28 research outputs found
A Bound on the Superpotential
We prove a general bound on the superpotential in theories with broken
supersymmetry and broken R-symmetry, 2|W|< f_a F, where f_a and F are the
R-axion and Goldstino decay constants, respectively. The bound holds for weakly
coupled as well as strongly coupled theories, thereby providing an exact result
in theories with broken supersymmetry. We briefly discuss several possible
applications.Comment: 20 page
On single and double soft behaviors in NLSM
In this paper, we study the single and double soft behaviors of tree level
off-shell currents and on-shell amplitudes in nonlinear sigma model(NLSM). We
first propose and prove the leading soft behavior of the tree level currents
with a single soft particle. In the on-shell limit, this single soft emission
becomes the Adler's zero. Then we establish the leading and sub-leading soft
behaviors of tree level currents with two adjacent soft particles. With a
careful analysis of the on-shell limit, we obtain the double soft behaviors of
on-shell amplitudes where the two soft particles are adjacent to each other. By
applying Kleiss-Kuijf (KK) relation, we further obtain the leading and
sub-leading behaviors of amplitudes with two nonadjacent soft particles.Comment: 41 pages, 6 tables, 9 figures, minor revised, more content about
nonadjacent double soft limit, update the reference
Probing scalar effective field theories with the soft limits of scattering amplitudes
We investigate the soft behaviour of scalar effective field theories (EFTs) when there is a number of distinct derivative power counting parameters, ρ1 < ρ2 < . . . < ρQ. We clarify the notion of an enhanced soft limit and use these to extend the scope of onshell recursion techniques for scalar EFTs. As an example, we perform a detailed study of theories with two power counting parameters, ρ1 = 1 and ρ2 = 2, that include the shift symmetric generalised galileons. We demonstrate that the minimally enhanced soft limit uniquely picks out the Dirac-Born-Infeld (DBI) symmetry, including DBI galileons. For the exceptional soft limit we uniquely pick out the special galileon within the class of theories under investigation. We study the DBI galileon amplitudes more closely, verifying the validity of the recursion techniques in generating the six point amplitude, and explicitly demonstrating the invariance of all amplitudes under DBI galileon duality