791 research outputs found
Suboptimal quantum-error-correcting procedure based on semidefinite programming
In this paper, we consider a simplified error-correcting problem: for a fixed
encoding process, to find a cascade connected quantum channel such that the
worst fidelity between the input and the output becomes maximum. With the use
of the one-to-one parametrization of quantum channels, a procedure finding a
suboptimal error-correcting channel based on a semidefinite programming is
proposed. The effectiveness of our method is verified by an example of the
bit-flip channel decoding.Comment: 6 pages, no figure, Some notations differ from those in the PRA
versio
Relativistic dissipative hydrodynamics with extended matching conditions for ultra-relativistic heavy-ion collisions
Recently we proposed a novel approach to the formulation of relativistic
dissipative hydrodynamics by extending the so-called matching conditions in the
Eckart frame [Phys. Rev. {\bf C 85}, (2012) 14906]. We extend this formalism
further to the arbitrary Lorentz frame. We discuss the stability and causality
of solutions of fluid equations which are obtained by applying this formulation
to the Landau frame, which is more relevant to treat the fluid produced in
ultra-relativistic heavy-ion collisions. We derive equations of motion for a
relativistic dissipative fluid with zero baryon chemical potential and show
that linearized equations obtained from them are stable against small
perturbations. It is found that conditions for a fluid to be stable against
infinitesimal perturbations are equivalent to imposing restrictions that the
sound wave, , propagating in the fluid, must not exceed the speed of light
, i.e., . This conclusion is equivalent to that obtained in the
previous paper using the Eckart frame [Phys. Rev. {\bf C 85}, (2012) 14906].Comment: 2nd version. Typos corrected. 7 pages. Contribution to The European
Physical Journal A (Hadrons and Nuclei) topical issue about 'Relativistic
Hydro- and Thermodynamics in Nuclear Physics
On Witten multiple zeta-functions associated with semisimple Lie algebras IV
In our previous work, we established the theory of multi-variable Witten
zeta-functions, which are called the zeta-functions of root systems. We have
already considered the cases of types , , , and . In
this paper, we consider the case of -type. We define certain analogues of
Bernoulli polynomials of -type and study the generating functions of them
to determine the coefficients of Witten's volume formulas of -type. Next
we consider the meromorphic continuation of the zeta-function of -type and
determine its possible singularities. Finally, by using our previous method, we
give explicit functional relations for them which include Witten's volume
formulas.Comment: 22 pag
Structure formation in the presence of relativistic heat conduction: corrections to the Jeans wave number with a stable first order in the gradients formalism
The problem of structure formation in relativistic dissipative fluids was
analyzed in a previous work within Eckart's framework, in which the heat flux
is coupled to the hydrodynamic acceleration, additional to the usual
temperature gradient term. It was shown that in such case, the pathological
behavior of fluctuations leads to the disapperance of the gravitational
instability responsible for structure formation. In the present work the
problem is revisited now using a constitutive equation derived from
relativistic kinetic theory. The new relation, in which the heat flux is not
coupled to the hydrodynamic acceleration, leads to a consistent first order in
the gradients formalism. In this case the gravitational instability remains,
and only relativistic corrections to the Jeans wave number are obtained. In the
calculation here shown the non-relativistc limit is recovered, opposite to what
happens in Eckart's case.Comment: 10 pages, no figure
The Cosmic Infrared Background Experiment (CIBER): Instrumentation and First Results
Ultraviolet emission from the first generation of stars in the Universe ionized the intergalactic medium in a process which was completed by z similar to 6; the wavelength of these photons has been redshifted by (1 + z) into the near infrared today and can be measured using instruments situated above the Earth's atmosphere. First flying in February 2009, the Cosmic Infrared Background ExpeRiment (CIBER) comprises four instruments housed in a single reusable sounding rocket borne payload. CIBER will measure spatial anisotropies in the extragalactic IR background caused by cosmological structure from the epoch of reionization using two broadband imaging instruments, make a detailed characterization of the spectral shape of the IR background using a low resolution spectrometer, and measure the absolute brightness of the Zodiacal light foreground with a high resolution spectrometer in each of our six science fields. The scientific motivation for CIBER and details of its first and second flight instrumentation will be discussed. First flight results on the color of the zodiacal light around 1 mu m and plans for the future will also be presented
Observations of the Near-infrared Spectrum of the Zodiacal Light with CIBER
Interplanetary dust (IPD) scatters solar radiation which results in the zodiacal light that dominates the celestial diffuse brightness at optical and near-infrared wavelengths. Both asteroid collisions and cometary ejections produce the IPD, but the relative contribution from these two sources is still unknown. The low resolution spectrometer (LRS) onboard the Cosmic Infrared Background ExpeRiment (CIBER) observed the astrophysical sky spectrum between 0.75 and 2.1 μm over a wide range of ecliptic latitude. The resulting zodiacal light spectrum is redder than the solar spectrum, and shows a broad absorption feature, previously unreported, at approximately 0.9 μm, suggesting the existence of silicates in the IPD material. The spectral shape of the zodiacal light is isotropic at all ecliptic latitudes within the measurement error. The zodiacal light spectrum, including the extended wavelength range to 2.5 μm using Infrared Telescope in Space (IRTS) data, is qualitatively similar to the reflectance of S-type asteroids. This result can be explained by the proximity of S-type asteroidal dust to Earth's orbit, and the relatively high albedo of asteroidal dust compared with cometary dust
Spitzer Observations of the North Ecliptic Pole
We present a photometric catalog for Spitzer Space Telescope warm mission
observations of the North Ecliptic Pole (NEP; centered at , ). The observations are
conducted with IRAC in 3.6 m and 4.5 m bands over an area of 7.04
deg reaching 1 depths of 1.29 Jy and 0.79 Jy in the 3.6
m and 4.5 m bands respectively. The photometric catalog contains
380,858 sources with 3.6 m and 4.5 m band photometry over the
full-depth NEP mosaic. Point source completeness simulations show that the
catalog is 80% complete down to 19.7 AB. The accompanying catalog can be
utilized in constraining the physical properties of extra-galactic objects,
studying the AGN population, measuring the infrared colors of stellar objects,
and studying the extra-galactic infrared background light.Comment: 10 pages, 11 figures and 3 tables. Accepted to the ApJ
Dissipative or just Nonextensive hydrodynamics? - Nonextensive/Dissipative correspondence -
We argue that there is correspondence between the perfect nonextensive
hydrodynamics and the usual dissipative hydrodynamics, which we call
nonextensive/dissipative correspondence (NexDC). It leads to simple expression
for dissipative entropy current and allows for predictions for the ratio of
bulk and shear viscosities to entropy density, and .Comment: 4 pages, 2 figures, presented as poster at QM2008 conference at
Jaipur; will be published by Indian Journal of Physic
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