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Search: authors:"Ignatios Antoniadis"

11 papers found.
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Nonlinear \( \mathcal{N}=2 \) global supersymmetry

We study the partial breaking of \( \mathcal{N}=2 \) global supersymmetry, using a novel formalism that allows for the off-shell nonlinear realization of the broken supersymmetry, extending previous results scattered in the literature. We focus on the Goldstone degrees of freedom of a massive \( \mathcal{N}=1 \) gravitino multiplet which are described by deformed \( \mathcal{N}=2 ...

Curved branes with regular support

We study spacetime singularities in a general five-dimensional braneworld with curved branes satisfying four-dimensional maximal symmetry. The bulk is supported by an analog of perfect fluid with the time replaced by the extra coordinate. We show that contrary to the existence of finite-distance singularities from the brane location in any solution with flat (Minkowski) branes, in ...

Isometries, gaugings and \( \mathcal{N} \) = 2 supergravity decoupling

We study off-shell rigid limits for the kinetic and scalar-potential terms of a single \( \mathcal{N} \) = 2 hypermultiplet. In the kinetic term, these rigid limits establish relations between four-dimensional quaternion-Kähler and hyper-Kähler target spaces with symmetry. The scalar potential is obtained by gauging the graviphoton along an isometry of the quaternion-Kähler space. ...

Sequestered gravity in gauge mediation

We present a novel mechanism of supersymmetry breaking embeddable in string theory and simultaneously sharing the main advantages of (sequestered) gravity and gauge mediation. It is driven by a Scherk–Schwarz deformation along a compact extra dimension, transverse to a brane stack supporting the supersymmetric extension of the Standard Model. This fixes the magnitude of the ...

The coupling of non-linear supersymmetry to supergravity

We study the coupling of non-linear supersymmetry to supergravity. The goldstino nilpotent superfield of global supersymmetry coupled to supergravity is described by a geometric action of the chiral curvature superfield \(\mathscr {R}\) subject to the constraint \((\mathscr {R}-\lambda )^2=0\) with an appropriate constant \(\lambda \). This constraint can be found as the decoupling ...

Ambient cosmology and spacetime singularities

We present a new approach to the issues of spacetime singularities and cosmic censorship in general relativity. This is based on the idea that standard 4-dimensional spacetime is the conformal infinity of an ambient metric for the 5-dimensional Einstein equations with fluid sources. We then find that the existence of spacetime singularities in four dimensions is constrained by ...

The effective Planck mass and the scale of inflation

Observable quantities in cosmology are dimensionless, and therefore independent of the units in which they are measured. This is true of all physical quantities associated with the primordial perturbations that source cosmic microwave background anisotropies such as their amplitude and spectral properties. However, if one were to try and infer an absolute energy scale for ...

Enveloping branes and brane-world singularities

The existence of envelopes is studied for systems of differential equations in connection with the method of asymptotic splittings which allows one to determine the singularity structure of the solutions. The result is applied to brane-worlds consisting of a 3-brane in a five-dimensional bulk, in the presence of an analog of a bulk perfect fluid parameterizing a generic class of ...

Goldstinos, supercurrents and metastable SUSY breaking in \( \mathcal{N} = 2 \) supersymmetric gauge theories

We construct an \( \mathcal{N} = 2 \) supersymmetric generalization of the \( \mathcal{N} = 1 \) supercurrent formalism of Komargodski and Seiberg (KS) and use it to show that \( \mathcal{N} = 2 \) theories with linear superconformal anomalies cannot break SUSY under certain broad assumptions. This result suggests that there are no metastable SUSY breaking vacua in a large class of ...

The hypermultiplet with Heisenberg isometry in N = 2 global and local supersymmetry

The string coupling of N = 2 supersymmetric compactifications of type II string theory on a Calabi-Yau manifold belongs to the so-called universal dilaton hyper-multiplet, that has four real scalars living on a quaternion-Kähler manifold. Requiring Heisenberg symmetry, which is a maximal subgroup of perturbative isometries, reduces the possible manifolds to a one-parameter family ...