12,502 research outputs found
On the Singularities of the Magnon S-matrix
We investigate the analytic structure of the magnon S-matrix in the
spin-chain description of planar SUSY Yang-Mills/ strings. Semiclassical analysis suggests that the exact S-matrix must
have a large family of poles near the real axis in momentum space. In this
article we show that these are double poles corresponding to the exchange of
pairs of BPS magnons. Their locations in the complex plane are uniquely fixed
by the known dispersion relation for the BPS particles. The locations precisely
agree with the recent conjecture for the matrix by Beisert, Hernandez,
Lopez, Eden and Staudacher (hep-th/0609044 and hep-th/0610251). These poles do
not signal the presence of new bound states. In fact, a certain non-BPS
localized classical solution, which was thought to give rise to new bound
states, can actually decay into a pair of BPS magnons.Comment: 40 pages, 14 figures; typos corrected, references adde
Winding Strings in AdS_3
Correlation functions of one unit spectral flowed states in string theory on
AdS_3 are considered. We present the modified Knizhnik-Zamolodchikov and null
vector equations to be satisfied by amplitudes containing states in winding
sector one and study their solution corresponding to the four point function
including one w=1 field. We compute the three point function involving two one
unit spectral flowed operators and find expressions for amplitudes of three w=1
states satisfying certain particular relations among the spins of the fields.
Several consistency checks are performed.Comment: 35 pages. v2. Important additions: one more author, complete results
for the 3-point function with two w=1 states and new section with computation
of 4-point function with one w=1 state. Acknowledgments and references
modifie
Continuum Superpartners
In an exact conformal theory there is no particle. The excitations have
continuum spectra and are called "unparticles" by Georgi. We consider
supersymmetric extensions of the Standard Model with approximate conformal
sectors. The conformal symmetry is softly broken in the infrared which
generates a gap. However, the spectrum can still have a continuum above the gap
if there is no confinement. Using the AdS/CFT correspondence this can be
achieved with a soft wall in the warped extra dimension. When supersymmetry is
broken the superpartners of the Standard Model particles may simply be a
continuum above gap. The collider signals can be quite different from the
standard supersymmetric scenarios and the experimental searches for the
continuum superpartners can be very challenging.Comment: 15 pages, 5 figures, talk at SCGT09 Workshop, Nagoya, Japan, 8-11
Dec, 200
- …