7,137 research outputs found
Ultra high energy events in ECHOS series and primary energy spectrum
The compilation of ultra high energy jets suggests at present the existence of a bump in primary energy spectrum (with the standard concept of high energy collisions). The pseudo-rapidity distribution exhibits some typical anomalies, more than the (P sub t) behavior, which are (may be) the fingerprints of quark gluon plasma transition. The next results of Emulsion Chamber on Supersonic (ECHOS) will be in both cases determinant to confirm those tendancies, as well as an important effort of the cosmic ray community to develop in that sense a flying emulsion chamber experiment
Evolution of iron core white dwarfs
Recent measurements made by Hipparcos (Provencal et al. 1998) present
observational evidence supporting the existence of some white dwarf (WD) stars
with iron - rich, core composition. In this connection, the present paper is
aimed at exploring the structure and evolution of iron - core WDs by means of a
detailed and updated evolutionary code. In particular, we examine the evolution
of the central conditions, neutrino luminosity, surface gravity,
crystallization, internal luminosity profiles and ages. We find that the
evolution of iron - rich WDs is markedly different from that of their carbon -
oxygen counterparts. In particular, cooling is strongly accelerated as compared
with the standard case. Thus, if iron WDs were very numerous, some of them
would have had time enough to evolve at lower luminosities than that
corresponding to the fall - off in the observed WD luminosity function.Comment: 8 pages, 21 figures. Accepted for publication in MNRA
Spin-Gap Phase in the One-Dimensional t-J-J' Model
The spin-gap phase of the one-dimensional t-J-J' model is studied by the
level-crossing of the singlet and the triplet excitation spectra.
The phase boundary obtained between the Tomonaga-Luttinger and the spin-gap
phases is remarkably consistent with the analytical results at the
and the low-density limits discussed by Ogata et al.
The spin-gap phase has a single domain in the phase diagram even if the spin
gap opens at half-filling.
The phase boundary coincides with the line where the
Tomonaga-Luttinger liquid behaves as free electrons, in the low-density region.
The relation between our method and the solution of the two-electron problem
is also discussed.Comment: 4 pages(JPSJ.sty), 5 figures(EPS), to appear in J. Phys. Soc. Jpn.
67, No.3 (1998
Hierarchy of Temporal Responses of Multivariate Self-Excited Epidemic Processes
We present the first exact analysis of some of the temporal properties of
multivariate self-excited Hawkes conditional Poisson processes, which
constitute powerful representations of a large variety of systems with bursty
events, for which past activity triggers future activity. The term
"multivariate" refers to the property that events come in different types, with
possibly different intra- and inter-triggering abilities. We develop the
general formalism of the multivariate generating moment function for the
cumulative number of first-generation and of all generation events triggered by
a given mother event (the "shock") as a function of the current time . This
corresponds to studying the response function of the process. A variety of
different systems have been analyzed. In particular, for systems in which
triggering between events of different types proceeds through a one-dimension
directed or symmetric chain of influence in type space, we report a novel
hierarchy of intermediate asymptotic power law decays of the rate of triggered events as a function of the
distance of the events to the initial shock in the type space, where for the relevant long-memory processes characterizing many natural
and social systems. The richness of the generated time dynamics comes from the
cascades of intermediate events of possibly different kinds, unfolding via a
kind of inter-breeding genealogy.Comment: 40 pages, 8 figure
Invariant manifolds and orbit control in the solar sail three-body problem
In this paper we consider issues regarding the control and orbit transfer of solar sails in the circular restricted Earth-Sun system. Fixed points for solar sails in this system have the linear dynamical properties of saddles crossed with centers; thus the fixed points are dynamically unstable and control is required. A natural mechanism of control presents itself: variations in the sail's orientation. We describe an optimal controller to control the sail onto fixed points and periodic orbits about fixed points. We find this controller to be very robust, and define sets of initial data using spherical coordinates to get a sense of the domain of controllability; we also perform a series of tests for control onto periodic orbits. We then present some mission strategies involving transfer form the Earth to fixed points and onto periodic orbits, and controlled heteroclinic transfers between fixed points on opposite sides of the Earth. Finally we present some novel methods to finding periodic orbits in circumstances where traditional methods break down, based on considerations of the Center Manifold theorem
Effects of instillation locations of boulders at bottom of pool-and-weir fishway on migration rate of Zacco platypus
It is important to keep suitable area by boulders in pooland- weir fishway to make the migration rate of fish high. In this study, migrating behaviors of Zacco platypus in pooland- weir fishway were compared with locations of boulders placed on the bottom of pool-and-weir fishway changed. Migration behaviors of Zacco platypus were obtained with the aid of two digital video cameras. It was found that Zacco platypus migrates remarkably uses the space between boulders when boulders were placed on the upper bottom in the pool. It is because the velocity of space between boulders is low compared to other space.The 11th Pacific Symposium on Flow Visualization and Image Processing, 2017, 1-3 December, Kumamoto, Japa
Apparent Clustering and Apparent Background Earthquakes Biased by Undetected Seismicity
In models of triggered seismicity and in their inversion with empirical data,
the detection threshold m_d is commonly equated to the magnitude m_0 of the
smallest triggering earthquake. This unjustified assumption neglects the
possibility of shocks below the detection threshold triggering observable
events. We introduce a formalism that distinguishes between the detection
threshold m_d and the minimum triggering earthquake m_0 < m_d. By considering
the branching structure of one complete cascade of triggered events, we derive
the apparent branching ratio n_a (which is the apparent fraction of aftershocks
in a given catalog) and the apparent background source S_a that are observed
when only the structure above the detection threshold m_d is known due to the
presence of smaller undetected events that are capable of triggering larger
events. If earthquake triggering is controlled in large part by the smallest
magnitudes as several recent analyses have shown, this implies that previous
estimates of the clustering parameters may significantly underestimate the true
values: for instance, an observed fraction of 55% of aftershocks is
renormalized into a true value of 75% of triggered events.Comment: 12 pages; incl. 6 Figures, AGU styl
Effective radii of deuteron induced reactions
The continuum-discretized coupled-channels method (CDCC) for exclusive
reactions and the eikonal reaction theory (ERT) as an extension of CDCC to
inclusive reactions are applied to deuteron induced reactions. The CDCC result
reproduces experimental data on the reaction cross section for Ni
scattering at 200 MeV/nucleon and ERT does data on the neutron-stripping cross
section for inclusive Li reaction at 40 MeV. For deuteron induced
reactions at 200 MeV/nucleon, target-dependence of the reaction,
elastic-breakup, nucleon-stripping, nucleon-removal, complete- and
incomplete-fusion cross sections is clearly explained by simple formulae.
Accuracy of the Glauber model is also investigated.Comment: 11 pages, 11 figures, 2 table
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