100,730 research outputs found
A coordinate-dependent superspace deformation from string theory
Starting from a type II superstring model defined on in
a linear graviphoton background, we derive a coordinate dependent -deformed
, superspace. The chiral fermionic coordinates
satisfy a Clifford algebra, while the other coordinate algebra remains
unchanged. We find a linear relation between the graviphoton field strength and
the deformation parameter. The null coordinate dependence of the graviphoton
background allows to extend the results to all orders in .Comment: 14 pages, reference added, accepted for publication in JHE
Exact partition function in ABJM theory deformed by mass and Fayet-Iliopoulos terms
We exactly compute the partition function for ABJM
theory on deformed by mass and Fayet-Iliopoulos parameter
. For , the partition function has an infinite number of
Lee-Yang zeros. For general , in the decompactification limit the theory
exhibits a quantum (first-order) phase transition at .Comment: 11 pages, 1 figure. v2: references adde
Ricci dark energy in Chern-Simons modified gravity
In this work, we have considered the Ricci dark energy model, where the
energy density of the universe is proportional to the Ricci scalar curvature,
in the dynamic Chern-Simons modified gravity. We show that in this context the
evolution of the scale factor is similar to that displayed by the modified
Chaplygin gas.Comment: 7 pages; to appear in EPJ
Modelling Intermediate Age and Old Stellar Populations in the Infrared
We have investigated the spectro-photometric properties of the Asymptotic
Giant Branch (AGB) stars and their contribution to the integrated infrared
emission in simple stellar populations (SSP). Adopting analytical relations
describing the evolution of these stars in the HR diagram and empirical
relations for the mass-loss rate and the wind terminal velocity, we were able
to model the effects of the dusty envelope around these stars, with a minimal
number of parameters. We computed isochrones at different age and initial metal
content. We compare our models with existing infrared colors of M giants and
Mira stars and with IRAS PSC data. Contrary to previous models, in the new
isochrones the mass-loss rate, which establishes the duration of the AGB phase,
also determines the spectral properties of the stars. The contribution of these
stars to the integrated light of the population is thus obtained in a
consistent way. We find that the emission in the mid infrared is about one
order of magnitude larger when dust is taken into account in an intermediate
age population, irrespective of the particular mixture adopted. The dependence
of the integrated colors on the metallicity and age is discussed, with
particular emphasis on the problem of age-metallicity degeneracy. We show that,
contrary to the case of optical or near infrared colors, the adoption of a
suitable pass-band in the mid infrared allows a fair separation of the two
effects. We suggest intermediate redshift elliptical galaxies as possible
targets of this method of solving the age-metallicity dilemma. The new SSP
models constitute a first step in a more extended study aimed at modelling the
spectral properties of the galaxies from the ultraviolet to the far infrared.Comment: 16 pages, 10 figures, to appear in A&
Labyrinthine pathways towards supercycle attractors in unimodal maps
We uncover previously unknown properties of the family of periodic
superstable cycles in unimodal maps characterized each by a Lyapunov exponent
that diverges to minus infinity. Amongst the main novel properties are the
following: i) The basins of attraction for the phases of the cycles develop
fractal boundaries of increasing complexity as the period-doubling structure
advances towards the transition to chaos. ii) The fractal boundaries, formed by
the preimages of the repellor, display hierarchical structures organized
according to exponential clusterings that manifest in the dynamics as
sensitivity to the final state and transient chaos. iii) There is a functional
composition renormalization group (RG) fixed-point map associated to the family
of supercycles. iv) This map is given in closed form by the same kind of
-exponential function found for both the pitchfork and tangent bifurcation
attractors. v) There is a final stage ultra-fast dynamics towards the attractor
with a sensitivity to initial conditions that decreases as an exponential of an
exponential of time.Comment: 8 pages, 13 figure
Communicating via ignorance: Increasing communication capacity via superposition of order
Classically, no information can be transmitted through a depolarising, that
is a completely noisy, channel. We show that by combining a depolarising
channel with another channel in an indefinite causal order---that is, when
there is superposition of the order that these two channels were applied---it
becomes possible to transmit significant information. We consider two limiting
cases. When both channels are fully-depolarising, the ideal limit is
communication of 0.049 bits; experimentally we achieve
bits. When one channel is fully-depolarising,
and the other is a known unitary, the ideal limit is communication of 1 bit. We
experimentally achieve 0.640.02 bits. Our results offer intriguing
possibilities for future communication strategies beyond conventional quantum
Shannon theory
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