360 research outputs found
Theoretical uncertainties in extracting cosmic-ray diffusion parameters: the boron-to-carbon ratio
PAMELA and, more recently, AMS-02, are ushering us into a new era of greatly
reduced statistical uncertainties in experimental measurements of cosmic-ray
fluxes. In particular, new determinations of traditional diagnostic tools such
as the boron-to-carbon ratio (B/C) are expected to significantly reduce errors
on cosmic-ray diffusion parameters, with important implications for
astroparticle physics, ranging from inferring primary source spectra to
indirect dark matter searches. It is timely to stress, however, that the
conclusions obtained crucially depend on the framework in which the data are
interpreted as well as from some nuclear input parameters. We aim at assessing
the theoretical uncertainties affecting the outcome, with models as simple as
possible while still retaining the key dependencies. We compare different
semi-analytical, two-zone model descriptions of cosmic-ray transport in the
Galaxy. We test for the effect of a primary source contamination in the boron
flux by parametrically altering its flux, as well as for nuclear cross section
uncertainties. Our study on preliminary results from AMS-02 suggests that,
differently for instance from the leptonic case, realistic modelling of the
geometry of the Galaxy and of the source distribution are of minor importance
to correctly reproduce B/C data at high energies and thus, to a large extent,
for the extraction of diffusion parameters. The Ansatz on the lack of primary
injection of boron represents the most serious bias, and requires
multi-messenger studies to be addressed. If this uncertainty could be lifted,
nuclear uncertainties would still represent a serious concern, which degrade
the systematic error on the inferred parameters to the 20% level, or three
times the estimated experimental sensitivity. In order to reduce this, a new
nuclear cross section measurement campaign is probably required.Comment: 14 pages, 11 figures, 4 tables, published in A&
Recommended from our members
Topological AdS/CFT and the Ω deformation
In this note, we define a holographic dual to four-dimensional superconformal
field theories formulated on arbitrary Riemannian manifolds equipped with a
Killing vector. Moreover, assuming smoothness of the bulk solution, we study
the variation of the holographically renormalized supergravity action in the
class of metrics on the boundary four-manifold with a prescribed isometry
Supersymmetric gauge theories on five-manifolds
We construct rigid supersymmetric gauge theories on Riemannian
five-manifolds. We follow a holographic approach, realizing the manifold as the
conformal boundary of a six-dimensional bulk supergravity solution. This leads
to a systematic classification of five-dimensional supersymmetric backgrounds
with gravity duals. We show that the background metric is furnished with a
conformal Killing vector, which generates a transversely holomorphic foliation
with a transverse Hermitian structure. Moreover, we prove that any such metric
defines a supersymmetric background. Finally, we construct supersymmetric
Lagrangians for gauge theories coupled to arbitrary matter on such backgrounds.Comment: 35 pages: v2: minor corrections and references added. Published
versio
Magnetic charge and black hole supersymmetric quantum statistical relation
We study the thermodynamics in the BPS limit of AdS black holes realizing the
topological twist. We use a limiting procedure that allows us to reach the
extremal point along a trajectory in the space of supersymmetric Euclidean
solutions. We show that on this space we can write a quantum statistical
relation, which is well-defined in the BPS limit and relies on imposing a
suitable constraint among the chemical potentials, due to supersymmetry and
regularity. We stress the importance of this in relating the thermal partition
function of the dual field theory to the topologically twisted index.Comment: 18 pages; v2: added comments on renormalization and relation with
literatur
Recommended from our members
Localization of the action in AdS/CFT
We derive a simple formula for the action of any supersymmetric solution to
minimal gauged supergravity in the AdS/CFT correspondence. Such
solutions are equipped with a supersymmetric Killing vector, and we show that
the holographically renormalized action may be expressed entirely in terms of
the weights of this vector field at its fixed points, together with certain
topological data. In this sense, the classical gravitational partition function
localizes in the bulk. We illustrate our general formula with a number of
explicit examples, in which exact dual field theory computations are also
available, which include supersymmetric Taub-NUT and Taub-bolt type spacetimes,
as well as black hole solutions. Our simple topological formula also allows us
to write down the action of any solution, provided it exists
AMS-02 antiprotons, at last! Secondary astrophysical component and immediate implications for Dark Matter
Using the updated proton and helium fluxes just released by the AMS-02
experiment we reevaluate the secondary astrophysical antiproton to proton ratio
and its uncertainties, and compare it with the ratio preliminarly reported by
AMS-02. We find no unambiguous evidence for a significant excess with respect
to expectations. Yet, some preference for a flatter energy dependence of the
diffusion coefficient starts to emerge. Also, we provide a first assessment of
the room left for exotic components such as Galactic Dark Matter annihilation
or decay, deriving new stringent constraints.Comment: 12 pages, 5 figures; Comments and clarifications added (including an
appendix), matches version published on JCA
Gravitational free energy in topological AdS/CFT
We define and study a holographic dual to the topological twist of
gauge theories on Riemannian three-manifolds. The gravity duals
are solutions to four-dimensional gauged supergravity, where
the three-manifold arises as a conformal boundary. Following our previous work,
we show that the renormalized gravitational free energy of such solutions is
independent of the boundary three-metric, as required for a topological theory.
We then go further, analyzing the geometry of supersymmetric bulk solutions.
Remarkably, we are able to show that the gravitational free energy of any
smooth four-manifold filling of any three-manifold is always zero. Aided by
this analysis, we prove a similar result for topological AdS/CFT. We
comment on the implications of these results for the large limits of
topologically twisted gauge theories in three and four dimensions, including
the ABJM theory and super-Yang-Mills, respectively.Comment: 46 pages; v2: corrected typos, updated reference
- …