arXiv subjects

Marek Lewicki

Publications and source records attributed to Marek Lewicki.

At least 73 records · Page 4Linked to original sources

arXiv2019

Probing the pre-BBN universe with gravitational waves from cosmic strings

Many motivated extensions of the Standard Model predict the existence of cosmic strings. Gravitational waves originating from the dynamics of the resulting cosmic string network have the ability to probe many otherwise inaccessible properties of the early universe. In this study we show how the spectrum of gravitational waves from a cosmic string network can be used to test the equation of state of the early universe prior to Big Bang Nucleosynthesis (BBN). We also demonstrate that current and planned gravitational wave detectors such as LIGO, LISA, DECIGO/BBO, and ET/CE have the potential to detect signals of a non-standard pre-BBN equation of state and evolution of the early universe (e.g., early non-standard matter domination or kination domination) or new degrees of freedom active in the early universe beyond the sensitivity of terrestrial collider experiments and cosmic microwave background measurements.

hep-ph↗

arXiv2018

A global study of the extended scalar singlet model

We present preliminary results from a global study of the extended scalar singlet model with a fermionic dark matter (DM) candidate. In addition to requiring a successful electroweak baryogenesis, we combine constraints from the DM relic density, direct detection limits from PandaX-II experiment, electroweak precision observables and Higgs searches at colliders. In agreement with previous studies, we find that the model can simultaneously explain (at least a part of) the observed DM abundance and matter-antimatter asymmetry. The viable points often lead to strong gravitational wave (GW) signals that can potentially be probed at future GW experiments.

hep-ph↗

arXiv2017

Gravitational wave signals and cosmological consequences of gravitational reheating

Reheating after inflation can proceed even if the inflaton couples to Standard Model (SM) particles only gravitationally. However, particle production during the transition between de-Sitter expansion and a decelerating Universe is rather inefficient and the necessity to recover the visible Universe leads to a non-standard cosmological evolution initially dominated by remnants of the inflaton field. We remain agnostic to the specific dynamics of the inflaton field and discuss a generic scenario in which its remnants behave as a perfect fluid with a general barotropic parameter $w$. Using CMB and BBN constraints we derive the allowed range of inflationary scales. We also show that this scenario results in a characteristic primordial Gravitational Wave (GW) spectrum which gives hope for observation in upcoming runs of LIGO as well as in other planned experiments.

astro-ph.CO↗

arXiv2017

Cosmic Archaeology with Gravitational Waves from Cosmic Strings

Cosmic strings are generic cosmological predictions of many extensions of the Standard Model of particle physics, such as a $U(1)^\prime$ symmetry breaking phase transition in the early universe or remnants of superstring theory. Unlike other topological defects, cosmic strings can reach a scaling regime that maintains a small fixed fraction of the total energy density of the universe from a very early epoch until today. If present, they will oscillate and generate gravitational waves with a frequency spectrum that imprints the dominant sources of total cosmic energy density throughout the history of the universe. We demonstrate that current and future gravitational wave detectors, such as LIGO and LISA, could be capable of measuring the frequency spectrum of gravitational waves from cosmic strings and discerning the energy composition of the universe at times well before primordial nucleosynthesis and the cosmic microwave background where standard cosmology has yet to be tested. This work establishes a benchmark case that gravitational waves may provide an unprecedented, powerful tool for probing the evolutionary history of the very early universe.

hep-ph↗

arXiv2017

Domain walls in the extensions of the Standard Model

Our main interest is the evolution of domain walls of the Higgs field in the early Universe. The aim of this paper is to understand how dynamics of Higgs domain walls could be influenced by yet unknown interactions from beyond the Standard Model. We assume that the Standard Model is valid up to certain, high, energy scale $Λ$ and use the framework of the effective field theory to describe physics below that scale. Performing numerical simulations with different values of the scale $Λ$ we are able to extend our previous analysis and determine its range of validity. We study domain walls interpolating between the physical electroweak vacuum and the vacuum appearing at very high field strengths. These domain walls could be formed from non-homogeneous configurations of the Higgs field produced by quantum fluctuations during inflation or thermal fluctuations during reheating. Our numerical simulations show that evolution of Higgs domain walls is rather insensitive to interactions beyond the Standard Model as long as masses of new particles are grater than $10^{12}\ \textrm{GeV}$. For lower values of $Λ$ the RG improved effective potential is strongly modified at field strengths crucial to the evolution of domain walls. For instance its minima become degenerate for $Λ$ around $10^{11}\ \textrm{GeV}$. We find that even in the case when the minima of the potential are nearly degenerate Higgs domain walls decayed shortly after their formation for generic initial conditions. On the other hand, in simulations with specifically chosen initial conditions Higgs domain walls can live longer and enter the scaling regime. We also determine the energy spectrum of gravitational waves produced by decaying domain walls of the Higgs field. For generic initial field configurations the amplitude of the signal is too small to be observed in present and planned detectors.

hep-ph↗

arXiv2017

Gravitational wave, collider and dark matter signals from a scalar singlet electroweak baryogenesis

We analyse a simple extension of the SM with just an additional scalar singlet coupled to the Higgs boson. We discuss the possible probes for electroweak baryogenesis in this model including collider searches, gravitational wave and direct dark matter detection signals. We show that a large portion of the model parameter space exists where the observation of gravitational waves would allow detection while the indirect collider searches would not.

hep-ph↗

arXiv2017

Towards the fate of the oscillating false vacuum

Motivated by cosmological examples we study quantum field theoretical tunnelling from an initial state where the "classical field", i.e. the vacuum expectation value of the field operator is spatially homogeneous but performing a time-dependent oscillation about a local minimum. In particular we estimate both analytically and numerically the exponential contribution to the tunnelling probability. We additionally show that after the tunnelling event, the classical field solution - the so-called "bubble" - mediating the phase transition can either grow or collapse. We present a simple analytical criterium to distinguish between the two behaviours.

hep-ph↗

arXiv2017

Non-minimally coupled gravity and vacuum stability

We investigate the properties of vacuum decay taking into account a non-minimal coupling to gravity. We extend the standard thin-wall solution to include the non-minimal coupling and verify its validity by comparison with a full numerical study. We also investigate the implications of a~large cosmological constant whose influence on the geometry boosts the tunneling rate. Our analysis shows that the influence of the non-minimal coupling differs significantly between the cases of Minkowski and deSitter backgrounds.

hep-ph↗

arXiv2016

Domain walls and gravitational waves in the Standard Model

We study domain walls which can be created in the Standard Model under the assumption that it is valid up to very high energy scales. We focus on domain walls interpolating between the physical electroweak vacuum and the global minimum appearing at very high field strengths. The creation of the network which ends up in the electroweak vacuum percolating through the Universe is not as difficult to obtain as one may expect, although it requires certain tuning of initial conditions. Our numerical simulations confirm that such domain walls would swiftly decay and thus cannot dominate the Universe. We discuss the possibility of detection of gravitational waves produced in this scenario. We have found that for the standard cosmology the energy density of these gravitational waves is too small to be observed in present and planned detectors.

astro-ph.CO↗

arXiv2016

EW baryogenesis via DM

We discuss the impact of a swifter cosmological expansion induced by modified cosmological history of the universe on scenarios realising electroweak baryogenesis. We detail the possible experimental bounds one can place on such cosmological modification and show how the detection capabilities of particle models are modified within these bounds. On the particle physics side we focus on the Standard Model supplemented by a dimension six operator which directly modifies the Higgs potential. We show that due to the cosmological modification, electroweak baryogenesis in this model can be realized, with the modification of the triple Higgs coupling below HL-LHC sensitivity.

hep-ph↗

arXiv2016

Gravitational wave and collider implications of electroweak baryogenesis aided by non-standard cosmology

We consider various models realizing baryogenesis during the electroweak phase transition (EWBG). Our focus is their possible detection in future collider experiments and possible observation of gravitational waves emitted during the phase transition. We also discuss the possibility of a non-standard cosmological history which can facilitate EWBG. We show how acceptable parameter space can be extended due to such a modification and conclude that next generation precision experiments such as the ILC will be able to confirm or falsify many models realizing EWBG. We also show that, in general, collider searches are a more powerful probe than gravitational wave searches. However, observation of a deviation from the SM without any hints of gravitational waves can point to models with modified cosmological history that generically enable EWBG with weaker phase transition and thus, smaller GW signals.

hep-ph↗

arXiv2016

Implications of extreme flatness in a general f(R) theory

We discuss a modified gravity theory defined by $f(R) = \sum_{n}^{l} α_n M^{2(1-n)} R^n$. We consider both finite and infinite number of terms in the series while requiring that the Einstein frame potential of the theory has a flat area around any of its stationary points. We show that the requirement of maximally flat stationary point leads to the existence of the saddle point (local maximum) for even (odd) $l$. In both cases for $l\to\infty$ one obtains the Starobinsky model with small, exponentially suppressed corrections. Besides the GR minimum the Einstein frame potential has an anti de Sitter vacuum. However we argue that the GR vacuum is absolutely stable and AdS cannot be reached neither via classical evolution nor via quantum tunnelling. Our results show that a Starobinsky-like model is the only possible realisation of $f(R)$ theory with an extremely flat area in the Einstein frame potential.

hep-th↗

arXiv2016

Multi-phase induced inflation in theories with non-minimal coupling to gravity

In this paper we investigate the induced inflation with two flat regions: one Starobinsky-like plateau in big field regime and one shorter plateau around the saddle point of the Einstein frame potential. This multi-phase inflationary scenario can be used to solve the problem of classical cosmology. The inflation at the saddle-point plateau is consistent with the data and can have arbitrarily low scale. The results can be useful in the context of the Higgs-Axion relaxation and in a certain limit they are equivalent to the $α$-attractors.

astro-ph.CO↗

arXiv2016

The impact of non-minimally coupled gravity on vacuum stability

We consider vacuum decay in the presence of a non-minimal coupling to gravity. We extend the usual thin-wall solution to include the non-minimal coupling. We also perform a full numerical study and discuss the validity of the new thin-wall approximation. Implications of a large cosmological constant, whose influence on the geometry boosts the tunnelling rate, are discussed. Our results show that the influence of the non-minimal coupling differs significantly between the cases of Minkowski and deSitter backgrounds. In the latter the decay probability quickly decreases when the coupling grows and in fact the vacuum can be made absolutely stable simply due to introduction of the non-minimal coupling. In the case of Minkowski background the effect is much weaker and the decay rate even increases for small values of the non-minimal coupling.

hep-ph↗

arXiv2016

Enabling Electroweak Baryogenesis through Dark Matter

We study the impact on electroweak baryogenesis from a swifter cosmological expansion induced by dark matter. We detail the experimental bounds that one can place on models that realize it, and we investigate the modifications of these bounds that result from a non-standard cosmological history. The modifications can be sizeable if the expansion rate of the Universe increases by several orders of magnitude. We illustrate the impact through the example of scalar field dark matter, which can alter the cosmological history enough to enable a strong-enough first-order phase transition in the Standard Model when it is supplemented by a dimension six operator directly modifying the Higgs boson potential. We show that due to the modified cosmological history, electroweak baryogenesis can be realized, while keeping deviations of the triple Higgs coupling below HL-LHC sensitivies. The required scale of new physics to effectuate a strong-enough first order phase transition can change by as much as twenty percent as the expansion rate increases by six orders of magnitude.

hep-ph↗

arXiv2016

Gauge fixing and renormalisation scale independence of tunneling rate in abelian Higgs model and in the Standard Model

We explicitly show perturbative gauge fixing independence of the tunneling rate to a stable radiatively induced vacuum in the abelian Higgs model. We work with a class of $R_ξ$ gauges in the presence of both dimensionless and dimensionful gauge fixing parameters. We show that Nielsen identities survive the inclusion of higher order oparators and compute the tunnelling rate to the vacua modified by the nonrenormalisable operators in a gauge invariant manner. We also discuss implications of this method for the complete Standard Model.

hep-ph↗

arXiv2015

Saddle point inflation from higher order corrections to Higgs/Starobinsky inflation

We explore two saddle point inflationary scenarios in the context of higher order corrections related to different generalisations of general relativity. Firstly, we deal with Jordan frame Starobinsky potential, for which we identify a portion of a parameter space of inflection point inflation, which can accommodate all the experimental results. Secondly, we analyse Higgs inflation and more specifically the influence of non-renormalisible terms on the standard quartic potential. All results were verified with the PLANCK 2015 data.

hep-th↗

arXiv2015

Features of electroweak symmetry breaking in five dimensional SUSY models

We explore the phenomenological predictions of a supersymmetric standard model, with a large extra dimension and unifying gauge couplings. The modified five dimensional renormalisation group equations make it possible to obtain light, maximally mixed stops, with a low scale of supersymmetry breaking and a low unification scale. This allows the fine-tuning to be lowered right down to the barrier coming directly from experimental lower limits on the stop masses. We also show that attempts at modifying the SUSY breaking pattern to obtain more natural soft terms at the high scale do not give the expected fine-tuning relaxation, and only RGE effects turn out to be effective in generating a lower fine-tuning.

hep-ph↗