3,691 research outputs found
Study of the Distillability of Werner States Using Entanglement Witnesses and Robust Semidefinite Programs
We use Robust Semidefinite Programs and Entanglement Witnesses to study the
distillability of Werner states. We perform exact numerical calculations which
show 2-undistillability in a region of the state space which was previously
conjectured to be undistillable. We also introduce bases which yield
interesting expressions for the {\em distillability witnesses} and for a tensor
product of Werner states with arbitrary number of copies.Comment: 16 pages, 2 figure
Subtropical Real Root Finding
We describe a new incomplete but terminating method for real root finding for
large multivariate polynomials. We take an abstract view of the polynomial as
the set of exponent vectors associated with sign information on the
coefficients. Then we employ linear programming to heuristically find roots.
There is a specialized variant for roots with exclusively positive coordinates,
which is of considerable interest for applications in chemistry and systems
biology. An implementation of our method combining the computer algebra system
Reduce with the linear programming solver Gurobi has been successfully applied
to input data originating from established mathematical models used in these
areas. We have solved several hundred problems with up to more than 800000
monomials in up to 10 variables with degrees up to 12. Our method has failed
due to its incompleteness in less than 8 percent of the cases
On the Nodal Count Statistics for Separable Systems in any Dimension
We consider the statistics of the number of nodal domains aka nodal counts
for eigenfunctions of separable wave equations in arbitrary dimension. We give
an explicit expression for the limiting distribution of normalised nodal counts
and analyse some of its universal properties. Our results are illustrated by
detailed discussion of simple examples and numerical nodal count distributions.Comment: 21 pages, 4 figure
On the Invariant Theory of Weingarten Surfaces in Euclidean Space
We prove that any strongly regular Weingarten surface in Euclidean space
carries locally geometric principal parameters. The basic theorem states that
any strongly regular Weingarten surface is determined up to a motion by its
structural functions and the normal curvature function satisfying a geometric
differential equation. We apply these results to the special Weingarten
surfaces: minimal surfaces, surfaces of constant mean curvature and surfaces of
constant Gauss curvature.Comment: 16 page
Extraction of the electron mass from factor measurements on light hydrogenlike ions
The determination of the electron mass from Penning-trap measurements with
C ions and from theoretical results for the bound-electron
factor is described in detail. Some recently calculated contributions slightly
shift the extracted mass value. Prospects of a further improvement of the
electron mass are discussed both from the experimental and from the theoretical
point of view. Measurements with He ions will enable a consistency
check of the electron mass value, and in future an improvement of the He
nuclear mass and a determination of the fine-structure constant
Comparing Chandra and SIRTF Observations for Obscured Starbursts and AGN at High Redshift
Tracking the star formation rate to high redshifts requires knowledge of the
contribution from both optically visible and obscured sources. The dusty,
optically-obscured galaxies can be located by X-ray and infrared surveys. To
establish criteria for selecting such sources based only on X-ray and infrared
surveys, we determine the ratio of infrared to X-ray brightness that would be
observed by SIRTF and Chandra for objects with the same spectral shapes as
nearby starbursts if seen at high redshift. The parameter IR/X is defined as
IR/X = (flux density observed in SIRTF MIPS 24 m filter in mJy)/(total
flux observed within 0.5-2.0 keV in units of 10^-16 ergs\s\cm^2). Based on
observations of NGC 4038/39 (``The Antennae''), NGC 3690+IC 694 (Arp 299 or Mkn
171), M 82, and Arp 220, nine starburst regions are compared using mid-infrared
spectra taken by the Infrared Space Observatory (ISO) and X-ray spectra
obtained with Chandra . The IR/X are determined as they would appear for 1<z<3.
The mean IR/X over this redshift range is 1.3 and is not a significant function
of redshift or luminosity, indicating that SIRTF surveys reaching 0.4 mJy at 24
m should detect the same starbursts as deep CXO surveys detect at a flux
of 0.3x10^-16 ergs/s/cm^2. The lower bound of IR/X for starbursts is about 0.2,
suggesting that objects with IR/X smaller than this have an AGN X-ray component
in addition to the starburst. Values of IR/X for the obscured AGN within NGC
1068, the Circinus galaxy, and NGC 6240 are also determined for comparison
although interpretation is complicated by the circumnuclear starbursts in these
galaxies. Any sources found in surveys having IR/X>4 would not match any of the
objects considered.Comment: accepted for publication in Ap
The [CII] 158 um Line Deficit in Ultraluminous Infrared Galaxies Revisited
We present a study of the [CII] 157.74 um fine-structure line in a sample of
15 ultraluminous infrared (IR) galaxies (L_IR>10^12 Lsun; ULIRGs) using the
Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). We
confirm the observed order of magnitude deficit (compared to normal and
starburst galaxies) in the strength of the [CII] line relative to the far-IR
dust continuum emission found in our initial report (Luhman et al. 1998), but
here with a sample that is twice as large. This result suggests that the
deficit is a general phenomenon affecting 4/5 ULIRGs. We present an analysis
using observations of generally acknowledged photodissociation region (PDR)
tracers ([CII], [OI] 63 and 145 um, and FIR continuum emission), which suggests
that a high UV flux G_o incident on a moderate density n PDR could explain the
deficit. However, comparisons with other ULIRG observations, including CO
(1-0), [CI] (1-0), and 6.2 um polycyclic aromatic hydrocarbon (PAH) emission,
suggest that high G_o/n PDRs alone cannot produce a self-consistent solution
that is compatible with all of the observations. We propose that non-PDR
contributions to the FIR continuum can explain the apparent [CII] deficiency.
Here, unusually high G_o and/or n physical conditions in ULIRGs as compared to
those in normal and starburst galaxies are not required to explain the [CII]
deficit. Dust-bounded photoionization regions, which generate much of the FIR
emission but do not contribute significant [CII] emission, offer one possible
physical origin for this additional non-PDR component. Such environments may
also contribute to the observed suppression of FIR fine-structure emission from
ionized gas and PAHs, as well as the warmer FIR colors found in ULIRGs. The
implications for observations at higher redshifts are also revisited.Comment: to be published in The Astrophysical Journal, 58 page
Analysis of kaon spectra at SIS energies - what remains from the KN potential
We study the reaction Au+Au at 1.48 AGeV and analyze the influence of the KN
optical potential on cm spectra and azimuthal distributions at mid-rapidity. We
find a significant change of the yields but only slight changes in the shapes
of the distributions when turning off the optical potential. However, the
spectra show contributions from different reaction times, where early kaons
contribute stronger to higher momenta and late kaons to lower momenta.
Azimuthal distributions of the kaons at mid-rapidity show a strong centrality
dependence. Their shape is influenced by the KN optical potential as well as by
re-scattering.Comment: SQM 2003 proceedings, 4 figures, 6 page
Prototype design of a timing and fast control system in the CBM experiment
The Compressed Baryonic Matter (CBM) experiment is designed to handle interaction rates of up to 10 MHz and up to 1 TB/s of raw data generated. With triggerless streaming data acquisition in the experiment and beam intensity fluctuations, it is expected that occasional data bursts will surpass bandwidth capabilities of the Data Acquisition System (DAQ) system. In order to preserve integrity of event data, the bandwidth of DAQ must be throttled in an organised way with minimum information loss. The Timing and Fast Control (TFC) system provides a latency-optimised datapath for throttling commands and distributes a system clock together with a global timestamp. This paper describes a prototype design of the system with focus on synchronisation and its evaluation
Prototype design of a timing and fast control system in the CBM experiment
The Compressed Baryonic Matter (CBM) experiment is designed to handle interaction rates of up to 10 MHz and up to 1 TB/s of raw data generated. With triggerless streaming data acquisition in the experiment and beam intensity fluctuations, it is expected that occasional data bursts will surpass bandwidth capabilities of the Data Acquisition System (DAQ) system. In order to preserve integrity of event data, the bandwidth of DAQ must be throttled in an organised way with minimum information loss. The Timing and Fast Control (TFC) system provides a latency-optimised datapath for throttling commands and distributes a system clock together with a global timestamp. This paper describes a prototype design of the system with focus on synchronisation and its evaluation
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