arXiv subjects

Kimmo Tuominen

Publications and source records attributed to Kimmo Tuominen.

At least 37 records · Page 2Linked to original sources

arXiv2022

Propagating Quantum Microwaves: Towards Applications in Communication and Sensing

The field of propagating quantum microwaves has started to receive considerable attention in the past few years. Motivated at first by the lack of an efficient microwave-to-optical platform that could solve the issue of secure communication between remote superconducting chips, current efforts are starting to reach other areas, from quantum communications to sensing. Here, we attempt at giving a state-of-the-art view of the two, pointing at some of the technical and theoretical challenges we need to address, and while providing some novel ideas and directions for future research. Hence, the goal of this paper is to provide a bigger picture, and -- we hope -- to inspire new ideas in quantum communications and sensing: from open-air microwave quantum key distribution to direct detection of dark matter, we expect that the recent efforts and results in quantum microwaves will soon attract a wider audience, not only in the academic community, but also in an industrial environment.

quant-ph↗

arXiv2021

SU(2) gauge theory with $N_f=24$ quarks at non-zero mass

We study SU(2) gauge field theory with $N_f=24$ quarks. The theory is asymptotically non-free and, at vanishing quark mass, governed by a Gaussian fixed point at long distances. On the other hand, at non-zero quark mass the quarks are expected to decouple at long distances and the system behaves like confining pure gauge SU(2) theory. We study the mass spectrum of the theory as the quark mass is varied and obtain scaling laws for meson masses and string tension. We also measure the evolution of the coupling constant at non-zero quark mass with gradient flow method. We observe unambiguously the decoupling of the quarks with the associated change of evolution of the coupling constant.

hep-lat↗

arXiv2021

CP-violating inflation and its cosmological imprints

We study models with several $SU(2)$ scalar doublets where the inert doublets have a non-minimal coupling to gravity and play the role of the inflaton. We allow for this coupling to be complex, thereby introducing CP-violation -- a necessary source of the baryon asymmetry -- in the Higgs-inflaton couplings. We investigate the inflationary dynamics of the model and discuss how the CP-violation of the model is imprinted on the particle asymmetries after inflation in the hot big bang universe.

hep-ph↗

arXiv2021

Spectrum of SU(2) gauge theory at large number of flavors

We present a numerical study of the spectrum of an asymptotically non-free $SU(2)$ gauge theory with $N_f=24$ massive fermion flavors. For such large number of flavors, asymptotic freedom is lost and the massless theory is governed by a gaussian fixed point at long distances. If fermions are massive they decouple at low energy scales and the theory is confining. We present a scaling law for the masses of the hadrons, glueballs and string tension as functions of fermion mass. The hadrons become effectively heavy quark systems, with masses approximately twice the fermion mass, whereas the energy scale of the confinement, probed by e.g. the string tension, is much smaller and vanishes asymptotically as $m_\text{fermion}^{2.18}$. Our results from lattice simulations are compatible with this behaviour.

hep-lat↗

arXiv2021

Solar neutrinos and dark matter detection with diurnal modulation

We investigate the diurnal modulation of the event rate for dark matter scattering on solid targets arising from the directionally dependent defect creation threshold energy. In particular, we quantify how this effect would help in separating dark matter signal from the neutrino background. We perform a benchmark analysis for a germanium detector and compute how the reach of the experiment is affected by including the timing information of the scattering events. We observe that for light dark matter just above the detection threshold the magnitude of the annual modulation is enhanced. In this mass range using either the annual or diurnal modulation information provides a similar gain in the reach of the experiment, while the additional reach from using both effects remains modest. Furthermore, we demonstrate that if the background contains a feature exhibiting an annual modulation similar to the one observed by DAMA experiment, the diurnal modulation provides for an additional handle to separate dark matter signal from the background.

hep-ph↗

arXiv2020

Pseudo-Goldstone dark matter: gravitational waves and direct-detection blind spots

Pseudo-Goldstone dark matter is a thermal relic with momentum-suppressed direct-detection cross section. We study the most general model of pseudo-Goldstone dark matter arising from the complex-singlet extension of the Standard Model. The new U(1) symmetry of the model is explicitly broken down to a CP-like symmetry stabilising dark matter. We study the interplay of direct-detection constraints with the strength of cosmic phase transitions and possible gravitational-wave signals. While large U(1)-breaking interactions can generate a large direct-detection cross section, there are blind spots where the cross section is suppressed. We find that sizeable cubic couplings can give rise to a first-order phase transition in the early universe. We show that there exist regions of the parameter space where the resulting gravitational-wave signal can be detected in future by the proposed Big Bang Observer detector.

hep-ph↗

arXiv2020

Quasinormal modes and thermalization in Improved Holographic QCD

Following a series of similar calculations in simpler non-conformal holographic setups, we determine the quasinormal mode spectrum for an operator dual to a gauge-invariant scalar field within the Improved Holographic QCD framework. At temperatures somewhat above the critical temperature of the deconfinement transition, we find a small number of clearly separated modes followed by a branch-cut-like structure parallel to the real axis, the presence of which is linked to the form of the IHQCD potential employed. The temperature dependence of the lowest nonzero mode is furthermore used to study the thermalization time of the corresponding correlator, which is found to be of the order of the inverse critical temperature near the phase transition and decrease slightly faster than $1/T$ at higher temperatures.

hep-ph↗

arXiv2019

Safety versus triviality on the lattice

We present the first numerical study of the ultraviolet dynamics of non-asymptotically free gauge-fermion theories at large number of matter fields. As testbed theories we consider non-abelian SU(2) gauge theories with 24 and 48 Dirac fermions on the lattice. For these number of flavors asymptotic freedom is lost and the theories are governed by a gaussian fixed point at low energies. In the ultraviolet they can develop a physical cutoff and therefore be trivial, or achieve an interacting safe fixed point and therefore be fundamental at all energy scales. We demonstrate that the gradient flow method can be successfully implemented and applied to determine the renormalized running coupling when asymptotic freedom is lost. Additionally, we prove that our analysis is connected to the gaussian fixed point as our results nicely match with the perturbative beta function. Intriguingly, we observe that it is hard to achieve large values of the renormalized coupling on the lattice. This might be an early sign of the existence of a physical cutoff and imply that a larger number of flavors is needed to achieve the safe fixed point. A more conservative interpretation of the results is that the current lattice action is unable to explore the deep ultraviolet region where safety might emerge. Our work constitutes an essential step towards determining the ultraviolet fate of non asymptotically free gauge theories.

hep-lat↗

arXiv2019

Safe Glueballs and Baryons

We consider a non-Abelian gauge theory with $N_f$ fermions and discuss the possible existence of a non-trivial UV fixed point at large $N_f$. Specifically, we study the anomalous dimension of the (rescaled) glueball operator $\text{Tr}\ F^2$ to first order in $1/N_f$ by relating it to the derivative of the beta function at the fixed point. At the fixed point the anomalous dimension violates its unitarity bound and so the (rescaled) glueball operator is either decoupled or the fixed point does not exist. We also study the anomalous dimensions of the two spin-$1/2$ baryon operators to first order in $1/N_f$ for an $SU(3)$ gauge theory with fundamental fermions and find them to be relatively small and well within their associated unitarity bounds.

hep-th↗

arXiv2019

Velocity Dependent Dark Matter Interactions in Single-Electron Resolution Semiconductor Detectors with Directional Sensitivity

We investigate the velocity and recoil momentum dependence of dark matter interactions with ordinary matter. In particular we focus on the single-electron resolution semiconductor detectors, which allow experimental assessment of sub-GeV dark matter masses. We find that, within a specific mass range depending on the detector material, the dark matter interactions result in a signal characterized by daily modulation. Furthermore, we find that the detailed structure of this modulation is sensitive to the velocity and momentum dependence of dark matter interactions. We identify the optimal mass range for the prevalence of these effects.

hep-ph↗

arXiv2018

Direct and indirect probes of Goldstone dark matter

There exists a general model framework where dark matter can be a vanilla WIMP-like thermal relic with a mass of ${\cal O}$(100 GeV), but it still escapes direct detection. This happens, if the dark matter particle is a Goldstone boson whose scattering with ordinary matter is suppressed at low energy due to momentum-dependent interactions. We outline general features of this type of models and analyse a simple realization of these dynamics as a concrete example. In particular, we show that although direct detection of this type of dark matter candidate is very challenging, the indirect detection can already provide relevant constraints. Future projections of the indirect-detection experiments allow for even more stringent exclusion limits and can rule out models of this type.

hep-ph↗

arXiv2018

Infrared Behaviour of SU(2) Gauge Theory with $N_f$ fundamental flavours

We review our recent results on the infrared behaviour of the SU(2) gauge theory with $N_f$ massless fundamental flavour fermions. We have analyzed the running of the coupling in SU(2) gauge theories with six and eight fermionic flavours using the gradient flow step scaling method. From the running of the coupling, we see a clear indication of an infrared stable fixed point in theories with six and eight flavours. These results are confirmed by our mass spectrum study, where we varied the number of flavours from two to six. We also compute the anomalous dimensions of mass and coupling.

hep-lat↗

arXiv2018

Infrared fixed point of SU(2) gauge theory with six flavors

We compute the running of the coupling in SU(2) gauge theory with six fermions in fundamental representation of the gauge group. We establish an infrared stable fixed point at strong coupling and measure also the anomalous dimension of the fermion mass operator at the fixed point. This theory therefore likely lies close to the boundary of the conformal window and will display novel infrared dynamics if coupled with the electroweak sector of the Standard Model.

hep-lat↗

arXiv2018

Slope of the beta function at the fixed point of SU(2) gauge theory with six or eight flavors

We consider measurement of the leading irrelevant scaling exponent $γ_g^\ast$, given by the slope of the beta function, at the fixed point of SU(2) gauge theory with six or eight flavors. We use the running coupling measured using the gradient flow method and perform the continuum extrapolation by interpolating the measured beta function. We study also the dependence of the results on different discretization of the flow. For the eight flavor theory we find $γ_g^\ast=0.19(8)_{-0.09}^{+0.21}$. Applying the same analysis also for the six flavor theory, we find $γ_g^\ast=0.648(97)_{-0.1}^{+0.16}$ consistently with the earlier analysis.

hep-lat↗

arXiv2018

Singlet scalar and 2HDM extensions of the Standard Model: CP-violation and constraints from $(g-2)_μ$ and $e$EDM

We study popular scalar extensions of the Standard Model, namely the singlet extension, the 2-Higgs doublet model (2HDM) and its extension by a singlet scalar. We focus on the contributions of the added scalars to the anomalous magnetic moment of the muon, $(g-2)_μ$ in the presence of CP-violation, and the electric dipole moment of the electron ($e$EDM) in these models. In the absence of CP-violation, CP-even and CP-odd scalars contribute with an opposite sign to the anomalous magnetic moment of the muon and as a result these models generally require very light scalars to explain the observed discrepancy in $(g-2)_μ$. We study the effect of CP-violation on the anomalous magnetic moment of the muon and its compatibility with the $e$EDM constraints. We show that given the current status of the global set of constraints applied on all values of $\cotβ$, in the CP-violating scalar extensions, there exist no viable parameter space in agreement with both $a_μ$ and $e$EDM bounds.

hep-ph↗

arXiv2018

Latest predictions from the EbyE NLO EKRT model

We present the latest results from the NLO pQCD + saturation + viscous hydrodynamics (EbyE NLO EKRT) model. The parameters in the EKRT saturation model are fixed by the charged hadron multiplicity in the 0-5 \% 2.76 TeV Pb+Pb collisions. The $\sqrt{s}$, $A$ and centrality dependence of the initial particle production follows then from the QCD dynamics of the model. This allows us to predict the $\sqrt{s}$ and $A$ dependence of the particle production. We show that our results are in an excellent agreement with the low-$p_T$ data from 2.76 TeV and 5.02 TeV Pb+Pb collisions at the LHC as well as with the data from the 200 GeV Au+Au collisions at RHIC. In particular, we study the centrality dependences of hadronic multiplicities, flow coefficients, and various flow correlations. Furthermore, the nuclear mass number dependence of the initial particle production and hydrodynamic evolution can be tested in the 5.44 TeV Xe+Xe collisions at the LHC. To this end, we show our predictions for charged particle multiplicities, and in particular, show how the deformations of the Xe nuclei reflect into the flow coefficients.

nucl-th↗

arXiv2018

From chiral symmetry breaking to conformality in SU(2) gauge theory

We compute the spectrum of SU(2) gauge theory with two, four or six Dirac fermions in the fundamental representation of the gauge group. We investigate the scaling of the meson masses as a function of the quark mass when approaching the chiral limit. We find behavior compatible with the usual pattern of chiral symmetry breaking at $N_f\le 4$ and with the existence of an infrared fixed point at $N_f=6$. In the six flavor case we determine the anomalous dimension of the quark mass operator from the spectrum and find results fully consistent with earlier analyses.

hep-lat↗

arXiv2018

Hidden strongly interacting massive particles

We consider dark matter as Strongly Interacting Massive Particles (SIMPs) in a hidden sector, thermally decoupled from the Standard Model heat bath. Due to its strong interactions, the number-changing processes of the SIMP lead to its thermalization at temperature $T_{\rm{D}}$ different from the visible sector temperature $T$, and subsequent decoupling as the Universe expands. We study the evolution of the dark SIMP abundance in detail and find that a hidden SIMP provides for a consistent framework for self-interacting dark matter. Thermalization and decoupling of a composite SIMP can be treated within the domain of validity of chiral perturbation theory unlike the simplest realizations of the SIMP, where the SIMP is in thermal equilibrium with the Standard Model.

hep-ph↗