1,295 research outputs found
Multi-soft theorems in Gauge Theory from MHV Diagrams
In this work we employ the MHV technique to show that scattering amplitudes
with any number of consecutive soft particles behave universally in the
multi-soft limit in which all particles go soft simultaneously. After
identifying the diagrams which give the leading contribution we give the
general rules for writing down compact expressions for the multi-soft factor of
m gluons, k of which have negative helicity. We explicitly consider the cases
where k equals 1 and 2. In N =4 SYM, the multi-soft factors of 2 scalars or 2
fermions forming a singlet of SU(4) R-symmetry, and m-2 positive helicity
gluons are derived. The special case of the double-soft limit gives an
amplitude whose leading divergence is 1/\delta^2 and not 1/\delta as in the
case of 2 scalars or 2 fermions that do not form a singlet under SU(4). The
construction based on the analytic supervertices allows us to obtain simple
expressions for the triple-soft limit of 1 scalar and 2 positive helicity
fermions, as well as for the quadrapole-soft limit of 4 positive helicity
fermions, in a singlet configuration.Comment: 25 pages, 7 figures,typos correcte
Holographic three-point correlators in the Schrodinger/dipole CFT correspondence
We calculate, for the first time, three-point correlation functions involving
"heavy" operators in the Schrodinger/null-dipole CFT correspondence at strong
coupling. In particular, we focus on the three-point functions of the dilaton
modes and two "heavy" operators. The heavy states are dual to the single spin
and dyonic magnon, the single spin and dyonic spike solutions or to two novel
string solutions which do not have an undeformed counterpart. Our results
provide the leading term of the correlators in the large expansion
and are in perfect agreement with the form of the correlator dictated by
non-relativistic conformal invariance. We also specify the scaling function
which can not be fixed by using conformal invariance.Comment: 26 pages, 1 figur
Integrable flows between exact CFTs
We explicitly construct families of integrable -model actions
smoothly interpolating between exact CFTs. In the ultraviolet the theory is the
direct product of two current algebras at levels and . In the
infrared and for the case of two deformation matrices the CFT involves a coset
CFT, whereas for a single matrix deformation it is given by the ultraviolet
direct product theories but at levels and . For isotropic
deformations we demonstrate integrability. In this case we also compute the
exact beta-function for the deformation parameters using gravitational methods.
This is shown to coincide with previous results obtained using perturbation
theory and non-perturbative symmetries.Comment: 1+27 pages, text improvements, version published in JHE
Novel all loop actions of interacting CFTs: Construction, integrability and RG flows
We construct the all loop effective action representing, for small couplings,
simultaneously self and mutually interacting current algebra CFTs realized by
WZW models. This non-trivially generalizes our previous works where such
interactions were, at the linear level, not simultaneously present. For the two
coupling case we prove integrability and calculate the coupled RG flow
equations. We also consider non-Abelian T-duality type limits. Our models
provide concrete realisations of integrable flows between exact CFTs and
exhibit several new features which we discuss in detail.Comment: 33 pages, 4 figures, typos corrected in version 2, version published
in Nucl. Phys.
The Underground Economy: An Overview and Estimates for Cyprus
The paper begins by describing three important macroeconomic approaches to the measurement of the underground economy. Estimates of the size of the underground economy in Cyprus are then discussed. The estimates are derived using a method first applied by Tanzi to data for the United States. Using annual times series data for the period 1960-1990 the size of the underground economy in Cyprus is estimated to be, approximately, between 3% and 10% of GNP.
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