We study the elliptic flow coefficient v_2(eta,b) in Au+Au collisions at sqrt(s)=200 A GeV as a function of pseudorapidity eta and impact parameter b. Using a hybrid approach which combines early ideal fluid dynamical evolution with late hadronic rescattering, we demonstrate strong dissipative effects from the hadronic rescattering stage on the elliptic flow. With Glauber model initial conditions, hadronic dissipation is shown to be sufficient to fully explain the differences between measured v_2 values and ideal hydrodynamic predictions. Initial conditions based on the Color Glass Condensate model generate larger elliptic flow and seem to require additional dissipation during the early quark-gluon plasma stage in order to achieve agreement with experiment.

We investigate the chiral phase transition at nonzero temperature $T$ and baryon-chemical potential $\mu_B$ within the framework of the linear sigma model and the Nambu-Jona-Lasinio model. For small bare quark masses we find in both models a smooth crossover transition for nonzero $T$ and $\mu_B=0$ and a first order transition for T=0 and nonzero $\mu_B$. We calculate explicitly the first order phase transition line and spinodal lines in the $(T,\mu_B)$ plane. As expected they all end in a critical point. We find that, in the linear sigma model, the sigma mass goes to zero at the critical point. This is in contrast to the NJL model, where the sigma mass, as defined in the random phase approximation, does not vanish. We also compute the adiabatic lines in the $(T,\mu_B)$ plane. Within the models studied here, the critical point does not serve as a ``focusing'' point in the adiabatic expansion.

Stochastic thermodynamics is the field of study relating fluctuations in stochastic systems to thermodynamic quantities. The total entropy production (EP), is central to the thermodynamic classification of systems. Non-equilibrium systems manifestly all have non-zero EP and therefore impose an "arrow of time". Thermodynamic inequalities are lower bounds on the total EP and are especially useful when only parts of systems are operationally accessible. We use a stochastic calculus approach to directly derive and generalise three classes of inequalities for Markov jump processes using correlations of path observables, e.g., currents and densities. Our theoretical predictions are compared with simulations, where a good agreement is observed. The thermodynamic bounds we investigate include the thermodynamic uncertainty relation (TUR), thermodynamic transport bound (TB), and thermodynamic correlation bound (CB). We provide insight into the saturation conditions for these bounds and to what degree saturation can be achieved. Additionally, for the TUR and TB, we show how the bounds are related, which includes identifying a diffusion coefficient for jump dynamics. %An example using a toy model shows how the CB may yield a negative lower bound on the total entropy production, contrary to the non-negative bound that the TUR and TB yield. Comparisons are drawn between the TUR and TB for relaxation and stationary processes in biologically relevant settings. Specifically, calmodulin folding dynamics and secondary active transport, where differences in long-time relaxation and convergence are observed. For a systematic way to construct models, we formulate two methods to drive systems out of equilibrium without changing the stationary probability distribution.

The iS3D particlization module simulates the emission of hadrons from heavy-ion collisions via Monte-Carlo sampling of the Cooper-Frye formula which converts fluid dynamical information into local phase-space distributions for hadrons. The code package includes multiple choices for the non-equilibrium correction to these distribution functions: the 14-moment approximation, first-order Chapman-Enskog expansion, and two types of modified equilibrium distributions. This makes it possible to explore to what extent heavy-ion experimental data are sensitive to different choices for $\delta f_n$, presently the main source of theoretical uncertainty in the particlization stage. We validate our particle sampler with a high degree of precision by generating several million hadron emission events from a longitudinally boost-invariant hypersurface and comparing the event-averaged particle spectra and space-time distributions to the Cooper-Frye formula.

We extend the concept of superadiabatic dynamics, or transitionless quantum driving, to quantum open systems whose evolution is governed by a master equation in the Lindblad form. We provide the general framework needed to determine the control strategy required to achieve superadiabaticity. We apply our formalism to two examples consisting of a two-level system coupled to environments with time-dependent bath operators.

This work proposes a minimal model extending the duality between classical statistical spin systems and fermionic systems beyond the case of free fermions. A Jordan-Wigner transformation applied to a two-dimensional tensor network maps the partition sum of a classical statistical mechanics model to a Grassmann variable integral, structurally similar to the path integral for interacting fermions in two dimensions. The resulting model is simple, featuring only two parameters: one governing spin-spin interaction (dual to effective hopping strength in the fermionic picture), the other measuring the deviation from the free fermion limit. Nevertheless, it exhibits a rich phase diagram, partially stabilized by elements of topology, and featuring three phases meeting at a tricritical point. Besides the interpretation as a spin and fermionic system, the model is closely related to loop gas and vertex models and can be interpreted as a parity-preserving (non-unitary) circuit. Its minimal construction makes it an ideal reference system for studying non-linearities in tensor networks and deriving results by means of duality.

It is well known that the equation of state (EoS) of compact objects like neutron and quark stars is not determined despite there are several sophisticated models to describe it. From the electromagnetic observations, summarized in \cite{Lattimer01}, and the recent observation of gravitational waves from binary neutron star inspiral GW170817 \cite{Abbott2017_etal} and GW190425 \cite{Abbott2019}, it is possible to make an estimation of the range of masses and so constraint the mass of the neutron and quark stars, determining not only the best approximation for the EoS, but which kind of stars we would be observing. In this paper we explore several configurations of neutron stars assuming a simple polytropic equation of state, using a single layer model without crust. In particular, when the EoS depends on the mass rest density, $p=K \rho_{0}^{\Gamma}$, and when it depends on the energy density $p=K \rho^{\Gamma}$, considerable differences in the mass-radius relationships are found. On the other hand, we also explore quark stars models using the MIT bag EoS for different values of the vacuum energy density $B$.

A serious concern for semi-analytical galaxy formation models, aiming to simulate multi-wavelength surveys and to thoroughly explore the model parameter space, is the extremely time consuming numerical solution of the radiative transfer of stellar radiation through dusty media. To overcome this problem, we have implemented an artificial neural network algorithm in the radiative transfer code GRASIL, in order to significantly speed up the computation of the infrared SED. The ANN we have implemented is of general use, in that its input neurons are defined as those quantities effectively determining the shape of the IR SED. Therefore, the training of the ANN can be performed with any model and then applied to other models. We made a blind test to check the algorithm, by applying a net trained with a standard chemical evolution model (i.e. CHE_EVO) to a mock catalogue extracted from the SAM MORGANA, and compared galaxy counts and evolution of the luminosity functions in several near-IR to sub-mm bands, and also the spectral differences for a large subset of randomly extracted models. The ANN is able to excellently approximate the full computation, but with a gain in CPU time by $\sim 2$ orders of magnitude. It is only advisable that the training covers reasonably well the range of values of the input neurons in the application. Indeed in the sub-mm at high redshift, a tiny fraction of models with some sensible input neurons out of the range of the trained net cause wrong answer by the ANN. These are extreme starbursting models with high optical depths, favorably selected by sub-mm observations, and difficult to predict a priori.

The observations of GW170817/GRB170817A have confirmed that the coalescence of a neutron-star binary is the progenitor of a short gamma-ray burst. In the standard picture of a short gamma-ray burst, a collimated highly relativistic outflow is launched after merger and it successfully breaks out from the surrounding ejected matter. Using initial conditions inspired from numerical-relativity binary neutron-star merger simulations, we have performed general-relativistic hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations in which the jet is launched and propagates self-consistently. The complete set of simulations suggests that: (i) MHD jets have an intrinsic energy and velocity polar structure with a ``hollow core'' subtending an angle $\theta_{\rm core}\approx4^{\circ}-5^{\circ}$ and an opening angle of $\theta_{\rm jet}\gtrsim10^{\circ}$; (ii) MHD jets eject significant amounts of matter and two orders of magnitude more than HD jets; (iii) the energy stratification in MHD jets naturally yields the power-law energy scaling $E(>\Gamma\beta)\propto(\Gamma\beta)^{-4.5}$; (iv) MHD jets provide fits to the afterglow data from GRB170817A that are comparatively better than those of the HD jets and without free parameters; (v) finally, both of the best-fit HD/MHD models suggest an observation angle $\theta_{\rm obs} \simeq 21^{\circ}$ for GRB170817A.

The di-top final state is an important search channel for additional Higgs bosons at the LHC. In this channel, large signal--background interference contributions can strongly distort a resonance peak as it would be expected from a pure signal contribution. Moreover, signal--signal interference effects can have a significant impact if more than one additional scalar particle is present. In this work, we perform a comprehensive model-independent analysis of the various interference contributions considering two additional heavy scalars that can mix with each other. We point out the importance of taking into account loop-level mixing between the scalars. A proper treatment of these mixing effects, which has not been previously carried out for the di-top final state, introduces additional relative phases between different parts of the amplitudes entering the interference contributions which we find to have a strong impact on the di-top invariant mass distribution. We study the interference effects both in an idealistic setting as well as taking into account experimental limitations using Monte-Carlo simulations. We demonstrate that the emerging experimental signatures can be unexpected and difficult to interpret. In particular, we point out that an experimental signature manifesting itself as an excess near the $t \bar t$ threshold may actually be caused by new scalar particles with much higher masses. We comment in this context on the recent excess that has been observed by the CMS collaboration near the $t \bar t$ threshold in their searches in the di-top final state.

For a generic quantum many-body system, the quantum ergodic regime is defined as the limit in which the spectrum of the system resembles that of a random matrix theory (RMT) in the corresponding symmetry class. In this paper we analyse the time dependence of correlation functions of operators. We study them in the ergodic limit as well as their approach to the ergodic limit which is controlled by non-universal massive modes. An effective field theory (EFT) corresponding to the causal symmetry and its breaking describes the ergodic phase. We demonstrate that the resulting Goldstone-mode theory has a topological expansion, analogous to the one described in arXiv:2008.02271 with added operator sources, whose leading non-trivial topologies give rise to the universal ramp seen in correlation functions. The ergodic behaviour of operators in our EFT is seen to result from a combination of RMT-like spectral statistics and Haar averaging over wave-functions. Furthermore we analytically capture the plateau behaviour by taking into account the contribution of a second saddle point. Our main interest are quantum many-body systems with holographic duals and we explicitly establish the validity of the EFT description in the SYK-class of models, starting from their microscopic description. By studying the tower of massive modes above the Goldstone sector we get a detailed understanding of how the ergodic EFT phase is approached and derive the relevant Thouless time scales. We point out that the topological expansion can be reinterpreted in terms of contributions of bulk wormholes and baby-universes.

Inferring the properties of dense matter is one of the most exciting prospects from the measurement of gravitational waves from neutron star mergers. However, it will require reliable numerical simulations that incorporate viscous dissipation and energy transport if these can play a significant role within the survival time of the post-merger object. We calculate timescales for typical forms of dissipation and find that thermal transport and shear viscosity will not be important unless neutrino trapping occurs, which requires temperatures above about 10 MeV and gradients over lengthscales of 0.1 km or less. On the other hand, if direct-Urca processes remain suppressed, leaving modified-Urca processes to establish flavor equilibrium, then bulk viscous dissipation could provide significant damping to density oscillations observed right after the merger. When comparing with data from a state-of-the-art merger simulation we find that the bulk viscosity takes values close to its resonant maximum in a typical neutron-star merger, motivating a more careful assessment of the role of bulk viscous dissipation in the gravitational-wave signal from merging neutron stars.

We study the hadronic effects on the $cc\bar{q}\bar{q}$ tetraquark state by focusing on the $T_{cc}(1^+)$ meson during the hadronic stage of relativistic heavy ion collisions. We evaluate the absorption cross section of the $T_{cc}$ meson by pions in the quasi-free approximation, and investigate the time evolution of the $T_{cc}$ abundance in the hadronic medium based on the effective volume and temperature of the hadronic phase at both RHIC and LHC modelled by hydrodynamic calculations with the lattice equation of state. We probe two possible scenarios for the structure of $T_{cc}$, where it is assumed to be either a compact multiquark state or a larger sized molecular configuration composed of DD*. Our numerical results suggest that the hadronic effects on the $T_{cc}$ production is insignificant, and its final abundance depends on the initial yield of $T_{cc}$ produced from the quark-gluon plasma phase, which will depend on the assumed structure of the state.

Magnetohydrodynamics of strongly magnetized relativistic fluids is derived in the ideal and dissipative cases, taking into account the breaking of spatial symmetries by a quantizing magnetic field. A complete set of transport coefficients, consistent with the Curie and Onsager principles, is derived for thermal conduction, as well as shear and bulk viscosities. It is shown that in the most general case the dissipative function contains five shear viscosities, two bulk viscosities, and three thermal conductivity coefficients. We use Zubarev's non-equilibrium statistical operator method to relate these transport coefficients to correlation functions of equilibrium theory. The desired relations emerge at linear order in the expansion of the non-equilibrium statistical operator with respect to the gradients of relevant statistical parameters (temperature, chemical potential, and velocity.) The transport coefficients are cast in a form that can be conveniently computed using equilibrium (imaginary-time) infrared Green's functions defined with respect to the equilibrium statistical operator.

We study Weyl semimetals in the presence of generic disorder, consisting of a random vector potential as well as a random scalar potential. We derive renormalization group flow equations to second order in the disorder strength. These flow equations predict a disorder-induced phase transition between a pseudo-ballistic weak-disorder phase and a diffusive strong-disorder phase for sufficiently strong random scalar potential or for a pure three-component random vector potential. We verify these predictions using a numerical study of the density of states near the Weyl point and of quantum transport properties at the Weyl point. In contrast, for a pure single-component random vector potential the diffusive strong-disorder phase is absent.

We introduce an event-by-event pQCD + saturation + hydro ("EKRT") framework for high-energy heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading order (NLO) perturbative QCD (pQCD) using saturation to control soft particle production, and describe the space-time evolution of the QCD matter with viscous hydrodynamics, event by event (EbyE). We compare the computed centrality dependence of hadronic multiplicities, p_T spectra and flow coefficients v_n against LHC and RHIC data. We compare also the computed EbyE probability distributions of relative fluctuations of v_n, as well as correlations of 2 and 3 event-plane angles, with LHC data. Our systematic multi-energy and -observable analysis not only tests the initial state calculation and applicability of hydrodynamics, but also makes it possible to constrain the temperature dependence of the shear viscosity-to-entropy ratio, eta/s(T), of QCD matter in its different phases. Remarkably, we can describe all these different flow observables and correlations consistently with eta/s(T) that is independent of the collision energy.

In this work we evaluate the $^1S_0$ energy gap of $\Sigma^-$ hyperons in $\beta$-stable neutron star matter. We solve the BCS gap equation for an effective $\Sigma^-\Sigma^-$ pairing interaction derived from the most recent parametrization of the hyperon-hyperon interaction constructed by the Nijmegen group. We find that the $\Sigma^-$ hyperons are in a $^1S_0$ superfluid state in the density region $\sim 0.27-0.7$ fm$^{-3}$, with a maximum energy gap of order 8 MeV at a total baryon number density of $\sim 0.37$ fm$^{-3}$ and a $\Sigma^-$ fraction of about 8%. We examine the implications on neutron star cooling.

We consider the time evolution of nonequilibrium quantum scalar fields in the O(N) model, using the next-to-leading order 1/N expansion of the 2PI effective action. A comparison with exact numerical simulations in 1+1 dimensions in the classical limit shows that the 1/N expansion gives quantitatively precise results already for moderate values of N. For sufficiently high initial occupation numbers the time evolution of quantum fields is shown to be accurately described by classical physics. Eventually the correspondence breaks down due to the difference between classical and quantum thermal equilibrium.

We investigate QCD with a large number of massless flavors with the aid of renormalization group flow equations. We determine the critical number of flavors separating the phases with and without chiral symmetry breaking in SU(Nc) gauge theory with many fermion flavors. Our analysis includes all possible fermionic interaction channels in the pointlike four-fermion limit. Constraints from gauge invariance are resolved explicitly and regulator-scheme dependencies are studied. Our findings confirm the existence of an Nf window where the system is asymptotically free in the ultraviolet, but remains massless and chirally invariant on all scales, approaching a conformal fixed point in the infrared. Our prediction for the critical number of flavors of the zero-temperature chiral phase transition in SU(3) is Nf^{cr}=10.0\pm 0.29(fermion)[+1.55;-0.63](gluon), with the errors arising from approximations in the fermionic and gluonic sectors, respectively.

String theory suggests the existence of a minimum length scale. An exciting quantum mechanical implication of this feature is a modification of the uncertainty principle. In contrast to the conventional approach, this generalised uncertainty principle does not allow to resolve space time distances below the Planck length. In models with extra dimensions, which are also motivated by string theory, the Planck scale can be lowered to values accessible by ultra high energetic cosmic rays (UHECRs) and by future colliders, i.e. $M_f\approx$ 1 TeV. It is demonstrated that in this novel scenario, short distance physics below $1/M_f$ is completely cloaked by the uncertainty principle. Therefore, Planckian effects could be the final physics discovery at future colliders and in UHECRs. As an application, we predict the modifications to the $e^+e^- \to f^+f^-$ cross-sections.