3,769 research outputs found

### Somewhere over the... what?

In order to defend his controversial claim that observation is unaided perception, Bas van Fraassen, the originator of constructive empiricism, suggested that, for all we know, the images produced by a microscope could be in a situation analogous to that of the rainbows, which are âimages of nothingâ. He added that reflections in the water, rainbows, and the like are âpublic hallucinationsâ, but it is not clear whether this constitutes an ontological category apart or an empty set. In this paper an argument will be put forward to the effect that rainbows can be thought of as events, that is, as part of a subcategory of entities that van Fraassen has always considered legitimate phenomena. I argue that rainbows are actually not images in the relevant (representational) sense and that there is no need to ontologically inflate the category of entities in order to account for them, which would run counter to the empiricist principle of parsimony

### SUSY radiative corrections on mu-tau neutrino refraction including possible R-parity breaking interactions

In this paper we investigate the one-loop radiative corrections to the
neutrino indices of refraction from supersymmetric models. We consider the
Next-to Minimal Supersymmetric extension of the Standard Model (NMSSM) which
happens to be a better supersymmetric candidate than the MSSM for both
theoretical and experimental reasons. We scan the relevant SUSY parameters and
identify regions in the parameter space which yield interesting values for
V_{mu tau}. If R-parity is broken there are significant differences between
MSSM and NMSSM contributions contrary to the R-parity conserved case. Finally,
for a non-zero CP-violating phase, we show analytically that the presence of
V_{mu tau} will explicitly imply CP-violation effects on the supernova electron
(anti-) neutrino fluxes.Comment: 23 pages, 15 figures; v2: typos and 5 figures correcte

### BPS Solutions in AdS/CFT

We study a class of exact supersymmetric solutions of type IIB Supergravity.
They have an SO(4) x SU(2) x U(1) isometry and preserve generically 4 of the 32
supersymmetries of the theory. Asymptotically AdS_5 x S^5 solutions in this
class are dual to 1/8 BPS chiral operators which preserve the same symmetries
in the N=4 SYM theory. We analyse the solutions to these equations in a large
radius asymptotic expansion: they carry charges with respect to two U(1) KK
gauge fields and their mass saturates the expected BPS bound. We also show how
the same formalism is suitable for the description of the AdS_5 x Y^{p,q}
geometries and a class of their excitations.Comment: 5 pages, Latex, uses w-art class (included). To appear in the
Proceedings of the RTN workshop "ForcesUniverse", Naples, October 9-13, 200

### Possible CP-Violation effects in core-collapse Supernovae

We study CP-violation effects when neutrinos are present in dense matter,
such as outside the proto-neutron star formed in a core-collapse supernova.
Using general arguments based on the Standard Model, we confirm that there are
no CP-violating effects at the tree level on the electron neutrino and
anti-neutrino fluxes in a core-collapse supernova. On the other hand
significant effects can be obtained for muon and tau neutrinos even at the tree
level. We show that CP violating effects can be present in the supernova
electron (anti)neutrino fluxes as well, if muon and tau neutrinos have
different fluxes at the neutrinosphere. Such differences could arise due to
physics beyond the Standard Model, such as the presence of flavor-changing
interactions.Comment: 11 pages, 18 figure

### 3D gauged supergravity from SU(2) reduction of $N=1$ 6D supergravity

We obtain Yang-Mills $SU(2)\times G$ gauged supergravity in three dimensions
from $SU(2)$ group manifold reduction of (1,0) six dimensional supergravity
coupled to an anti-symmetric tensor multiplet and gauge vector multiplets in
the adjoint of $G$. The reduced theory is consistently truncated to $N=4$ 3D
supergravity coupled to $4(1+\textrm{dim}\, G)$ bosonic and $4(1+\textrm{dim}\,
G)$ fermionic propagating degrees of freedom. This is in contrast to the
reduction in which there are also massive vector fields. The scalar manifold is
$\mathbf{R}\times \frac{SO(3,\, \textrm{dim}\, G)}{SO(3)\times
SO(\textrm{dim}\, G)}$, and there is a $SU(2)\times G$ gauge group. We then
construct $N=4$ Chern-Simons $(SO(3)\ltimes \mathbf{R}^3)\times (G\ltimes
\mathbf{R}^{\textrm{dim}G})$ three dimensional gauged supergravity with scalar
manifold $\frac{SO(4,\,1+\textrm{dim}G)}{SO(4)\times SO(1+\textrm{dim}G)}$ and
explicitly show that this theory is on-shell equivalent to the Yang-Mills
$SO(3)\times G$ gauged supergravity theory obtained from the $SU(2)$ reduction,
after integrating out the scalars and gauge fields corresponding to the
translational symmetries $\mathbf{R}^3\times \mathbf{R}^{\textrm{dim}\, G}$.Comment: 24 pages, no figures, references added and typos correcte

### On Subleading Contributions to the AdS/CFT Trace Anomaly

In the context of the AdS/CFT correspondence, we perform a direct computation
in AdS_5 supergravity of the trace anomaly of a d=4, N=2 SCFT. We find
agreement with the field theory result up to next to leading order in the 1/N
expansion. In particular, the order N gravitational contribution to the anomaly
is obtained from a Riemann tensor squared term in the 7-brane effective action
deduced from heterotic - type I duality. We also discuss, in the AdS/CFT
context, the order N corrections to the trace anomaly in d=4, N=4 SCFTs
involving SO or Sp gauge groups.Comment: 25 pages, LaTeX, v2: references adde

### Shockwaves in Supernovae: New Implications on the Diffuse Supernova Neutrino Background

We investigate shock wave effects upon the diffuse supernova neutrino
background using dynamic profiles taken from hydrodynamical simulations and
calculating the neutrino evolution in three flavors with the S-matrix
formalism. We show that the shock wave impact is significant and introduces
modifications of the relic fluxes by about $20 \%$ and of the associated event
rates at the level of $10-20 \%$. Such an effect is important since it is of
the same order as the rate variation introduced when different oscillation
scenarios (i.e. hierarchy or $\theta_{13}$) are considered. In addition, due to
the shock wave, the rates become less sensitive to collective effects, in the
inverted hierarchy and when $\sin^2 2 \theta_{13}$ is between the Chooz limit
and $10^{-5}$. We propose a simplified model to account for shock wave effects
in future predictions.Comment: 8 pages, 9 figure

### The K-process on a tree as a scaling limit of the GREM-like trap model

We introduce trap models on a finite volume $k$-level tree as a class of
Markov jump processes with state space the leaves of that tree. They serve to
describe the GREM-like trap model of Sasaki and Nemoto. Under suitable
conditions on the parameters of the trap model, we establish its infinite
volume limit, given by what we call a $K$-process in an infinite $k$-level
tree. From this we deduce that the $K$-process also is the scaling limit of the
GREM-like trap model on extreme time scales under a fine tuning assumption on
the volumes.Comment: Published in at http://dx.doi.org/10.1214/13-AAP937 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org

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