1,426 research outputs found
Confining properties of 2-color QCD at finite density
We study the confining properties of QCD with two colors across the finite
density phase transition. A disorder parameter detecting dual superconductivity
of the QCD vacuum is used as a probe for the confinement/deconfinement phase
transition.Comment: 7 pages, 3 figures, talk presented at Lattice 2006 (High Temperature
and Density
GRB 140206A: the most distant polarized Gamma-Ray Burst
The nature of the prompt gamma-ray emission of Gamma-Ray Bursts (GRBs) is
still far from being completely elucidated. The measure of linear polarization
is a powerful tool that can be used to put further constraints on the content
and magnetization of the GRB relativistic outflows, as well as on the radiation
processes at work.
To date only a handful of polarization measurements are available for the
prompt emission of GRBs. Here we present the analysis of the prompt emission of
GRB 140206A, obtained with INTEGRAL/IBIS, Swift/BAT, and Fermi/GBM. Using
INTEGRAL/IBIS as a Compton polarimeter we were able to constrain the linear
polarization level of the second peak of this GRB as being larger than 28% at
90% c.l.
We also present the GRB afterglow optical spectroscopy obtained at the
Telescopio Nazionale Galileo (TNG), which allowed us the measure the distance
of this GRB, z=2.739. This distance value together with the polarization
measure obtained with IBIS, allowed us to derive the deepest and most reliable
limit to date (xi <1x10-16) on the possibility of Lorentz Invariance Violation,
measured through the vacuum birefringence effect on a cosmological source.Comment: 9 pages, 5 figures, 3 tables, accepted for publication in MNRAS.
arXiv admin note: text overlap with arXiv:1303.418
Non variability of intervening absorbers observed in the UVES spectra of the "naked-eye" GRB080319
The aim of this paper is to investigate the properties of the intervening
absorbers lying along the line of sight of Gamma-Ray Burst (GRB) 080319B
through the analysis of its optical absorption features. To this purpose, we
analyze a multi-epoch, high resolution spectroscopic observations (R=40000,
corresponding to 7.5 km/s) of the optical afterglow of GRB080319B (z=0.937),
taken with UVES at the VLT. Thanks to the rapid response mode (RRM), we
observed the afterglow just 8m:30s after the GRB onset when the magnitude was R
~ 12. This allowed us to obtain the best signal-to-noise, high resolution
spectrum of a GRB afterglow ever (S/N per resolution element ~ 50). Two further
RRM and target of opportunity observations were obtained starting 1.0 and 2.4
hours after the event, respectively. Four MgII absorption systems lying along
the line of sight to the afterglow have been detected in the redshift range 0.5
< z < 0.8, most of them showing a complex structure featuring several
components. Absorptions due to FeII, MgI and MnII are also present; they appear
in four, two and one intervening absorbers, respectively. One out of four
systems show a MgII2796 rest frame equivalent width larger than 1A. This
confirms the excess of strong MgII absorbers compared to quasars, with dn/dz =
0.9, ~ 4 times larger than the one observed along quasar lines of sight. In
addition, the analysis of multi-epoch, high-resolution spectra allowed us to
exclude a significant variability in the column density of the single
components of each absorber. Combining this result with estimates of the size
of the emitting region, we can reject the hypothesis that the difference
between GRB and QSO MgII absorbers is due to a different size of the emitting
regions.Comment: 10 pages, 15 ps figures, submitted to MNRA
UVES/VLT high resolution absorption spectroscopy of the GRB080330 afterglow: a study of the GRB host galaxy and intervening absorbers
We study the Gamma Ray Burst (GRB) environment and intervening absorbers by
analyzing the optical absorption features produced by gas surrounding the GRB
or along its line of sight. We analyzed high resolution spectroscopic
observations (R=40000, S/N=3 - 6) of the optical afterglow of GRB080330, taken
with UVES at the VLT ~ 1.5 hours after the GRB trigger. The spectrum
illustrates the complexity of the ISM of the GRB host galaxy at z = 1.51 which
has at least four components in the main absorption system. We detect strong
FeII, SiII, and NiII excited absorption lines associated with the bluemost
component only. In addition to the host galaxy, at least two more absorbers
lying along the line of sight to the afterglow have been detected in the
redshift range 0.8 < z < 1.1, each exhibiting MgII absorption. For the bluemost
component in the host galaxy, we derive information about its distance from the
site of the GRB explosion. We do so by assuming that the excited absorption
lines are produced by indirect UV pumping, and compare the data with a time
dependent photo-excitation code. The distance of this component is found to be
280+40-50 pc, which is lower than found for other GRBs (1 - 6 kpc). We identify
two additional MgII absorbers, one of them with a rest frame equivalent width
larger than 1A. The distance between the GRB and the absorber measured in this
paper confirms that the power of the GRB radiation can influence the conditions
of the interstellar medium up to a distance of at least several hundred pc. For
the intervening absorbers, we confirm the trend that on average one strong
intervening system is found per afterglow, as has been noted in studies
exhibiting an excess of strong MgII absorbers along GRB sightlines compared to
quasars.Comment: 8 Pages, 7 ps figures, A&A in pres
Confining Properties of Two-color QCD at Finite Density
We study the confining properties of QCD with two colors across the finite density phase transition. A disorder parameter detecting dual superconductivity of the QCD vacuum is used as a probe for the confinement/deconfinement phase transition
The institutional role of local associations in adopting a territorial knowledge management system within local systems
- …