Publications de Sebastian Zell

Scale invariant Einstein-Cartan gravity and flat space conformal symmetry

Mikhail Chapochnikov, Georgios Karananas, Sebastian Zell

We find the conditions under which scale-invariant Einstein-Cartan gravity with scalar matter fields leads to an approximate conformal invariance of the flat space particle theory up to energies of the order of the Planck mass. In the minimal setup, these ...

Springer Nature2023

TimeEvolver: A program for time evolution with improved error bound

Sebastian Zell

We present TimeEvolver, a program for computing time evolution in a generic quantum system. It relies on well-known Krylov subspace techniques to tackle the problem of multiplying the exponential of a large sparse matrix iH, where His the Hamiltonian, with ...

ELSEVIER2022

Field redefinitions, perturbative unitarity and Higgs inflation

Mikhail Chapochnikov, Sebastian Zell

For inflation driven by the Higgs field coupled non-minimally to gravity, we study the cutoff energy scale above which perturbation theory breaks down. Employing the metric formulation, we first give an overview of known results and then provide a new way ...

Springer Nature2022

Coupling metric-affine gravity to a Higgs-like scalar field

Sebastian Zell

General relativity (GR) exists in different formulations. They are equivalent in pure gravity but generically lead to distinct predictions once matter is included. After a brief overview of various versions of GR, we focus on metric-affine gravity, which a ...

American Physical Society2022

Scale and Weyl invariance in Einstein-Cartan gravity

Mikhail Chapochnikov, Sebastian Zell

We show how Einstein-Cartan gravity can accommodate both global scale and local scale (Weyl) invariance. To this end, we construct a wide class of models with nonpropagating torsion and a nonminimally coupled scalar field. In phenomenological applications ...

American Physical Society2021

Einstein-Cartan Portal to Dark Matter

Mikhail Chapochnikov, Andrey Shkerin, Inar Timiryasov, Sebastian Zell

It is well known since the works of Utiyama and Kibble that the gravitational force can be obtained by gauging the Poincare group, which puts gravity on the same footing as the standard model fields. The resulting theory-Einstein-Cartan gravity-inevitably ...

AMER PHYSICAL SOC2021

Einstein-Cartan gravity, matter, and scale-invariant generalization (vol 10, 177, 2020)

Mikhail Chapochnikov, Andrey Shkerin, Inar Timiryasov, Sebastian Zell

Springer Nature2021

Standard model meets gravity: Electroweak symmetry breaking and inflation

Mikhail Chapochnikov, Andrey Shkerin, Sebastian Zell

We propose a model for combining the Standard Model (SM) with gravity. It relies on a nonminimal coupling of the Higgs field to the Ricci scalar and on the Palatini formulation of gravity. Without introducing any new degrees of freedom in addition to those ...

American Physical Society2021

Higgs inflation in Einstein-Cartan gravity

Mikhail Chapochnikov, Andrey Shkerin, Inar Timiryasov, Sebastian Zell

We study inflation driven by the Higgs field in the Einstein-Cartan formulation of gravity. In this theory, the presence of the Holst and Nieh-Yan terms with the Higgs field non-minimally coupled to them leads to three additional coupling constants. For a ...

IOP PUBLISHING LTD2021

Higgs inflation in Einstein-Cartan gravity (vol 02, 008, 2021)

Mikhail Chapochnikov, Andrey Shkerin, Inar Timiryasov, Sebastian Zell

IOP Publishing Ltd2021

Matter matters in Einstein-Cartan gravity

Mikhail Chapochnikov, Georgios Karananas, Andrey Shkerin, Sebastian Zell

We study scalar, fermionic and gauge fields coupled nonminimally to gravity in the Einstein-Cartan formulation. We construct a wide class of models with nondynamical torsion whose gravitational spectra comprise only themassless graviton. Eliminating nonpro ...

American Physical Society2021

Einstein-Cartan gravity, matter, and scale-invariant generalization

Mikhail Chapochnikov, Andrey Shkerin, Inar Timiryasov, Sebastian Zell

We study gravity coupled to scalar and fermion fields in the Einstein-Cartan framework. We discuss the most general form of the action that contains terms of mass dimension not bigger than four, leaving out only contributions quadratic in curvature. By res ...

Springer Nature2020

Quantum effects in Palatini Higgs inflation

Mikhail Chapochnikov, Andrey Shkerin, Sebastian Zell

We study quantum effects in Higgs inflation in the Palatini formulation of gravity, in which the metric and connection are treated as independent variables. We exploit the fact that the cutoff, above which perturbation theory breaks down, is higher than th ...

IOP PUBLISHING LTD2020

Black hole metamorphosis and stabilization by memory burden

Sebastian Zell

Systems of enhanced memory capacity are subjected to a universal effect of memory burden, which suppresses their decay. In this paper, we study a prototype model to show that memory burden can be overcome by rewriting stored quantum information from one se ...

American Physical Society2020