arXiv subjects

Alexis Kassiteridis

Publications and source records attributed to Alexis Kassiteridis.

6 recordsLinked to original sources

arXiv2021

Small-scale Cosmic Signatures of Feebly Interacting Massive Particles

Feebly Interacting Massive Particles (FIMPs), if they exist, should be notoriously difficult to detect even indirectly. In order to constrain them, we derive bounds for feeble theories sourced via Standard Model fields by investigating their predicted signatures regarding small-scale structure formation. To achieve this, we obtain an analytic approximation for the phase-space distribution function for a generic dimension $\ell$ scattering operator. As a proof of concept, realizations of such theories are discussed, which provide a viable thermal evolution and are able to solidly solve the enduring small-scale structure challenges appearing in $Λ$CDM cosmology.

hep-ph↗

arXiv2021

Cosmic structure formation in a flavoured U$\left(1\right)$ dark sector at small scales

In this work we study the footprint of a secluded dark sector with a U$\left(1\right)$ gauge symmetry on the formation of cosmic structure at small scales. A single generation of dark fermions with mass in the TeV range is able to elegantly solve all small-scale issues of structure formation, while still being consistent with the cosmological history of the universe. A new interaction at the MeV scale is introduced for this purpose. As a generalization we consider multiple generations of fermions as well and show that such extensions are also cosmologically viable and allow a more flexible choice of the parameters of the theory.

hep-ph↗

arXiv2018

Small-scale structure from charged leptophilia

We consider a charged leptophilic extension of the Standard Model of particle physics as a minimal dark sector. It accomodates a WIMP paradigm at the TeV-scale that is sufficient to solve all small-scale problems of $Λ$CDM and explain the excess of highly energetic cosmic ray Standard Model electrons and positrons presented recently by the DAMPE collaboration. The predictive power of this model allows to test it in the near future.

hep-ph↗

arXiv2018

Small-scale structure from neutron dark decay

It was recently proposed that the disagreement in the experimental measurements of the lifetime of the neutron might be eradicated if the neutron decays to particles responsible for the dark matter in the Universe. In this paper we construct a proto- type self-interacting dark matter model which, apart from reproducing the correct relic abundance, resolves all small-scale problems of the $Λ$CDM paradigm. The theory is compatible with all present cosmological observations and astrophysical bounds.

hep-ph↗

arXiv2018

Cosmological singlet diagnostics of neutrinophilic dark matter

The standard model of particle physics is extended by adding a purely neutrinophilic dark sector. It is shown that theories which accommodate standard model neutrinos as dark radiation are resurrected. Sterile neutrinos bridge the visible and the dark sector and can keep their mutual interactions effective even after the epoch of big bang nucleosythesis. This prolonged contact between dark matter and standard model neutrinos solves the well-known small-scale structure problems of the cosmological standard model. The dark sector presented in this work satisfies all experimental and observational constraints from particle physics and cosmology.

hep-ph↗

arXiv2016

On massless dyadic forms and no minimal coupling theorem

We use the spinor helicity formalism in order to derive the dyadic forms for massless fields of various spins. We also give an iterated form of this approach in case higher spin theories are under study. This reduces calculations at hard and soft scattering problems in gauge theories drastically. Finally, we state and prove a theorem of gauge symmetry violation in the presence of minimal coupling with light in higher spin theories ($j>1/2$).

hep-th↗