859 research outputs found
Thermal monopoles and selfdual dyons in the Quark-Gluon Plasma
We perform a numerical study of the excess of non-abelian gauge invariant
gluonic action around thermal abelian monopoles which populate the deconfined
phase of Yang-Mills theories. Our results show that the excess of magnetic
action is close to that of the electric one, so that thermal abelian monopoles
may be associated with physical objects carrying both electric and magnetic
charge, i.e. dyons. Thus, the quark gluon plasma is likely to be populated by
selfdual dyons, which may manifest themselves in the heavy-ion collisions via
the chiral magnetic effect. Thermodynamically, thermal monopoles provide a
negative contribution to the pressure of the system.Comment: 9 pages, 4 figures, RevTeX 4.
A High Phase Advance Damped and Detuned Structure for the Main Linacs of Clic
The main accelerating structures for the CLIC are designed to operate at an
average accelerating gradient of 100 MV/m. The accelerating frequency has been
optimised to 11.994 GHz with a phase advance of 2{\pi}/3 of the main
accelerating mode. The moderately damped and detuned structure (DDS) design is
being studied as an alternative to the strongly damped WDS design. Both these
designs are based on the nominal accelerating phase advance. Here we explore
high phase advance (HPA) structures in which the group velocity of the rf
fields is reduced compared to that of standard (2{\pi}/3) structures. The
electrical breakdown strongly depends on the fundamental mode group velocity.
Hence it is expected that electrical breakdown is less likely to occur in the
HPA structures. We report on a study of both the fundamental and dipole modes
in a CLIC_DDS_HPA structure, designed to operate at 5{\pi}/6 phase advance per
cell. Higher order dipole modes in both the standard and HPA structures are
also studied
Enhanced coupling design of a detuned damped structure for clic
The key feature of the improved coupling design in the Damped Detuned
Structure (DDS) is focused on the four manifolds. Rectangular geometry slots
and rectangular manifolds are used. This results in a significantly stronger
coupling to the manifolds compared to the previous design. We describe the new
design together with its wakefield damping properties.Comment: 3 pages, 8 figures, submitted to IPAC1
Analysis of X-ray flares in GRBs
We present a detailed study of the spectral and temporal properties of the
X-ray flares emission of several GRBs. We select a sample of GRBs which X-ray
light curve exhibits large amplitude variations with several rebrightenings
superposed on the underlying three-segment broken powerlaw that is often seen
in Swift GRBs. We try to understand the origin of these fluctuations giving
some diagnostic in order to discriminate between refreshed shocks and late
internal shocks. For some bursts our time-resolved spectral analysis supports
the interpretation of a long-lived central engine, with rebrightenings
consistent with energy injection in refreshed shocks as slower shells generated
in the central engine prompt phase catch up with the afterglow shock at later
times.Comment: 9 pages, 3 figures. Invited talk at the Swift-Venice 2006 meeting to
be published by "Il Nuovo Cimento
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
X-Shooter spectroscopy of young stellar objects: V - Slow winds in T Tauri stars
Disks around T Tauri stars are known to lose mass, as best shown by the
profiles of forbidden emission lines of low ionization species. At least two
separate kinematic components have been identified, one characterised by
velocity shifts of tens to hundreds km/s (HVC) and one with much lower velocity
of few km/s (LVC). The HVC are convincingly associated to the emission of jets,
but the origin of the LVC is still unknown. In this paper we analyze the
forbidden line spectrum of a sample of 44 mostly low mass young stars in Lupus
and -Ori observed with the X-Shooter ESO spectrometer. We detect
forbidden line emission of [OI], [OII], [SII], [NI], and [NII], and
characterize the line profiles as LVC, blue-shifted HVC and red-shifted HVC. We
focus our study on the LVC. We show that there is a good correlation between
line luminosity and both L and the accretion luminosity (or the
mass-accretion rate) over a large interval of values (L L; L L;
M/yr). The lines show the presence of a slow
wind ( cm), warm (T K), mostly neutral. We estimate the mass of the emitting gas and
provide a value for the maximum volume it occupies. Both quantities increase
steeply with the stellar mass, from M and
AU for M M, to
M and AU for M M, respectively.
These results provide quite stringent constraints to wind models in low mass
young stars, that need to be explored further
The stiff Neumann problem: Asymptotic specialty and "kissing" domains
We study the stiff spectral Neumann problem for the Laplace operator in a smooth bounded domain Omega subset of R-d which is divided into two subdomains: an annulus Omega(1) and a core Omega(0). The density and the stiffness constants are of order epsilon(-2m) and epsilon(-1) in Omega(0), while they are of order 1 in( )Omega(1). Here m is an element of R is fixed and epsilon > 0 is small. We provide asymptotics for the eigenvalues and the corresponding eigenfunctions as epsilon -> 0 for any m. In dimension 2 the case when Omega(0) touches the exterior boundary partial derivative Omega S and Omega(1) gets two cusps at a point O is included into consideration. The possibility to apply the same asymptotic procedure as in the "smooth" case is based on the structure of eigenfunctions in the vicinity of the irregular part. The full asymptotic series as x -> O for solutions of the mixed boundary value problem for the Laplace operator in the cuspidal domain is given
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