32,953 research outputs found
Publication patterns in HEP computing
An overview of the evolution of computing-oriented publications in high
energy physics following the start of operation of LHC. Quantitative analyses
are illustrated, which document the production of scholarly papers on
computing-related topics by high energy physics experiments and core tools
projects, and the citations they receive. Several scientometric indicators are
analyzed to characterize the role of computing in high energy physics
literature. Distinctive features of software-oriented and hardware-oriented
scholarly publications are highlighted. Current patterns and trends are
compared to the situation in previous generations' experiments.Comment: To be published in the Proc. of CHEP (Computing in High Energy
Physics) 201
Survey of EPA facilities for solar thermal energy applications
A study was done to assess the feasibility of applying solar thermal energy systems to EPA facilities. A survey was conducted to determine those EPA facilities where solar energy could best be used. These systems were optimized for each specific application and the system/facility combinations were ranked on the basis of greatest cost effectiveness
CPT, Lorentz invariance and anomalous clash of symmetries
In this paper we first discuss the analysis regarding the role of Lorentz
symmetry in the perturbative non-gravitational anomalies for a family of
fermions, which has been recently performed in arXiv:0809.0184. The theory is
assumed to be translational invariant, power-counting renormalizable and based
on a local action, but is allowed to have general Lorentz violating operators,
including those that break CPT. The main result is that Lorentz symmetry does
not participate in the clash of symmetries that leads to the anomalies.
Moreover, here we provide a simple "semiclassical" argument that shortly
illustrates the origin of this fact.Comment: 8 pages, no figures. To appear in the proceedings of Discrete '08:
Symposium on Prospects in the Physics of Discrete Symmetries, Valencia,
Spain, 11-16 Dec 200
Exact Quantum Solutions of Extraordinary N-body Problems
The wave functions of Boson and Fermion gases are known even when the
particles have harmonic interactions. Here we generalise these results by
solving exactly the N-body Schrodinger equation for potentials V that can be
any function of the sum of the squares of the distances of the particles from
one another in 3 dimensions. For the harmonic case that function is linear in
r^2. Explicit N-body solutions are given when U(r) = -2M \hbar^{-2} V(r) =
\zeta r^{-1} - \zeta_2 r^{-2}. Here M is the sum of the masses and r^2 = 1/2
M^{-2} Sigma Sigma m_I m_J ({\bf x}_I - {\bf x}_J)^2. For general U(r) the
solution is given in terms of the one or two body problem with potential U(r)
in 3 dimensions. The degeneracies of the levels are derived for distinguishable
particles, for Bosons of spin zero and for spin 1/2 Fermions. The latter
involve significant combinatorial analysis which may have application to the
shell model of atomic nuclei. For large N the Fermionic ground state gives the
binding energy of a degenerate white dwarf star treated as a giant atom with an
N-body wave function. The N-body forces involved in these extraordinary N-body
problems are not the usual sums of two body interactions, but nor are forces
between quarks or molecules. Bose-Einstein condensation of particles in 3
dimensions interacting via these strange potentials can be treated by this
method.Comment: 24 pages, Latex. Accepted for publication in Proceedings of the Royal
Societ
Relativistic Poynting Jets from Accretion Disks
A model is developed for relativistic Poynting jets from the inner region of
a disk around a rotating black hole. The disk is initially threaded by a
dipole-like magnetic field. The model is derived from the special relativistic
equation for a force-free electromagnetic field. The ``head'' of the Poynting
jet is found to propagate outward with a velocity which may be relativistic.
The Lorentz factor of the head (Gamma) is found to be dependent on the magnetic
field strength close to the black hole, B_0, the density of the external medium
n_ext, and on the ratio R=r_0/r_g >1, where r_g is the gravitational radius of
the black hole, and r_0 is the radius of the O-point of the initial dipole
field threading the disk. For conditions pertinent to an active galactic
nuclei, Gamma is approximately equal to 8 (10/R)^(1/3) (B_0/10^3 Gauss)^(1/3)
(1/cm^3/n_ext)^(1/6). This model offers an explanation for the observed Lorentz
factors which are of the order of 10 for the parsec-scale radio jets measured
with very long baseline interferometry.Comment: 4 pages, 1 figur
Qubit rotation and Berry Phase
A quantized fermion can be represented by a scalar particle encircling a
magnetic flux line. It has the spinor structure which can be constructed from
quantum gates and qubits. We have studied here the role of Berry phase in
removing dynamical phase during one qubit rotation of a quantized fermion. The
entanglement of two qubit inserting spin-echo to one of them results the change
of Berry phase that can be considered as a measure of entanglement. Some effort
is given to study the effect of noise on the Berry phase of spinor and their
entangled states.Comment: 12 page
Limit quantum efficiency for violation of Clauser-Horne Inequality for qutrits
In this paper we present the results of numerical calculations about the
minimal value of detection efficiency for violating the Clauser - Horne
inequality for qutrits. Our results show how the use of non-maximally entangled
states largely improves this limit respect to maximally entangled ones. A
stronger resistance to noise is also found.Comment: Phys. Rev. A in pres
Thermal entanglement of spins in a nonuniform magnetic field
We study the effect of inhomogeneities in the magnetic field on the thermal
entanglement of a two spin system. We show that in the ferromagnetic case a
very small inhomogeneity is capable to produce large values of thermal
entanglement. This shows that the absence of entanglement in the ferromagnetic
Heisenberg system is highly unstable against inhomogeneoity of magnetic fields
which is inevitably present in any solid state realization of qubits.Comment: 14 pages, 7 figures, latex, Accepted for publication in Physical
Review
Measurable nonlocal effect of bipartite system during a local cyclic evolution of its subsystem
In this letter, a nonlocal effect for a bipartite system which is induced by
a local cyclic evolution of one of its subsystem is suggested. This effect
vanishes when the system is at a disentangled pure state but can be observed
for some disentangled mixed states. As a paradigm, we study the effect for the
system of two qubits in detail. It is interesting that the effect is directly
related to the degree of entanglement for pure state of qubit pairs.
Furthermore, we suggest a Bell-type experiment to measure this nonlocal effect
for qubit pairs.Comment: 5 pages, 2 figure
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