arXiv subjects

Wanda Isnard

Publications and source records attributed to Wanda Isnard.

6 recordsLinked to original sources

arXiv2026

One loop renormalization of 5D gauge-Yukawa theories

The common lore dictates that extra dimensional theories loose predictive power at energies just above the compatification scale, due to the power-law running of bulk coupling. We show that five-dimensional gauge-Yukawa theories can be valid up to arbitrarily high scales, provided: 1) A finite number of terms are required to absorb power-law divergences; 2) All power-law running couplings flow to UV fixed points. By explicitly computing bulk and localized divergences for a gauge-Yukawa theory on $\mathcal{S}^1/\mathbb{Z}_2$, we prove the one-loop renormalization properties of Lagrangians containing only interactions that would be renormalizable in four dimensions. The existence of UV fixed points imposes further constraints on the content of the model. Our results provide a consistency check for the high-energy behavior of any 5D theory, and provide a discrimination between UV consistent models and those that can describe only a handful of Kaluza-Klein modes. Hence, we offer the first concrete step towards an all-order proof of `renormalizability' for gauge-Yukawa theories in five dimensions.

hep-th↗

arXiv2025

Composite Hybrid Inflation : Primordial Black Holes and Stochastic Gravitational Waves

We investigate the production of primordial black holes and gravitational waves in composite hybrid inflation. Starting from an effective chiral Lagrangian with a dilaton and pions, we identify inflation occurring due to the walking dynamics of the theory. A $\mathbb{Z}_2$ symmetry-breaking term in the pion sector induces a shift in the inflaton's trajectory, which leads to a tachyonic instability phase. Curvature perturbations grow exponentially, producing copious primordial black holes and a stochastic gravitational wave background. We show that the primordial black hole mass and the gravitational wave frequency are strongly restricted by the anomalous dimensions of the pion operators, with larger anomalous dimensions giving lighter primordial black holes and higher frequency gravitational waves. In both cases, the associated signatures lie within reach of future gravitational wave observatories.

hep-ph↗

arXiv2025

Are there minimal exceptional aGUTs from stable 5D orbifolds?

In analysing five dimensional orbifolds with exceptional gauge groups, we seek to find stable vacua configurations which satisfy the minimal requirements for asymptotic grand unified models. In this respect we show that no minimal asymptotic grand unified theory can be built. Our results point towards non-minimal models based on $E_6$: one featuring supersymmetry, and the other needing a modification of the Coleman-Weinberg potential to stabilise the breaking of $E_6$ to the standard model gauge group.

hep-ph↗

arXiv2024

General vacuum stability of orbifold gauge breaking and application to asymptotic grand unification

We examine the vacuum stability of gauge symmetry breaking in five dimensions, compactified on the $S_1/(\mathbb{Z}_2 \times \mathbb{Z}'_2)$ orbifold. We consider $SU(N)$, $Sp(N)$, $SO(2N)$ and $SO(2N+1)$ theories in the bulk, and provide an exhaustive classification of possible parity assignments that lead to stable orbifolds and of the corresponding symmetry breaking patterns. We use these results in the search for viable asymptotic grand unification theories (aGUT), testing the stability criteria on models based on $SU(6)$ and $SU(8)$. As a result, we identify two viable aGUTs: a unique $SU(6)$ pathway down to the Standard Model, and one $SU(8)$ model leading to an intermediate Pati-Salam partial unification.

hep-ph↗

arXiv2023

Composite Hybrid Inflation: Dilaton and Waterfall Pions

We investigate the possibility that inflation originates from a composite field theory, in terms of an effective chiral Lagrangian involving a dilaton and pions. The walking dynamics of the theory constrain the potential in a specific way, where the anomalous dimensions of operators involving pions play a crucial role. For realistic values of the anomalous dimensions, we find a successful hybrid inflation occurring via the dilaton-inflaton, with the pions acting as waterfall fields. Compositeness consistency strongly constrain the model, predicting a dilaton scale $f_\chi \sim \mathcal{O} (1)$ in unit of the Planck scale, an inflation scale $H_\text{inf} \sim 10^{10}$ GeV, and the pion scale around $10^{14}$ GeV. We further discuss possible phenomenological consequences of this theory.

hep-ph↗

arXiv2023

Hidden Supersymmetric Dark Sectors

The attractive feature of supersymmetry is predictive power, due to the large number of calculable properties and to coupling non-renormalisation. This power can be fully expressed in hidden sectors where supersymmetry may be exact, as these sectors are secluded from the visible one where instead supersymmetry must be broken. This suggests a new paradigm for supersymmetric dark sectors, where supersymmetry is exact at the dark matter scale, implying that many properties of hidden supersymmetric dark sectors can be fully computed. As a proof of concept we discuss a concrete example based on $\mathcal{N}=1$ super Yang-Mills.

hep-ph↗