6,802 research outputs found
Energy Dependence of High Moments for Net-proton Distributions
High moments of multiplicity distributions of conserved quantities are
predicted to be sensitive to critical fluctuations. To understand the effect of
the complicated non-critical physics backgrounds on the proposed observable, we
have studied various moments of net-proton distributions with AMPT, Hijing,
Therminator and UrQMD models, in which no QCD critical point physics is
implemented. It is found that the centrality evolution of various moments of
net-proton distributions can be uniformly described by a superposition of
emission sources. In addition, in the absence of critical phenomena, some
moment products of net-proton distribution, related to the baryon number
susceptibilities ratio in Lattice QCD calculation, are predicted to be constant
as a function of the collision centrality. We argue that a non-monotonic
dependence of the moment products as a function collision centrality and the
beam energy may be used to locate the QCD critical point.Comment: SQM2009 Proceeding, 6 pages, 5 figure
Structure of flame-made vanadia/titania and catalytic behaviour in the partial oxidation of o-xylene
Estimation of the particle-antiparticle correlation effect for pion production in heavy ion collisions
Estimation of the back-to-back pi-pi correlations arising due to evolution of
the pionic field in the course of pion production process is given for central
heavy nucleus collisions at moderate energies.Comment: 6 LaTeX pages + 5 ps figure
A fast search strategy for gravitational waves from low-mass X-ray binaries
We present a new type of search strategy designed specifically to find
continuously emitting gravitational wave sources in known binary systems based
on the incoherent sum of frequency modulated binary signal sidebands. The
search pipeline can be divided into three stages: the first is a wide
bandwidth, F-statistic search demodulated for sky position. This is followed by
a fast second stage in which areas in frequency space are identified as signal
candidates through the frequency domain convolution of the F-statistic with an
approximate signal template. For this second stage only precise information on
the orbit period and approximate information on the orbital semi-major axis are
required apriori. For the final stage we propose a fully coherent Markov chain
monte carlo based follow up search on the frequency subspace defined by the
candidates identified by the second stage. This search is particularly suited
to the low-mass X-ray binaries, for which orbital period and sky position are
typically well known and additional orbital parameters and neutron star spin
frequency are not. We note that for the accreting X-ray millisecond pulsars,
for which spin frequency and orbital parameters are well known, the second
stage can be omitted and the fully coherent search stage can be performed. We
describe the search pipeline with respect to its application to a simplified
phase model and derive the corresponding sensitivity of the search.Comment: 13 pages, 3 figures, to appear in the GWDAW 11 conference proceeding
The Post-Common Envelope and Pre-Cataclysmic Binary PG 1224+309
We have made extensive spectroscopic and photometric observations of PG
1224+309, a close binary containing a DA white dwarf primary and an M4+
secondary. The H alpha line is in emission due to irradiation of the M-star by
the hot white dwarf and is seen to vary around the orbit. From the radial
velocities of the H alpha line we derive a period of P = 0.258689 +/- 0.000004
days and a semi-amplitude of K_Halpha = 160 +/- 8 km/s. We estimate a
correction Delta_K = 21 +/- 2 km/s, where K_M = K_Halpha + Delta_K. Radial
velocity variations of the white dwarf reveal a semi-amplitude of K_WD = 112
+/- 14 km/s. The blue spectrum of the white dwarf is well fit by a synthetic
spectrum having T_eff = 29,300 K and log(g) = 7.38. The white dwarf contributes
97% of the light at 4500 Angstroms and virtually all of the light blueward of
3800 Angstroms. No eclipses are observed. The mass inferred for the white dwarf
depends on the assumed mass of the thin residual hydrogen envelope: 0.40 < M_WD
< 0.45 solar masses for hydrogen envelope masses of 0 < M_H < 4.0E-4 solar
masses. We argue that the mass of the white dwarf is closer to 0.45 solar
masses, hence it appears that the white dwarf has a relatively large residual
hydrogen envelope. The mass of the M-star is then M_M = 0.28 +/- 0.05 solar
masses, and the inclination is i = 77 +/- 7 degrees. We discuss briefly how PG
1224+309 may be used to constrain theories of close binary star evolution, and
the past and future histories of PG 1224+309 itself. The star is both a
``post-common envelope'' star and a ``pre-cataclysmic binary'' star. Mass
transfer by Roche-lobe overflow should commence in about 10 Gyr.Comment: 17 pages, 8 figures, AAS LaTeX, to appear in AJ, March 199
Anisotropic flow of strange particles at RHIC
Space-time picture of the anisotropic flow evolution in Au+Au collisions at
BNL RHIC is studied for strange hadrons within the microscopic quark-gluon
string model. The directed flow of both mesons and hyperons demonstrates wiggle
structure with the universal antiflow slope at |y| < 2 for minimum bias events.
This effect increases as the reaction becomes more peripheral. The development
of both components of the anisotropic flow is closely related to particle
freeze-out. Hadrons are emitted continuously, and different hadronic species
are decoupled from the system at different times. These hadrons contribute
differently to the formation and evolution of the elliptic flow, which can be
decomposed onto three components: (i) flow created by hadrons emitted from the
surface at the onset of the collision; (ii) flow produced by jets; (iii)
hydrodynamic flow. Due to these features, the general trend in elliptic flow
formation is that the earlier mesons are frozen, the weaker their elliptic
flow. In contrast, baryons frozen at the end of the system evolution have
stronger v2.Comment: proceedings of the conference SQM2004 (September 2004, Cape Town,
South Africa
Real-time data coupling for hybrid testing in a geotechnical centrifuge
Geotechnical centrifuge models necessarily involve simplifications compared to the full-scale scenario under investigation. In particular, structural systems (e.g. buildings or foundations) generally can’t be replicated such that complex full-scale characteristics are obtained. Hybrid testing offers the ability to combine capabilities from physical and numerical modelling to overcome some of the experimental limitations. In this paper, the development of a coupled centrifuge-numerical model (CCNM) pseudo-dynamic hybrid test for the study of tunnel-building interaction is presented. The methodology takes advantage of the relative merits of centrifuge tests (modelling soil behaviour and soil-pile interactions) and numerical simulations (modelling building deformations and load redistribution), with pile load and displacement data being passed in real-time between the two model domains. To appropriately model the full-scale scenario, a challenging force-controlled system was developed (the first of its kind for hybrid testing in a geotechnical centrifuge). The CCNM application can accommodate simple structural frame analyses as well as more rigorous simulations conducted using the finite element analysis software ABAQUS, thereby extending the scope of application to non-linear structural behaviour. A novel data exchange method between ABAQUS and LabVIEW is presented which provides a significant enhancement compared to similar hybrid test developments. Data are provided from preliminary tests which highlight the capabilities of the system to accurately model the global tunnel-building interaction problem
All Teleportation and Dense Coding Schemes
We establish a one-to-one correspondence between (1) quantum teleportation
schemes, (2) dense coding schemes, (3) orthonormal bases of maximally entangled
vectors, (4) orthonormal bases of unitary operators with respect to the
Hilbert-Schmidt scalar product, and (5) depolarizing operations, whose Kraus
operators can be chosen to be unitary. The teleportation and dense coding
schemes are assumed to be ``tight'' in the sense that all Hilbert spaces
involved have the same finite dimension d, and the classical channel involved
distinguishes d^2 signals. A general construction procedure for orthonormal
bases of unitaries, involving Latin Squares and complex Hadamard Matrices is
also presented.Comment: 21 pages, LaTe
Diskussion plastischer Instabilitäten eines Druckbehälters mit Hilfe der Methode der Finiten Elemente
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