1,772 research outputs found
The mass of X-Ray Nova Scorpii 1994 (=GRO J1655--40)]
We have obtained high and intermediate resolution optical spectra of the
black-hole candidate Nova Sco 1994 in May/June 1998, when the source was in
complete (X-ray) quiescence. We measure the radial velocity curve of the
secondary star and obtain a semi-amplitude of K_2=215.5+/-2.4 km/s, which is 6
per cent lower than the only previously determined value. This new value for
K_2 thus reduces the binary mass function to f(M) = 2.73+/-0.09 Mo. Using only
the high resolution spectra we constrain the rotational broadening of the
secondary star, vsini, to lie in the range 82.9-94.9 km/s (95 per cent
confidence) and thus constrain the binary mass ratio to lie in the range
0.337--0.436 (95 per cent confidence). We can also combine our results with
published limits for the binary inclination to constrain the mass of the
compact object and secondary star to the ranges 5.5 -- 7.9 and 1.7 -- 3.3 Mo
respectively (95 per cent confidence). Finally, we report on the detection of
the Lithium resonance line at 6707.8 A, with an equivalent width of 55+/-8 mA.Comment: 5 pages, 5 figures, accepted by MNRA
Development of a high-throughput microsatellite typing approach for forensic and population genetic analysis of wild and domestic African Bovini
Conservation management and forensic traceability of African buffalo and cattle rely on the timely provision of unbiased and accurate genetic information. An approach in which 17 cattle microsatellite markers are co-electrophoresed, following amplification in three core multiplex reactions was established for this purpose. Mean allelic richness per locus was 8.24 and 6.47, for buffalo and Bonsmara cattle, respectively, whilst an unbiased match probability of 6.5xĂ—10-17 and 1.03 Ă— 10-16 was obtained for each. These results confirm the usefulness of this rapid, cost-effective typing approach for forensic, paternity and fine-scale genetic analyses of wild and domestic African Bovini tribe member
Numerical study of Yang-Mills classical solutions on the twisted torus
We use the lattice cooling method to investigate the structure of some gauge
fixed SU(2) Yang-Mills classical solutions of the euclidean equations of motion
which are defined in the 3-torus with symmetric twisted boundary conditions.Comment: 20pp (fig.included
Observation of Goos-H\"{a}nchen shifts in metallic reflection
We report the first observation of the Goos-Hnchen
shift of a light beam incident on a metal surface. This phenomenon is
particularly interesting because the Goos-Hnchen shift
for polarized light in metals is negative and much bigger than the positive
shift for polarized light. The experimental result for the measured shifts
as a function of the angle of incidence is in excellent agreement with
theoretical predictions. In an energy-flux interpretation, our measurement
shows the existence of a backward energy flow at the bare metal surface when
this is excited by a polarized beam of light.Comment: The parer was published on Optics Express. The new version is
modified according to the reviewers suggestion
Ms2lda.org: web-based topic modelling for substructure discovery in mass spectrometry
Motivation: We recently published MS2LDA, a method for the decomposition of sets of molecular fragment data derived from large metabolomics experiments. To make the method more widely available to the community, here we present ms2lda.org, a web application that allows users to upload their data, run MS2LDA analyses and explore the results through interactive visualisations.
Results: Ms2lda.org takes tandem mass spectrometry data in many standard formats and allows the user to infer the sets of fragment and neutral loss features that co-occur together (Mass2Motifs). As an alternative workflow, the user can also decompose a dataset onto predefined Mass2Motifs. This is accomplished through the web interface or programmatically from our web service
Four dimensional R^4 superinvariants through gauge completion
We fully compute the N=1 supersymmetrization of the fourth power of the Weyl
tensor in d=4 x-space with the auxiliary fields. In a previous paper, we showed
that their elimination requires an infinite number of terms; we explicitely
compute those terms to order \kappa^4 (three loop). We also write, in
superspace notation, all the possible N=1 actions, in four dimensions, that
contain pure R^4 terms (with coupling constants). We explicitely write these
actions in terms of the \theta components of the chiral density \epsilon and
the supergravity superfields R, G_m, W_{ABC}. Using the method of gauge
completion, we compute the necessary \theta components which allow us to write
these actions in x-space. We discuss under which circumstances can these extra
R^4 correction terms be reabsorbed in the pure supergravity action, and their
relevance to the quantum supergravity/string theory effective actions.Comment: 20 pages, no figures. Sec. 3 clarified; typos correcte
Probing for Instanton Quarks with epsilon-Cooling
We use epsilon-cooling, adjusting at will the order a^2 corrections to the
lattice action, to study the parameter space of instantons in the background of
non-trivial holonomy and to determine the presence and nature of constituents
with fractional topological charge at finite and zero temperature for SU(2). As
an additional tool, zero temperature configurations were generated from those
at finite temperature with well-separated constituents. This is achieved by
"adiabatically" adjusting the anisotropic coupling used to implement finite
temperature on a symmetric lattice. The action and topological charge density,
as well as the Polyakov loop and chiral zero-modes are used to analyse these
configurations. We also show how cooling histories themselves can reveal the
presence of constituents with fractional topological charge. We comment on the
interpretation of recent fermion zero-mode studies for thermalized ensembles at
small temperatures.Comment: 26 pages, 14 figures in 33 part
A class of elementary particle models without any adjustable real parameters
Conventional particle theories such as the Standard Model have a number of
freely adjustable coupling constants and mass parameters, depending on the
symmetry algebra of the local gauge group and the representations chosen for
the spinor and scalar fields. There seems to be no physical principle to
determine these parameters as long as they stay within certain domains dictated
by the renormalization group. Here however, reasons are given to demand that,
when gravity is coupled to the system, local conformal invariance should be a
spontaneously broken exact symmetry. The argument has to do with the
requirement that black holes obey a complementarity principle relating ingoing
observers to outside observers, or equivalently, initial states to final
states. This condition fixes all parameters, including masses and the
cosmological constant. We suspect that only examples can be found where these
are all of order one in Planck units, but the values depend on the algebra
chosen. This paper combines findings reported in two previous preprints, and
puts these in a clearer perspective by shifting the emphasis towards the
implications for particle models.Comment: 28 pages (incl. title page), no figure
On the stability of Dirac sheet configurations
Using cooling for SU(2) lattice configurations, purely Abelian constant
magnetic field configurations were left over after the annihilation of
constituents that formed metastable Q=0 configurations. These so-called Dirac
sheet configurations were found to be stable if emerging from the confined
phase, close to the deconfinement phase transition, provided their Polyakov
loop was sufficiently non-trivial. Here we show how this is related to the
notion of marginal stability of the appropriate constant magnetic field
configurations. We find a perfect agreement between the analytic prediction for
the dependence of stability on the value of the Polyakov loop (the holonomy) in
a finite volume and the numerical results studied on a finite lattice in the
context of the Dirac sheet configurations
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