
compute the determinant numerically for arbitrary r_12 and v.Comment: 17 pages, published version, references adde
Dynamic vortex mass in clean Fermi superfluids and superconductors
We calculate the dynamic vortex mass for clean Fermi superfluids including
both s- and d-wave superconductors as a response to a vortex acceleration.
Assuming a finite quasiparticle mean free time, the vortex mass appears to be a
tensor. The diagonal component dominates in the limit of long mean free time
while the off-diagonal mass takes over in the moderately clean regime.Comment: 4 pages, no figures, typeset using RevTe
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