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This is the written version of an invited talk delivered at the workshop ``Quantum gravity in the Southern Cone'' held in San Carlos de Bariloche, Argentina, January 7-10, 1998. After giving a brief introduction to the concept of branes and their role in string theory, this talk describes a method for formulating the dynamics of branes, especially...
Citations
The IceCube Neutrino Observatory is a km³ detector which recently
completed construction at the geographic South Pole. Here we present
four searches for flaring point-sources sources of neutrinos using
IceCube data using maximum-likelihood techniques. For the first time, a
search is performed over the entire parameter space of energy, direction
and time with sensitivity to neutrino flares lasting between 20 mus and
a year duration from astrophysical sources. This work is also an
important step for the IceCube experiment in utilizing a multi-messenger
approach, driving IceCube neutrino analysis with information from photon
observatories. The use of time information is useful since integrated
searches over time are less sensitive to flares as they are affected by
a larger background of atmospheric neutrinos and moons that can be
reduced by the use of additional timing information. Flaring sources
considered here, such as active galactic nuclei and gamma-ray bursts,
are promising candidate neutrino emitters. One search is "untriggered"
in the sense that it looks for any possible flare in the entire sky. The
other two searches are triggered by multi-wavelength information on
flares. One triggered search uses lightcurves from Fermi-LAT which
provides continuous monitoring. A second triggered search uses
information where the flux states have been measured only for short
periods of time near the flares. A search for periodic emission of
neutrinos is also performed on binary systems in the galaxy which are
thought to be sources of particle acceleration. The searches use data
taken by 40 strings of IceCube between Apr 5, 2008 and May 20, 2009 and
by 59 strings of IceCube between May 20, 2009 and May 31, 2010. The
results from all searches are compatible with a fluctuation of the
background.
It is proved that a basic superembedding equation for the 2-dimensional worldsheet superspace Σ(2|8+8) embedded into D=10 type IIB superspace provides a universal, S-duality invariant description of a fundamental superstring and super-D1-brane. We work out generalized action principle, obtain superfield equations of motion for both these objects and find how the S-duality transformations relate the superfield equations of superstring and super-D1-brane.The superembedding of 6-dimensional worldsheet superspace Σ(6|16) into the D=10 type IIB superspace will probably provide a similar universal description for the set of type IIB super-NS5-brane, super-D5-brane and a Kaluza–Klein monopole (super-KK5-brane).
This thesis deals with the two duality symmetries of N=2 D=10 supergravity
theories that are descendant from the full superstring theory: fermionic
T-duality and U-duality. The fermionic T-duality transformation is applied to
the D-brane and pp-wave solutions of type IIB supergravity. New supersymmetric
solutions of complexified supergravity are generated. We show that the pp-wave
yields a purely imaginary background after two dualities, undergoes a geometric
transformation after four dualities, and is self-dual after eight dualities.
Next we apply six bosonic and six fermionic T-dualities to the AdS_4 x CP^3
background of type IIA supergravity, which is relevant to the current research
in the amplitude physics. This helps to elucidate the potential obstacles in
establishing the self-duality, and quite independently from that shows us that
fermionic T-dualities may be degenerate under some circumstances. Finally, we
make a step towards constructing a manifestly U-duality covariant action for
D=10 supergravities by deriving the generalized metric for a D1-brane. This is
a single structure that treats brane wrapping coordinates on the same footing
as spacetime coordinates. It turns out that the generalized metric of a
D-string results from that of the fundamental string if one replaces the
spacetime metric with the open string metric. We also find an antisymmetric
contribution to the generalized metric that can be interpreted as a
noncommutativity parameter.
