10,608 research outputs found
Flat Symplectic Bundles of N-Extended Supergravities, Central Charges and Black-Hole Entropy
In these lectures we give a geometrical formulation of N-extended
supergravities which generalizes N=2 special geometry of N=2 theories. In all
these theories duality symmetries are related to the notion of "flat symplectic
bundles" and central charges may be defined as "sections" over these bundles.
Attractor points giving rise to "fixed scalars" of the horizon geometry and
Bekenstein-Hawking entropy formula for extremal black-holes are discussed in
some details.Comment: Based on lectures given by S. Ferrara at the 5th Winter School on
Mathematical Physics held at the Asia Pacific Center for Theoretical Physics,
Seul (Korea), February 199
The Role of Stellar Feedback and Dark Matter in the Evolution of Dwarf Galaxies
Supernova and multiple supernova events regulate several structural
properties of dwarf galaxies. In particular, they govern the metal enrichment
and the energy budget of the ISM; they might induce partial (blowout) or total
(blowaway) gas removal from the galaxy; the morphology of the galactic gaseous
body. Significant amounts of dark matter may play an equally important role:
the dark matter gravitational potential tends to concentrate baryons towards
the center, thus enhancing both the star formation rate and metal production.
Also, the dynamical properties of the ISM, and the occurrence of a blowout or
blowaway are shown to be determined by the dark matter content. We present
detailed analytical/numerical models describing the evolution of dwarf
Irregular galaxies including the above and other effects. The main results are:
(i) dwarfs with total masses M\simlt 5\times 10^6 M_\odot are blown away;
those with gas masses up to lose mass in an outflow; (ii)
metallicities are found to correlate tightly with dark matter content and are
consistent with a range of dark-to-visible mass ratios with
about 65% of the dwarfs in the sample having ; (iii) we
predict a lower limit to the oxygen abundance in dIs of ; (iv) outflows are not particularly important for the metallicity
evolution of dwarf galaxies and certainly less than star formation for gas
consumption; however, dwarfs with gas masses few are
shown to be the major pollutants of the IGM; (v) the ISM HI velocity dispersion
correlates with metallicity and, indepentently of dark matter, scales as
. (Abridged)Comment: 56 pages, aasms4.sty, LaTeX, 12 figures. MNRAS, submitte
Short representations of SU(2,2/N) and harmonic superspace analyticity
We consider the harmonic superspaces associated to SU(2,2/N) superconformal
algebras. For arbitrary N, we show that massless representations, other than
the chiral ones, correspond to [N/2] ``elementary'' ultrashort analytic
superfields whose first component is a scalar in the k antisymmetric irrep of
SU(N) (k=1... [N/2]) with top spin . For
N=2n we analyze UIR's obtained by tensoring the self-conjugate ultrashort
multiplet = (n/2,0) and show that N-1 different basic
products give rise to all possible UIR's with residual shortening.Comment: references adde
Maurer-Cartan Equations and Black Hole Superpotentials in N =8 Supergravity
We retrieve the non-BPS extremal black hole superpotential of N=8, d=4
supergravity by using the Maurer-Cartan equations of the symmetric space
E_7(7)/SU(8). This superpotential was recently obtained with different 3- and
4-dimensional techniques. The present derivation is independent on the
reduction to d=3.Comment: 1+22 page
(2,0) Superconformal OPEs in D=6, Selection Rules and Non-renormalization Theorems
We analyse the OPE of any two 1/2 BPS operators of (2,0) SCFT by
constructing all possible three-point functions that they can form with
another, in general long operator. Such three-point functions are uniquely
determined by superconformal symmetry. Selection rules are derived, which allow
us to infer ``non-renormalization theorems'' for an abstract superconformal
field theory. The latter is supposedly related to the strong-coupling dynamics
of coincident M5 branes, dual, in the large- limit, to the bulk
M-theory compactified on AdSS. An interpretation of extremal and
next-to-extremal correlators in terms of exchange of operators with protected
conformal dimension is given.Comment: some details correcte
Non-anticommutative chiral singlet deformation of N=(1,1) gauge theory
We study the SO(4)x SU(2) invariant Q-deformation of Euclidean N=(1,1) gauge
theories in the harmonic superspace formulation. This deformation preserves
chirality and Grassmann harmonic analyticity but breaks N=(1,1) to N=(1,0)
supersymmetry. The action of the deformed gauge theory is an integral over the
chiral superspace, and only the purely chiral part of the covariant superfield
strength contributes to it. We give the component form of the N=(1,0)
supersymmetric action for the gauge groups U(1) and U(n>1). In the U(1) and
U(2) cases, we find the explicit nonlinear field redefinition (Seiberg-Witten
map) relating the deformed N=(1,1) gauge multiplet to the undeformed one. This
map exists in the general U(n) case as well, and we use this fact to argue that
the deformed U(n) gauge theory can be nonlinearly reduced to a theory with the
gauge group SU(n).Comment: 1+25 pages; v2: corrected eqs.(2.7),(3.12),(4.31-33) and typos; v3:
corrected eqs.(3.29),(4.7),(A.5),(A.21), ref. added, published versio
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