106 citations · 801 across the 31 of their papers we have counts for
32 papers
Before the Bang: Wormholes at the Dawn of the Universe
Panos Betzios, Paul Ghiringhelli, Ioannis D. Gialamas +1
This essay discusses recent progress on Euclidean wormholes as candidate contributions to the Universe's initial quantum state. The comparison with the Hartle-Hawking no-boundary p…
Quasi-pole quintessential inflation in metric-affine gravity
Konstantinos Dimopoulos, Christian Dioguardi, Ioannis D. Gialamas +1
We study quintessential inflation in the framework of metric-affine gravity. It is well known that non-minimal couplings with the Holst invariant can generate a quasi-pole inflatio…
A Menagerie of Wormholes and Cosmologies in the Gravitational Path Integral
Panos Betzios, Paul Ghiringhelli, Ioannis D. Gialamas +1
We analyse a variety of Euclidean saddles in the gravitational path integral, with asymptotic AdS boundary conditions, in a class of Einstein-Scalar-Maxwell models. These include s…
Reheating in geometric Weyl-invariant Einstein-Cartan gravity
Ioannis D. Gialamas
We study Weyl-invariant purely gravitational theories formulated within the Einstein-Cartan framework. In the Einstein-frame description, these models are dynamically equivalent to…
Toward a gravitational network: Bridging metric-affine gravity and no-scale supergravity
Ioannis D. Gialamas, Theodoros Katsoulas, Kyriakos Tamvakis
We consider a class of models in the framework of metric-affine gravity and establish their correspondence to the bosonic sector of a class of no-scale supergravity models. The exc…
Keeping the relation between the Starobinsky model and no-scale supergravity ACTive
Ioannis D. Gialamas, Theodoros Katsoulas, Kyriakos Tamvakis
We introduce a modification of the Starobinsky model in the form of an additional cubic Ricci scalar curvature term , scaled by a dimensionless parameter , with the r…
Has ACT measured radiative corrections to the tree-level Higgs-like inflation?
Ioannis D. Gialamas, Alexandros Karam, Antonio Racioppi +1
Starobinsky inflation and nonminimally coupled (NMC) Higgs inflation have been among the most favored models of the early Universe, as their predictions for the scalar spectral ind…
The Linear Collider Facility (LCF) at CERN
H. Abramowicz, E. Adli, F. Alharthi +406
In this paper we outline a proposal for a Linear Collider Facility as the next flagship project for CERN. It offers the opportunity for a timely, cost-effective and staged construc…
A Linear Collider Vision for the Future of Particle Physics
H. Abramowicz, E. Adli, F. Alharthi +446
In this paper we review the physics opportunities at linear colliders with a special focus on high centre-of-mass energies and beam polarisation, take a fresh look at the…
Dynamically induced spin-2 mass in a Weyl-invariant framework
Ioannis D. Gialamas, Kyriakos Tamvakis
We combine the ghost-free bimetric theory of gravity with the concept of local Weyl invariance, realized in the framework of Einstein-Cartan gravity. The gravitational sector, char…
Symmetry-breaking inflation in non-minimal metric-affine gravity
Ioannis D. Gialamas, Antonio Racioppi
We study symmetry-breaking inflation within the framework of metric-affine gravity. By introducing a non-minimal coupling, , between the Holst invariant and the…
Magnetic Anti-de Sitter Wormholes as seeds for Higgs Inflation
Panos Betzios, Ioannis D. Gialamas, Olga Papadoulaki
We show how certain types of magnetic asymptotically Anti-de Sitter Euclidean wormholes can catalyze the onset of inflation. These wormholes can be embedded as saddle point solutio…
Cosmic inflation in metric-affine gravity
Ioannis D. Gialamas, Kyriakos Tamvakis
In the context of metric-affine gravity theories, where the metric and connection are independent, we examine actions involving quadratic terms in the Ricci scalar curvature and th…
Inflation in Weyl-invariant Einstein-Cartan gravity
Ioannis D. Gialamas, Kyriakos Tamvakis
We consider Weyl-invariant quadratic Einstein-Cartan gravity coupled to a scalar field and study the inflationary behaviour of the coupled system of the scalar field and the pseudo…
Gravitino Thermal Production, Dark Matter, and Reheating of the Universe
Helmut Eberl, Ioannis D. Gialamas, Vassilis C. Spanos
We present a full one-loop calculation of the gravitino thermal production rate, beyond the so-called hard thermal loop approximation, using the corresponding thermal spectral func…
Interpreting DESI 2024 BAO: late-time dynamical dark energy or a local effect?
Ioannis D. Gialamas, Gert Hütsi, Kristjan Kannike +4
We perform fits to DESI, CMB and supernova data to understand the physical origin of the DESI hint for dynamical dark energy. We find that the linear parametrization of the equatio…
Generalized uncertainty principle and neutrino phenomenology
Ioannis D. Gialamas, Timo J. Kärkkäinen, Luca Marzola
Generalized uncertainty principles are effective changes to the Heisenberg uncertainty principle that emerge in several quantum gravity models. In the present letter, we study the…
Inflation and reheating in quadratic metric-affine gravity with derivative couplings
Ioannis D. Gialamas, Theodoros Katsoulas, Kyriakos Tamvakis
Within the framework of metric-affine theories of gravity, where both the metric and connection are treated as independent variables, we consider actions quadratic in the Ricci sca…
On the absence of ghosts in quadratic bigravity
Ioannis D. Gialamas, Kyriakos Tamvakis
An extension of the bimetric theory of gravity is considered that includes quadratic Ricci curvature terms associated with each metric. The issue of the Boulware-Deser ghost is ana…
Bimetric Starobinsky model
Ioannis D. Gialamas, Kyriakos Tamvakis
The bimetric theory of gravity is an extension of general relativity that describes a massive spin- particle in addition to the standard massless graviton. The theory is based o…
Bimetric-Affine Quadratic Gravity
Ioannis D. Gialamas, Kyriakos Tamvakis
Bimetric gravity, is a theory of gravity that posits the existence of two interacting and dynamical metric tensors. The spectrum of bimetric gravity consists of a massless and a ma…
Electroweak vacuum decay in metric-affine gravity
Ioannis D. Gialamas, Hardi Veermäe
We investigate the stability of the electroweak vacuum in metric-affine gravity in which the Standard Model Higgs boson can be non-minimally coupled to both the Ricci scalar and th…
Implications of Palatini gravity for inflation and beyond
Ioannis D. Gialamas, Alexandros Karam, Thomas D. Pappas +1
We present an introduction to cosmic inflation in the framework of Palatini gravity, which provides an intriguing alternative to the conventional metric formulation of gravity. In…
Gravitational corrections to electroweak vacuum decay: metric vs. Palatini
Ioannis D. Gialamas, Alexandros Karam, Thomas D. Pappas
We consider the standard Einstein-Hilbert-Higgs action where the Higgs field couples nonminimally with gravity via the term , and investigate the stability of the…