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Kimmo Tuominen

Publications and source records attributed to Kimmo Tuominen.

122 records · Page 7Linked to original sources
arXiv2008

Spectrum of SU(2) gauge theory with two fermions in the adjoint representation

We present preliminary results of lattice simulations of SU(2) gauge theory with two Wilson fermions in the adjoint representation. This theory has recently attracted considerable attention because it might possess an infrared fixed point (or an almost-fixed-point), and hence be a candidate for a walking technicolor theory. In this work we study the particle spectrum of the theory, and compare it with more familiar spectrum of the theory with SU(2) gauge fields and two flavors of fundamental representation fermions.

hep-lat↗
arXiv2006

The WIMP of a Minimal Technicolor Theory

We consider the possibility that a massive fourth family neutrino, predicted by a recently proposed minimal technicolor theory, could be the source of the dark matter in the universe. The model has two techniflavors in the adjoint representation of an SU(2) techicolor gauge group and its consistency requires the existence of a fourth family of leptons. By a suitable hypercharge assignement the techniquarks together with the new leptons look like a conventional fourth standard model family. We show that the new (Majorana) neutrino N can be the dark matter particle if $m_N \sim 100-500$ GeV and the expansion rate of the Universe at early times is dominated by an energy component scaling as $ρ_ϕ\sim a^{-6}$ (kination), with $ρ_ϕ/ρ_{\rm rad} \sim 10^{-6}$ during the nucleosynthesis era.

hep-ph↗
arXiv2005

Orientifold theory dynamics and symmetry breaking

We show that it is possible to construct explicit models of electroweak symmetry breaking in which the number of techniflavors needed to enter the conformal phase of the theory is small and weakly dependent on the number of technicolors. Surprisingly, the minimal model with {\it just} two (techni)flavors, together with a suitable gauge dynamics, can be made almost conformal. The theories we consider are generalizations of orientifold type gauge theories, in which the fermions are in either two index symmetric or antisymmetric representation of the gauge group, as the underlying dynamics responsible for the spontaneous breaking of the electroweak symmetry. We first study their phase diagram, and use the fact that specific sectors of these theories can be mapped into supersymmetric Yang-Mills theory to strengthen our results. This correspondence allows us also to have information on part of the nonperturbative spectrum. We propose and investigate some explicit models while briefly exploring relevant phenomenological consequences. Our theories not only can be tested at the next collider experiments but, due to their simple structure, can also be studied via current lattice simulations.

hep-ph↗
arXiv2004

Tetracritical behavior in strongly interacting theories

We suggest a tetracritical fixed point to naturally occur in strongly interacting theories. As a fundamental example we analyze the temperature--quark chemical potential phase diagram of QCD with fermions in the adjoint representation of the gauge group (i.e. adjoint QCD). Here we show that such a non trivial multicritical point exists and is due to the interplay between the spontaneous breaking of a global U(1) symmetry and the center group symmetry associated to confinement. Our results demonstrate that taking confinement into account is essential for understanding the critical behavior as well as the full structure of the phase diagram of adjoint QCD. This is in contrast to ordinary QCD where the center group symmetry associated to confinement is explicitly broken when the quarks are part of the theory.

hep-ph↗
arXiv2004

Confinement versus Chiral Symmetry

We construct an effective Lagrangian which illustrates why color deconfines when chiral symmetry is restored in hot gauge theories with quarks in the fundamental representation. For quarks in the adjoint representation we show that while deconfinement and the chiral transition do not need to coincide, entanglement between them is still present. Extension to the chemical potential driven transition is discussed.

hep-ph↗
arXiv2004

Effective Lagrangians for QCD: Deconfinement and Chiral Symmetry Restoration

Effective Lagrangians for Quantum Chromodynamics (QCD) especially suited for understanding deconfinement and chiral symmetry restoration at nonzero temperature and matter density are reviewed. These effective theories allow one to study generic properties of phase transitions using non-order parameter fields without loosing the information encoded in the true order parameter. {}For the pure gauge theory we demonstrate that, near the deconfining phase transition, the center group symmetry is naturally linked to the conformal anomaly. Another relevant outcome is that when the theory contains also quarks we can explain the intertwining of chiral symmetry restoration and deconfinement for QCD with matter fields either in the fundamental or in the adjoint representation of the gauge group. As a test of our general approach we show our results to be applicable also at non zero baryon chemical potential. We also predict new testable substructures to be present in the phase diagram of quarks in the adjoint representation of the gauge group. Here we provide some new insights on the large $N$ limit of gauge theories by investigating the hadronic world. We propose that the world of infinite $N$ should already be well described when N=6 for QCD with two and three light flavors. Finally, we suggest possible future applications of our results for heavy ions collisions.

hep-ph↗
arXiv2003

Confinement, Chiral Symmetry and Hadrons

The Polyakov loop is the appropriate deconfinement order parameter for Yang-Mills theories without quarks or with quarks in the adjoint representation of the gauge group. However it is not a physical state of the theory so the information regarding the center group symmetry must be transferred to the physical states. We briefly review how this transfer of information takes place. When adding quarks the center group is no longer a symmetry for matter in the fundamental representation. This feature allows us to explain why color deconfines when chiral symmetry is restored in hot gauge theories with massless quarks. For quarks in the adjoint representation we show that while deconfinement and the chiral transition do not coincide, entanglement between them is still present. Finally, we discuss also the chemical potential driven phase transition.

hep-ph↗
arXiv2003

Confinement as Felt by Hadrons

The critical behavior of non-order parameter fields is discussed. We show that relevant features of the deconfining phase transition can be determined by monitoring universal properties induced by the order parameter on the physical excitations. Some of the behaviors we uncover are already supported by lattice results.

hep-ph↗
arXiv2003

Induced Universal Properties and Deconfinement

We propose a general strategy to determine universal properties induced by a nearby phase transition on a non-order parameter field. A general renormalizable Lagrangian is used, which contains the order parameter and a non-order parameter field, and respects all the symmetries present. We investigate the case in which the order parameter field depends only on space coordinates and the case in which this field is also time dependent. We find that the spatial correlators of the non-order parameter field, in both cases, are infrared dominated and can be used to determine properties of the phase transition. We predict a universal behavior for the screening mass of a generic singlet field, and show how to extract relevant information from such a quantity. We also demonstrate that the pole mass of the non-order parameter field is not infrared sensitive. Our results can be applied to any continuous phase transition. As an example we consider the deconfining transition in pure Yang-Mills theory, and show that our findings are supported by lattice data. Our analysis suggests that monitoring the spatial correlators of different hadron species, more specifically the derivatives of these, provides an efficient and sufficient way to experimentally uncover the deconfining phase transition and its features.

hep-ph↗
arXiv2003

Higgs Mechanism via Bose Einstein Condensation

Recently the Bose-Einstein phenomenon has been proposed as possible physical mechanism underlying the spontaneous symmetry breaking in cold gauge theories. The mechanism is natural and we use it to drive the electroweak symmetry breaking. The mechanism can be implemented in different ways while here we review two simple models in which the Bose-Einstein sector is felt directly or indirectly by all of the standard model fields. The structure of the corrections due to the new mechanism is general and independent on the model used leading to experimental signatures which can be disentangled from other known extensions of the standard model.

hep-ph↗
arXiv2003

Electroweak Symmetry Breaking via Bose-Einstein Mechanism

Recently the Bose-Einstein phenomenon has been proposed as possible physical mechanism underlying the spontaneous symmetry breaking in cold gauge theories. The mechanism is natural and we use it to drive the electroweak symmetry breaking. It can be implemented in different ways while here we present a simple model in which the Bose-Einstein sector is felt only indirectly by all of the standard model fields. The structure of the corrections due to the new mechanism is general and independent on the model used here leading to experimental signatures which can be disentangled from other known extensions of the standard model.

hep-ph↗
arXiv2003

Spontaneous symmetry breaking in gauge theories via Bose-Einstein condensation

We propose a mechanism naturally leading to the spontaneous symmetry breaking in a gauge theory. The Higgs field is assumed to have global and gauged internal symmetries. We associate a non zero chemical potential to one of the globally conserved charges commuting with all of the gauge transformations. This induces a negative mass squared for the Higgs field triggering the spontaneous symmetry breaking of the global and local symmetries. The mechanism is general and we test the idea for the electroweak theory in which the Higgs sector is extended to possess an extra global Abelian symmetry. To this symmetry we associate a non zero chemical potential. The Bose-Einstein condensation of the Higgs leads, at tree level, to modified dispersion relations for the Higgs field while the dispersion relations of the gauge bosons and fermions remain undisturbed. The latter are modified through higher order corrections. We have computed some corrections to the vacuum polarizations of the gauge bosons and fermions. To quantify the corrections to the gauge boson vacuum polarizations with respect to the Standard Model we considered the effects on the T parameter. We finally derive the one loop modified fermion dispersion relations.

hep-ph↗
arXiv2003

Critical Behavior of Non Order-Parameter Fields

We show that all of the relevant features of a phase transition can be determined using a non order parameter field which is a physical state of the theory. This fact allows us to understand the deconfining transition of the pure Yang-Mills theory via the physical excitations rather than using the Polyakov loop.

hep-ph↗