arXiv subjects
Publications and source records attributed to Krzysztof Turzynski.
We investigate a model of a supposedly ideal clock based on the decay rate of a charged particle in circular motion in a constant magnetic field. We show that the time measured by an ideal clock depends on the acceleration. However, the effect becomes visible at an order of magnitude of 10^{28} g, therefore confirming the validity of the ideal clock hyphotesis for realistic accelerations.
We examine the question to what extent prospective detection of dark matter by direct and indirect- detection experiments could shed light on what fraction of dark matter was generated thermally via the freeze-out process in the early Universe. By simulating putative signals that could be seen in the near future and using them to reconstruct WIMP dark matter properties, we show that, in a model- independent approach this could only be achieved in a thin sliver of the parameter space. However, with additional theoretical input the hypothesis about the thermal freeze-out as the dominant mechanism for generating dark matter can potentially be verified. We illustrate this with two examples: an effective field theory of dark matter with a vector messenger and a higgsino or wino dark matter within the MSSM.
We examine axino dark matter in the regime of a low reheating temperature T_R after inflation and taking into account that reheating is a non-instantaneous process. This can have a significant effect on the dark matter abundance, mainly due to entropy production in inflaton decays. We study both thermal and non-thermal production of axinos in the context of the MSSM with ten free parameters. We identify the ranges of the axino mass and the reheating temperature allowed by the LHC and other particle physics data in different models of axino interactions. We confront these limits with cosmological constraints coming the observed dark matter density, large structures formation and big bang nucleosynthesis. We find a number of differences in the phenomenologically acceptable values of the axino mass and the reheating temperature relative to previous studies. In particular, an upper bound on the axino mass becomes dependent on T_R, reaching a maximum value at T_R~10^2 GeV. If the lightest ordinary supersymmetric particle is a wino or a higgsino, we obtain lower a limit of approximately 10 GeV for the reheating temperature. We demonstrate also that entropy production during reheating affects the maximum allowed axino mass and lowest values of the reheating temperature.
We calculate the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ in a class of recently proposed two-field no-scale inflationary models in supergravity. We show that, in order to obtain correct predictions, it is crucial to take into account the coupling between the curvature and the isocurvature perturbations induced by the noncanonical form of the kinetic terms. This coupling enhances the curvature perturbation and suppresses the resulting tensor-to-scalar ratio to the per mille level even for values of the slow-roll parameter $ε\sim 0.01$. Beyond these particular models, we emphasise that multifield models of inflation are a priori not predictive, unless one supplies a prescription for the post-inflationary era, or an adiabatic limit is reached before the end of inflation. We examine the conditions that enabled us to actually derive predictions in the models under study, by analysing the various contributions to the effective isocurvature mass in general two-field inflationary models. In particular, we point out a universal geometrical contribution that is important at the end of inflation, and which can be directly extracted from the inflationary Lagrangian, independently of a specific trajectory. Eventually, we point out that spectator fields can lead to oscillatory features in the time-dependent power spectra at the end of inflation. We demonstrate how these features can be model semi-analytically as well as the theoretical uncertainties they can entail.
We examine a scenario in which the reheating temperature $T_R$ after inflation is so low that it is comparable to, or lower than, the freeze out temperature of ordinary WIMPs. In this case the dark matter relic abundance is reduced, thus relaxing the impact of the usually strong constraint coming from the requirement that the universe does not overclose. We first re-examine the dynamics of freezeout during reheating. Next we apply a Bayesian approach to study the parameter space of the MSSM with ten free parameters, the CMSSM and the singlino-dominated regions of the NMSSM. In each case we find dramatic departures from the usually considered regime of high $T_R$, with important implications for direct detection dark matter searches. In the MSSM we examine WIMP mass range up to ~5 TeV, and find regions of bino dark matter over the whole mass range, and of higgsino dark matter with mass over a similar range but starting from the ~1 TeV value of the standard high $T_R$ scenario. We show that the prospects for bino detection strongly depend on $T_R$, while the higgsino is for the most part detectable by future one-tonne detectors. The wino, which is excluded in the standard scenario, becomes allowed again if its mass is roughly above 3.5 TeV, and can be detectable. In the CMSSM, the bino and higgsino mass ranges become more constrained although detection prospects remain similar. In the Next-to-MSSM at low enough $T_R$ wide ranges of singlino-dominated parameter space of the model become cosmologically allowed. We also study the contribution to the DM relic density from direct and cascade decays of the inflaton. Finally, we consider the case of a gravitino as dark matter. We find strong bounds from overclosure and Big Bang Nucleosynthesis, and derive lower limits on $T_R$ which depend on the gravitino mass and on the nature of the lightest ordinary superpartner.
The latest results from PLANCK impose strong constraints on features in the spectrum of the curvature perturbations from inflation. We analyse the possibility of particle production induced by sharp turns of the trajectory in field space in inflation models with multiple fields. Although the evolution of the background fields can be altered by particle production, we find rather modest changes in the power spectrum even for the most extreme case in which the entire kinetic energy of the scalar fields is converted into particles.
We investigate gravitino dark matter produced thermally at high temperatures and in decays of a long-lived sneutrino. We consider the Non-Universal Higgs Model and a generalized gauge mediation model, and in each case identify sneutrino LOSP regions of the parameter space consistent with the mass of the Higgs-like boson observed at the LHC. We apply relevant collider and cosmological bounds, including constraints from Big Bang Nucleosynthesis and from warm dark matter on large scale structures. Generally, we find allowed values of the reheating temperature TR below 10^9 GeV, i.e. somewhat smaller than the values needed for thermal leptogenesis, even with a conservative lower bound of 122 GeV on the Higgs mass. Requiring mass values closer to 126 GeV implies TR below 10^7 GeV and the gravitino mass less than 10 GeV.
We re-examine the importance of slow-roll corrections during the evolution of cosmological perturbations in models of multi-field inflation. We find that in many instances the presence of light degrees of freedom leads to situations in which next to leading order slow-roll corrections become significant. Examples where we expect such corrections to be crucial include models in which modes exit the Hubble radius while the inflationary trajectory undergoes an abrupt turn in field space, or during a phase transition. We illustrate this with two examples -- hybrid inflation and double quadratic inflation. Utilizing both analytic estimates and full numerical results, we find that corrections can be as large as 20%. Our results have implications for many existing models in the literature, as these corrections must be included to obtain accurate observational predictions -- particularly given the level of accuracy expected from CMB experiments such as Planck
The aim of this paper is to discuss phenomenological consequences of a particular unification model (Z_3 model) inspired by F-theory. The most distinctive feature of this model is a variety of (cosmologically feasible) options for the NLSP and NNLSP, beyond the usually considered benchmark scenarios.
We study models of inflation with two scalar fields and non-canonical kinetic terms, focusing on the case in which the curvature and isocurvature perturbations are strongly coupled to each other. In the regime where a heavy mode can be identified and integrated out, we clarify the passage from the full two-field model to an effectively single-field description. However, the strong coupling sets a new scale in the system, and affects the evolution of the perturbations as well as the beginning of the regime of validity of the effective field theory. In particular, the predictions of the model are sensitive to the relative hierarchy between the coupling and the mass of the heavy mode. As a result, observables are not given unambiguously in terms of the parameters of an effectively single field model with non-trivial sound speed. Finally, the requirement that the sound horizon crossing occurs within the regime of validity of the effective theory leads to a lower bound on the sound speed. Our analysis is done in an extremely simple toy model of slow-roll inflation, which is chosen for its tractability, but is non-trivial enough to illustrate the richness of the dynamics in non-canonical multi-field models.
Supersymmetric theories with gravitino dark matter generally do not allow the high reheating temperature required by thermal leptogenesis without running afoul of relic abundance or big bang nucleosynthesis constraints. We report on a successful search for parameter space that does satisfy these requirements. The main implication is the near degeneracy of the gluino with the other neutralinos in the spectrum. The leading discovery channel at the LHC for this scenario is through monojet plus missing energy events.
We argue that in models of inflation with two scalar fields and non-canonical kinetic terms there is a possibility of obtaining a red tilt of the power spectrum of curvature perturbations from noncanonicality-induced interactions between the curvature and isocurvature perturbations. We describe an extremely simple model realizing this idea, study numerically its predictions for the perturbations and discuss applications in realistic scenarios of inflation. We discuss to what extent in this model the scale of the inflationary potential can be decoupled from the amplitude of the density fluctuations.
For supersymmetric theories with gravitino dark matter, the maximal reheating temperature consistent with big bang nucleosynthesis bounds arises when the physical gaugino masses are degenerate. We consider the cases of a stau or sneutrino next-to-lightest superpartner, which have relatively less constraint from big bang nucleosynthesis. The resulting parameter space is consistent with leptogenesis requirements, and can be reached in generalized gauge mediation models. Such models illustrate a class of theories that overcome the well-known tension between big bang nucleosynthesis and leptogenesis.
In cascade inflation and some other string inflation models, collisions of mobile branes with other branes or orbifold planes occur and lead to interesting cosmological signatures. The fundamental M/string-theory description of these collisions is still lacking but it is clear that the inflaton looses part of its energy to some form of brane matter, e.g. a component of tensionless strings. In the absence of a fundamental description, we assume a general barotropic fluid on the brane, which absorbs part of the inflaton's energy. The fluid is modeled by a scalar with a suitable exponential potential to arrive at a full-fledged field theory model. We study numerically the impact of the energy transfer from the inflaton to the scalar on curvature and isocurvature perturbations and demonstrate explicitly that the curvature power spectrum gets modulated by oscillations which damp away toward smaller scales. Even though, the contribution of isocurvature perturbations decays toward the end of inflation, they induce curvature perturbations on scales that exit the horizon before the collision. We consider cases where the scalar behaves like radiation, matter or a web of cosmic strings and discuss the differences in the resulting power spectra.
We investigate O'Raifeartaigh-type models for F-term supersymmetry breaking in gauge mediation scenarios in the presence of gravity. It is pointed out that the vacuum structure of those models is such that in metastable vacua gravity mediation contribution to scalar masses is always suppressed to the level below 1 percent, almost sufficient for avoiding FCNC problem. Close to that limit, gravitino mass can be in the range 10-100 GeV, opening several interesting possibilities for gauge mediation models, including Giudice-Masiero mechanism for mu and Bmu generation. Gravity sector can include stabilized moduli.
Strictly adhering to the standard supersymmetric seesaw mechanism, we present a neutrino mass model which allows successful standard thermal leptogenesis compatible with gravitino cosmology. At least some of the neutrino Yukawa couplings must be much larger than the naive estimates following from the seesaw formula. This leads to large BR(mu->e gamma), detectable in the next round of experiments. Ratios of mu->e gamma, tau->e gamma and tau->mu gamma branching ratios are predicted in terms of the measurable neutrino mass matrix.
Several classes of neutrino mass models, which can naturally account for hierarchical masses and the bi-large pattern of neutrino mixing, are constructed from a bottom-up perspective based on the idea of decoupling of one right-chiral neutrino from the seesaw mechanism. The interplay between the predictions for the lepton-flavour violation in the MSSM with universal soft masses and for leptogenesis is studied. In particular, classes of neutrino mass models in which successful leptogenesis implies BR(mu->e gamma) potentially observable in upcoming experiments are identified.
We present predictions for flavour-violating charged-lepton decays induced by the seesaw mechanism implemented within the constrained minimal supersymmetric standard model (CMSSM) with universal input soft supersymmetry breaking terms. We assume that one heavy singlet neutrino almost decouples from the see-saw mechanism, as suggested by the pattern of light neutrino masses and mixing angles. This is suggested independently by sneutrino inflation with a low reheating temperature, T(RH)<10^7 GeV, so as to avoid overproducing gravitinos. This requirement further fixes the mass of the weakly-coupled sneutrino, whose decays may lead to leptogenesis. We find that BR(mu->e gamma)>10^(-13) but BR(tau->mu gamma)<10^(-9) in the bulk of the acceptable parameter space, apart from a few isolated points. The ratio BR(mu->e gamma)/BR(tau->mu gamma) depends on only one complex parameter, and is particularly interesting to compare with experiment.