134 research outputs found
Superspace evaluation of the two-loop effective potential for the O'Raifeartaigh model
All-order spurion-corrected superpropagators and superfield Feynman rules are
employed to systematically compute a two-loop corrected effective potential for
the O'Raifeartaigh model, that realizes spontaneous supersymmetry breaking.
Though the shifted superpropagators are rather nontrivial, superspace
techniques may be suitably extended and confirm their efficacy in computing
radiative corrections even when supersymmetry breakdown occurs.Comment: 24 pages, 2 figures, revtex4, 2 pages added, new appendix adde
Supergraph Approach in a Higher-order LDE Calculation of the Effective Potential for F-type Broken SUSY
In this work, we adopt the simplest model that spontaneously breaks
supersymmetry, namely, the minimal O'Raifeartaigh model. The effective
potential is computed in the framework of the linear delta expansion (LDE)
approach up to the order , conjugated with superspace and supergraph
techniques. The latter can be duly mastered even if supersymmetry is no longer
exact and the efficacy of the superfield approach in connection with the LDE
procedure is confirmed according to our investigation. That opens up a way for
a semi-nonperturbative superspace computation which allows us to deal with
spontaneously broken supersymmetric models and encourages us to go further and
apply this treatment to the Minimal Supersymmetric Standard Model (MSSM)
precision tests.Comment: 42 pages, 22 figures, text modified, new paragraph added in the
conclusions, revtex
Superspace approach to the renormalization of the O'Raifeartaigh model up to the second order in the LDE parameter
We adopt a superspace/supergraph formalism to pursue the investigation of the
structure of one- and two-loop divergences in the frame of the minimal
O'Raifeartaigh model that realizes the F-term spontaneous supersymmetry
breaking. The linear delta expansion(LDE) procedure is introduced and
renormalization is carried out up to the second order in the LDE expansion
parameter. In agreement with the nonrenormalization theorem for the
(chiral/antichiral) matter potential of supersymmetry,
our explicit supergraph calculations confirm that only the K\"{a}hler potential
is actually renomalized.Comment: 23 pages, 4 figures, revtex4. arXiv admin note: text overlap with
arXiv:0904.467
Linear delta expansion applied to the O'Raifeartaigh model
We reassess the method of the linear delta expansion for the calculation of
effective potentials in superspace, by adopting the improved version of the
super-Feynman rules in the framework of the O'Raifeartaigh model for
spontaneous supersymmetry breaking. The effective potential is calculated using
both the fastest apparent convergence and the principle of minimal sensitivity
criteria and the consistency and efficacy of the method are checked in deriving
the Coleman-Weinberg potential.Comment: 20 pages, 2 figures, revtex4, revised and extended, published versio
Mass dimension one fermions and their gravitational interaction
We investigate in detail the interaction between the spin- fields
endowed with mass dimension one and the graviton. We obtain an interaction
vertex that combines the characteristics of scalar-graviton and Dirac's
fermion-graviton vertices, due to the scalar-dynamic attribute and the
fermionic structure of this field. It is shown that the vertex obtained obeys
the Ward-Takahashi identity, ensuring the gauge invariance for this
interaction. In the contribution of the mass dimension one fermion to the
graviton propagator at one-loop, we found the conditions for the cancellation
of the tadpole term by a cosmological counter-term. We calculate the scattering
process for arbitrary momentum. For low energies, the result reveals that only
the scalar sector present in the vertex contributes to the gravitational
potential. Finally, we evaluate the non relativistic limit of the gravitational
interaction and obtain an attractive Newtonian potential, as required for a
dark matter candidate.Comment: 8 pages, 3 figure
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