The postmerger dynamics of binary neutron-star merger events is known to be sensitive not only to the equation of state of the constituent matter, but also to its transport properties. A quantity of particular importance here is the bulk viscosity, which arises in a subtle interplay between the strong and electroweak interactions. In this talk, I will review a recent determination of the bulk...
The phase transition from hadronic to quark matter may take place already during the early post-bounce stage of core collapse supernovae and in neutron star mergers. If the phase transition is of first order, the formation of the quark matter phase occurs via the nucleation of droplets. The timescales relevant for the phase conversion dynamics, as well as the possibility of mixed phases, are...
Exploiting the first measurements of the same ion species in O+O collisons at RHIC and LHC, we propose an experimentally accessible observable to distinguish whether collective behavior builds up through a hydrodynamic expansion of a strongly interacting QGP or through few final state rescatterings. Our procedure allows to disentangle the effects of the initial state geometry and the dynamical...
We study the energy deposition and thermalisation of high-momentum on-shell partons (minijets) travelling through a non-equilibrium Quark-Gluon Plasma using QCD kinetic theory. For thermal backgrounds, we show that the parton energy first flows to the soft sector by collinear cascade and then isotropises via elastic scatterings. In contrast, the momentum deposition from a minijet reaches the...
Jet quenching measurements may provide an experimental opportunity to infer non-equilibrium properties of the quark-gluon plasma created in heavy-ion collisions. An important medium parameter determining the strength of jet-medium interactions is the jet quenching parameter $\hat q$. In this talk, I will present our results for this jet quenching parameter $\hat q$ in the initial...
The rapid longitudinal expansion characteristic of heavy-ion collisions leads to universal attractor behavior of the resulting drop of Quark-Gluon Plasma. Assuming approximate boost invariance, we incorporate transverse dynamics and parton evolution by linearizing the Israel-Stewart theory around the attractor. This yields a system of coupled ordinary differential equations which describe the...
The prospect of gravitational wave detectors observing the remnant signal of a cosmological phase transition has inspired a flurry of developments in their theoretical description. Automating these developments is needed to improve predictions for phenomenological studies of BSM models. In this talk, I will describe some key theoretical developments and discuss progress and challenges for...
With the approval of the space-based LISA experiment, the hunt is on: A search for gravitational-wave remnants of the Electroweak phase transition; to probe the Higgs potential and perchance even explain the Baryon asymmetry problem. Yet the theoretical hurdles are great—theoretical predictions can misjudge the peak gravitational-wave spectrum by orders of magnitude.
In this talk I will...
We calculated the gravitational waves induced by different QCD phase transitions including in a chirality imbalanced system, in pure gluon system, in PQM, Qm, and Friedberg-Lee model, and the gravitaitional waves can be detected by LISA, Taiji and DECIGO. We find that the values of inverse duration $\beta/H$ of these QCD phase transitions are of order $10^4$ or $10^3$, which means the phase...
I discuss how astrophysical constraints on the dense-matter equation of state place an upper bound on the color-superconducting gap in dense matter above the transition from nuclear matter to quark matter. Pairing effects in the color-flavor locked (CFL) quark matter phase increase the pressure at high density, and if this effect is sufficiently large then the requirements of causality and...
Deconfined quark matter at asymptotically high densities is weakly coupled, due to the asymptotic freedom of QCD. In this weak-coupling regime, bulk thermodynamic properties of quark matter, assuming a trivial ground state, are currently known to partial next-to-next-to-next-to-leading order. However, the ground state at high densities is expected to be a color superconductor, in which the...
Electroweak Theory (EWT) allows the existence of BNV processes mediated by topologically non-trivial field configurations. The most well-known such configuration is the instanton. However, due to the breaking of scale invariance by the Higgs mass, instantons are not allowed in EWT. Instead, one must use constrained instantons to obtain the BNV rate.
This poster will explain constrained...
The order of the thermal chiral phase transition in lattice QCD is strongly cutoff-dependent. A recent study from our group using mass-degenerate, unimproved staggered quarks on $N_\tau=\{4,6,8\}$ lattices found that the first-order regions shrink to zero for $N_\text{f}\in[2,6]$ as the continuum limit is approached for zero chemical potential. Here we present the progress of an analogous...
The shear viscosity of the quark-gluon plasma (QGP) is important ingredient for describing current measurements in heavy-ion collisions and are key inputs to hydrodynamical models. The interest in shear viscosity also lies in the fact that QGP is the most ideal fluid ever observed and has the shear viscosity to entropy ratio ($\eta / s$) close to the theoretical bound $\eta / s \geq 1/ 4 \pi$...
Jets play an important role in heavy-ion collisions, interacting with and thereby probing the quark-gluon plasma (QGP) as they propagate to the detector. The asymptotic mass, $m_{\infty}$ and the transverse scattering rate, $\mathcal{C}(k_{\perp})$ control this interaction insofar as they serve as input to calculations of transverse momentum broadening and medium-induced radiation. Both...
The nature of the QCD phase transition in the chiral limit constitutes a challenging problem for lattice QCD as it is not directly simulable. Its study, however, provides constraints on the phase diagram at the physical point. Recently, the thermal transition for massless fermions was shown to be of second order for all numbers of flavours $N_f \lesssim 7$. For this, the lattice chiral limit...
The Hamiltonian formulation of lattice QCD based on an effective theory (the so-called dual formulation) can be extended in the strong coupling limit to two flavors. It has no sign problem at both non-zero baryon and isospin densities and allows for Quantum Monte Carlo simulations. We present results on the phase boundary for the chiral transition in the $\mu_B - \mu_I$ plane in the chiral...
In this talk, I will give an overview of the universal critical dynamics at the chiral phase transition of two-flavor QCD in the chiral limit. I will review the general argument about the dynamic universality class by explicitly constructing the stochastic equations of motion in the vicinity of the second-order phase transition. To extract dynamic universal quantities associated with these...
We investigate the 2SC phase at medium baryon density using the quark-meson-diquark model. Our analysis involves calculating the thermodynamic potential in the mean field approximation to one fermion loop. The model includes the following effective degrees of freedom: the sigma, pions, quarks, and diquarks. Parameters are expressed with the physical values of the sigma mass, pion mass, and...
Employing a phenomenological nucleon-meson model, we study the possible existence of a chiral density wave in neutron star matter. We impose charge neutrality and β-equilibrium, extending previous works that studied isospin-symmetric nuclear matter. We find that the chiral density wave is energetically preferred in a region of our parameter space that predict a very soft equation of state. In...
I will present perturbative results[1] on the confinement/deconfinement transition of Yang-Mills theories found in a center-symmetric Landau gauge with a Curci-Ferrari mass term to account for IR Gribov copies. We obtained one-loop predictions for the SU(2) and SU(3) transition temperatures close to lattice values. I will show that our results are consistent across different renormalization...
In this work, we perform computations of inclusive jet and semi-inclusive jet-hadron cross sections for minimum-bias oxygen-oxygen collisions. We compute the no-quenching baseline for the jet nuclear modification factor $R_{AA}$ and jet-, and hadron-triggered semi-inclusive nuclear modification factors $I_{AA}$. We do this with state-of-the-art nuclear parton distribution functions, NLO matrix...
Neutron stars with admixed dark matter enable new possibilities in the description of unusal mass and radius measurements, such as e.g. HESS J1731-347. We are including bosonic, self-interacting dark matter with a sufficiently stiff self-interaction potential in the form of $V \propto \phi^n$ and find that these neutron stars become ultra-compact ($C \geq 1/3$). They are compact enough to have...
In the intermediate density region of the QCD phase diagram, there have been conjectures about inhomogeneous, chiral phases, i.e., phases with translational symmetry breaking through the chiral condensate. A precursor phenomenon, the so-called Moat regime, where mesonic dispersion relations favor non-vanishing momenta, was found in a recent FRG study of the QCD phase diagram in the vicinity of...
In this work we calculate the electric and magnetic susceptibilities of a hot and dense medium in equilibrium up to order $\mathcal{O}(\frac{m^4}{T^4})$ $\mathcal{O}(\frac{m^2}{T^2})$, respectively. These susceptibilities are associated with $\mathcal{O}(k^2)$ terms (power corrections) of the photon polarization tensor, which are computed here for a hot and dense medium of fermions with a...
Analyzes of astrophysical data provide hints on the self-interactions of dark matter at low energies. Lattice calculations of strongly interacting dark matter (SIMP) theories are needed for motivating these models also from first principles. Sp(4) gauge theory with two fundamental fermions is a candidate SIMP theory. We compute the scattering phase shift for the scattering of two dark pions...
Perturbative approaches to quantum field theory at finite temperature require theoretical constraints to be addressed which are not present in the vacuum theory. In this talk I will present evidence from lattice simulations of massive $\phi^4$ theory which shows that the standard perturbative predictions break down, even at relatively low temperatures. This suggests that non-perturbative...
Heavy-ion collisions are an essential tool to better understand the deconfined phase of Quark-Gluon Plasma . Probes such as heavy particles are used indirectly to study its properties. In describing the propagation of heavy particles in a medium, non-relativistic effective field theories are employed. In doing so, correlators of chromoelectric fields appear and are important in the evolution...
The thermal photon rate is an import observable for understanding the quark-gluon plasma, and can be calculated from lattice QCD by reconstructing the spectral function of the vector current correlator. Since this correlator receives a large ultraviolet contribution from the vacuum, only the thermal part of the correlator is considered, which significantly simplifies the reconstruction. Since...
Quarkonia, the bound states of heavy quark-antiquark pairs, have proven to be crucial probes for studying quark-gluon plasma (QGP). The color screening properties of the QGP weaken the interaction between quark-antiquark pairs, leading to the suppression of quarkonia yields within the QGP. We will present results on the fate of quarkonia bound states in the QGP by performing spectral...
Screening masses of states with nucleon quantum numbers are determined, for the first time, in QCD for temperatures ranging from $\sim 1$ GeV up to $\sim 160$ GeV. The non-perturbative data show that the bulk of the screening mass is given by the tree level value $3\pi T$, while interactions induce a $4 -8 \%$ positive deviation for all temperatures considered. While our results are compatible...
Exclusive C = +1 quarkonium production in high-energy electron-proton
scattering requires a C-odd t-channel exchange of a photon or three
gluons. The relative phase of the amplitudes is determined by the sign
of the light-front matrix element of the eikonal color current
operator $d^{abc} J^{+a} J^{+b} J^{+c}$. Model calculations predict
constructive interference, which is particularly...
Jet quenching plays an important role as a hard probe to study properties of the quark–gluon plasma (QGP) in heavy-ion collisions at both the relativistic heavy-ion collider and the large hadron collider. During their travel in the QGP, high energy partons lose their energy mainly through splitting processes like bremsstrahlung and pair production, induced by elastic scatterings with the...
The far-from equilibrium dynamics of the pre-hydrodynamic quark-gluon plasma (QGP) formed in heavy ion collisions can be characterized by distinct stages, during each of which the system loses some memory of its initial condition, until only the hydrodynamic modes remain. This attractor behavior has been characterized previously in both strongly and weakly coupled descriptions. In particular,...
We describe numerical simulations of stochastic fluid dynamics
with a conserved charge coupled to the momentum density of the
fluid. This theory is known as model H, and it is expected to
describe universal dynamics in the vicinity of a possible
critical endpoint in the QCD phase diagram.
Due to its phenomenological relevance in heavy-ion collisions, cosmology and astrophysics, the determination of the QCD pressure - either at high temperature or large baryon density - has driven a number of important theoretical advances in perturbative thermal field theory applicable to equilibrium thermodynamics. In particular, the long-standing infrared problems that obstruct the...
Based on the epsilon expansion of the renormalization group flows of the Ginzburg-Landau potential for the chiral phase transition of QCD, it has been widely accepted that it is of first order in the zero quark mass limit for N_f > 2, with the possibility of a second order transition for N_f = 2, given the axial anomaly remains strong enough at the critical point. Going beyond the perturbative...
We employ a model based on nucleonic and mesonic degrees of freedom to describe cold and dense matter, in order to discuss the competition between isotropic and anisotropic phases, in the region of the chiral phase transition. Anisotropic phases have been extensively studied in quark models of dense matter, but equivalent progress was lacking in models using nucleonic degrees of freedom. When...
We study the effect of rotation on the confining and chiral properties of QCD using the linear sigma model coupled to the Polyakov loop in an attempt to resolve discrepancies between the first-principle numerical and model-based analytical results. The attractive features of this model are renormalizability and the presence of the coupling between chiral and confining degrees of freedom.
We...
Some information concerning the different excursions and lists of excursion participants
Field theories with symplectic gauge group are compelling candidates for composite physics extending the Standard Model. They are of interest for both composite Dark Matter and composite Higgs models and could give rise to first-order phase transitions in the early universe. With the aim of providing a robust non-perturbative characterisation of a model of potential phenomenological relevance,...
SU($N$) pure gauge theories have a first order confinement-deconfinement phase transition when $N \ge 3$, and are prototype models for studying strongly coupled phase transitions. We use lattice simulations to determine the surface tension in SU($N$) gauge theory up to $N=16$. We observe that the surface tension $\sigma$ scales as $N^2$, and in the continuum limit can be described with...
We consider a model, where a single inflaton interacts weakly as an axion with Yang-Mills gauge bosons. As these rapidly thermalize, the friction felt by the inflaton field is increased, leading to a self-amplifying process.
If the gauge bosons of the thermal bath represent a dark sector, the reheating of the Standard Model is then realised through portal interactions.
The dark relic...
The cosmic neutrino background, for which there is ample indirect evidence, is a remnant from when the universe was just one second old. I will discuss the rate at which neutrinos interact with a QED plasma, around MeV temperatures (just prior to their decoupling). Computing the NLO interaction rate as a function of the neutrino momentum and flavour, we recently found relative corrections on...
Hot viscous plasmas unavoidably emit a stochastic gravitational wave background similar to electromagnetic black body radiation. Presenting work published in 2312.13855, we study the hidden particle contribution to the background emitted by the primordial plasma in the early universe. While this contribution can easily dominate over that from Standard Model particles, we find that both are...
The bubble wall velocity in the first order phase transition plays an important role in determining both the amplitude and the pivot frequency of stochastic gravitational wave background. In the framework of the minimal left-right symmetric model, we study the wall velocity when the first order phase transition can occur. The wall velocity can be determined by matching the distribution...
Using the imaginary part of the self-energy function in the Landau-level representation, we derive the fermion damping rate in a hot magnetized plasma at the leading order of coupling. The results are used to investigate the longitudinal and transverse electrical conductivities. In the relativistic regime, these conductivities exhibit a scaling behavior expressed in terms of dimensionless...
Scale hierarchies are required to reliably describe the thermodynamics of cosmological first-order phase transitions using perturbation theory. At finite temperature, such a hierarchy is provided naturally. One can then use this hierarchy to construct a three-dimensional effective field theory (EFT) that systematically includes thermal resummations to all orders.
Using this EFT setup, I...
In order to describe low-scale leptogenesis in the early Universe, we calculate in a beyond SM settings the measure of CP violation, which comes from the interference of a tree-level and one-loop decay amplitudes. The imaginary part of the one-loop vertex function is written using both finite temperature cutting rules of the real time formalism and analytic continuation in the imaginary time...
In high temperature and/or density plasmas, perturbative calculations typically assume massless plasma constituents. We consider small masses ($m \ll T$ or $m \ll \mu$) and compute mass corrections ($\sim m^2/T^2$ or $\sim m^2/\mu^2$) for the photon polarization tensor in a QED plasma at high temperature $T$ or chemical potential $\mu$.
To this aim, we employ EFT techniques, the so called...
For the exploration of the phase diagram of finite density QCD, effective Polyakov loop theories derived from lattice QCD provide a valuable tool in the large quark mass regime. Using mean field approximations these theories are evaluated in the high and low temperature regimes at finite baryon chemical potential. The resulting phase diagram is discussed.
Synchrotron radiation (SR) is emitted by charged particles moving in magnetic fields and has numerous applications in many areas of physics. Often the charged particles are also part of a larger rotating system, e.g. the quark-gluon plasma and rotating stars. I will show that SR exhibits a remarkable sensitivity to the angular velocity of rotation. Additionally, the size of rapidly rotating...
Our understanding of ordinary liquid matter is based on the statistical physics of Brownian motion and self-diffusion, as embodied in the complementary descriptions of Einstein and Langevin. The Langevin equation as a stochastic equation of motion which comprises all physical effects of atomic motion in liquids (from conservative interactions to dissipation) is used ubiquitously to predict the...
According to the Color Glass Condensate approach to relativistic heavy-ion collisions, the earliest phase of the collision is a glasma which is made of highly populated gluon fields that can be treated classically. Using a proper time expansion we study analytically various properties of the glasma. In particular, we compute the glasma energy-momentum tensor which allows us to obtain the...
In a strong background magnetic field, the fermionic plasma exhibits dissipationless anomalous transport, manifested as non-vanishing currents aligned with the magnetic field. This talk focuses on the novel helical separation effect (HSE), related to the emergence of a helicity current, defined by means of a suitable helicity operator, which is conserved even in the presence of the background...
We investigate the (inhomogeneous) phase structure of the Gross-Neveu model in a noninteger number of spatial dimensions 1 <= d < 3 in the limit of an infinite number of fermion species at (non)zero chemical potential and nonzero temperature.
The phase diagram of the Gross-Neveu model in 1 <= d < 3 spatial dimensions is well known under the assumption of spatially homogeneous condensation...
The complex dynamics of Quark - Gluon Plasma in its non-equillibrium state has been a hot topic since many years. One of the main aspects which lead to this complex behaviour is instabilities, generated due to the non-uniform distribution of color charges. Depending on different color modes, they can strongly influence the temporal evolution of the system. Inspired by this, we consider a...
I present a model independent framework to study gravitational waves from cosmological first-order phase transitions. This framework is based on factorisation of phase transition dynamics at infrared, in three-dimensional effective theory, and temperature dependence encoded in dimensional reduction matching relations at ultraviolet. Within an infrared EFT, leading order behaviour of transition...
The massive stars end their lives by supernova explosions leaving central compact objects that may evolve into neutron stars. Initially, after birth, the star remains hot and gradually cools down. We explore the matter and star properties during this initial stage of the compact stars considering the possibility of the appearance of deconfined quark matter in the core of the star. At the...
We compute the QCD pressure from first principles within perturbative QCD at very high magnetic fields up to next-to-leading in two different scenarios: hot quark matter and cold and dense quark matter.
We study the converge of the perturbative series for the pressure for different choices of medium dependent running coupling.
In the case of hot quark matter, we also calculate the chiral...
Understanding the thermodynamics of cold and dense QCD matter has become a prominent research topic due to recent advances in neutron-star observations. Unfortunately, the notorious Sign Problem impedes the study of such matter using lattice QCD.
However, nonperturbative inequalities constrain the pressure of dense QCD with its phase-quenched counterpart, a Sign-Problem-free theory that is...
Two-dimensional QCD was first studied by G. 't Hooft as a model for mesons in the limit of an infinite number of colours where it admits an exact solution. We investigate the model with the FRG at finite number of colours in the vacuum and present the first stages of our study towards dynamical hadronization in this model. In particular, we derive how local four-fermion interactions emerge...
At nonzero isospin chemical potential, in addition to the usual hadronic and quark-gluon plasma phases, a pion condensed phase appears in the QCD phase diagram, bounded by a second-order transition line. This setup is sign-problem-free and can be studied using standard lattice Monte-Carlo methods. An overview of the phase diagram and the possible applications of finite isospin simulation...
In certain models of inflation, the postinflationary reheating of the Universe is not primarily due to perturbative decay of the inflaton field into particles, but proceeds through a tachyonic instability. In the process, long-wavelength modes of an unstable field, which is often distinct from the inflaton itself, acquire very large occupation numbers, which are subsequently redistributed into...
Anomaly induced transport phenomena, such as the Chiral Vortical Effect (CVE) and Chiral Vortical Separation Effect (CVSE), are expected to appear in systems with vector and axial symmetries under rotation, and their coherent interplay gives rise to the so-called Chiral Vortical Wave (CVW). In this talk, we generalise the previous studies to include an independent conserved charge for a system...
