We study the effects of heavy quarks on the equation of state for cold and dense quark matter obtained from perturbative QCD, yielding observables parametrized only by the renormalization scale. We investigate the thermodynamics of charm quark matter under the constraints of $\beta$ equilibrium and electric charge neutrality in a region of densities where perturbative QCD is, in principle, much more reliable. We also analyze the stability of charm stars, which might be realized as a new branch of ultradense hybrid compact stars, and find that such quark stars are unstable under radial oscillations.

A search for heavy neutral Higgs bosons produced in association with one or two $b$-quarks and decaying to $b$-quark pairs is presented using $27.8{\mathrm{fb}}^{-1}$ of $\sqrt{s}=13\mathrm{TeV}$ proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider during 2015 and 2016. No evidence of a signal is found. Upper limits on the heavy neutral Higgs boson production cross section times its branching ratio to $b\overline{b}$ are set, ranging from 4.0 to 0.6 pb at 95% confidence level over a Higgs boson mass range of 450 to 1400 GeV. Results are interpreted within the two-Higgs-doublet model and the minimal supersymmetric Standard Model.

The axionic weak gravity conjecture predicts the existence of instantons whose actions are less than their charges in appropriate units. We show that the conjecture is satisfied for the axion-dilaton-gravity system if we assume duality constraints on the higher derivative corrections in addition to positivity bounds which follow from unitarity, analyticity, and locality of UV scattering amplitudes. On the other hand, the conjecture does not follow if we assume the positivity bounds only. This presents an example where derivation of the weak gravity conjecture requires more detailed UV information than the consistency of scattering amplitudes.

We present a practical method for evaluating the scattering amplitude $f_s(\theta ,\varphi )$ that arises in the context of the scattering of scalar, electromagnetic, and gravitational planar waves by a rotating black hole. The partial-wave representation of $f_s$ is a divergent series, but $f_s$ itself diverges only at a single point on the sphere. Here we show that $f_s$ can be expressed as the product of a reduced series and a prefactor that diverges only at this point. The coefficients of the reduced series are found iteratively as linear combinations of those in the original series, and the reduced series is shown to have amenable convergence properties. This series-reduction method has its origins in an approach originally used in electron scattering calculations in the 1950s, which we have extended to the axisymmetric context for all bosonic fields.

The marked power spectrum is capable of placing far tighter constraints on cosmological parameters (particularly the neutrino mass) than the conventional power spectrum. What new information does it contain beyond conventional statistics? Through the development of a perturbative model, we find that the mark induces a significant coupling between non-Gaussianities, which are usually found on small scales, and large scales, leading to the additional information content. The model is derived in the context of one-loop perturbation theory and validated by comparison to $N$-body simulations across a variety of mark parameters. At moderate redshifts, including for massive neutrino cosmologies, the theory is in good agreement with the simulations. The importance of nonlinear gravitational effects on the large-scale spectra complicates the modeling as there is no well-defined convergence radius of the theory at low $z$. Extension to higher perturbative order and biased tracers is possible via a similar approach, and a simple model of the latter is shown to yield promising results. The theory becomes nonperturbative at redshift zero for small smoothing scales, with important contributions from higher-order terms: these will need to be studied before the full power of this tool can be realized.

Exothermic scatterings of dark matter (DM) produce DM particles with significant kick velocities inside DM halos. In collaboration with DM self-interaction, the excess kinetic energy of the produced DM particles is distributed to the others, which self-heats the DM particles as a whole. The DM self-heating is efficient towards the halo center, and the heat injection is used to enhance the formation of a uniform density core inside halos. The effect of DM self-heating is expected to be more significant in smaller halos for two reasons: 1) the exothermic cross section times the relative velocity, $⟨{\sigma }_{\mathrm{exo}}{v}_{\mathrm{rel}}⟩$, is constant; 2) and the ratio of the injected heat to the velocity dispersion squared gets larger toward smaller-size halos. For the first time, we quantitatively investigate the core formation from DM self-heating for halos in a wide mass range (${10}^9–{10}^{15}{\mathrm{M}}_{\odot }$) using the gravothermal fluid formalism. Notably, we demonstrate that the core formation is sharply escalating toward smaller-size halos by taking the self-heating DM (i.e., DM that semiannihilates and self-interacts) as an example. We show that the sharp escalation of the core formation may cause a tension in simultaneously explaining the observed central mass deficit of Milky Way satellites and field dwarf/low surface brightness spiral galaxies. We expect DM self-heating to be present also in other models that exhibit exothermic scatterings and self-interaction of DM, which can appreciably contribute to the core formation of DM halos.

In the framework of the Standard Model extension (SME), we present improved constraints on anisotropic Lorentz invariance and charge-parity-time ($CPT$) violation by searching for astrophysical signals of cosmic vacuum birefringence with broadband optical polarimetry of high redshift astronomical sources, including active galactic nuclei and gamma-ray burst afterglows. We generalize the reference [F. Kislat, Symmetry 10, 596 (2018)], which studied the SME mass dimension $d=4$ case, to the arbitrary mass dimension for both the $CPT$-even and the $CPT$-odd cases. We then present constraints on all 10, 16, and 42 anisotropic birefringent SME coefficients for dimension $d=4$, $d=5$, and $d=6$ models, respectively, using 7554 observations for odd $d$ and 7376 observations for even $d$ of 1278 unique sources on the sky, which, to our knowledge, comprises the most complete catalog of optical polarization from extragalactic sources in the literature to date. Compared to the smaller sample of 44 and 45 broadband optical polarimetry observations analyzed in Kislat [Symmetry 10, 596 (2018)] and Kislat and Krawczynski [Phys. Rev. D 95, 083013 (2017)], our dimension $d=4$ and $d=5$ average constraints are more sensitive by factors of 35 and 10, corresponding to a reduction in allowed SME parameter space volume for these studies of 15 and 16 orders of magnitude, respectively. Constraints from individual lines of sight can be significantly stronger using spectropolarimetry, due to the steep energy dependence of birefringence effects at increasing mass dimension. Nevertheless, due to the increased number of observations and lines of sight in our catalog, our average $d=4$ and $d=5$ broadband constraints are within factors of 2 and 12 of previous constraints using spectropolarimetry from Kislat [Symmetry 10, 596 (2018)] and Kislat and Krawczynski [Phys. Rev. D 95, 083013 (2017)], respectively, using an independent dataset and an improved analysis method. By contrast, our anisotropic constraints on all 42 birefringent SME coefficients for $d=6$ are the first to be presented in the literature.

We evaluate the finite temperature scalar sunset diagram with imaginary square masses, that appears in the Gribov-Zwanziger approach to Yang-Mills (YM) theory beyond one-loop order. Since YM theory at finite temperature is governed by center-symmetry and the Polyakov loop, we also include the possibility of a constant temporal background gauge field in the form of color-dependent imaginary chemical potentials.

The $P_c(4312)$, $P_c(4440)$, and $P_c(4457)$ observed by the LHCb collaboration are very likely to be $S$-wave ${\mathrm{\Sigma }}_c{\overline{D}}^{(*)}$ molecular candidates due to their near threshold character. In this work, we study the hidden-charm decay modes of these $P_c$ states, $P_c\to J/\psi p({\eta }_{c}p)$, using a quark interchange model. The decay mechanism for the $P_c\to J/\psi p({\eta }_{c}p)$ processes arises from the quark-quark interactions, where all parameters are determined by the mass spectra of mesons. We present our results in two scenarios. In scenario I, we perform the dynamical calculations and treat the $P_c$ states as pure ${\mathrm{\Sigma }}_c{\overline{D}}^{(*)}$ molecules. In scenario II, after considering the coupled channel effect between different flavor configurations ${\mathrm{\Sigma }}_c^{(*)}{\overline{D}}^{(*)}$, we calculate these partial decay widths again. The decay patterns in these two scenarios can help us to explore the molecular assignment and the inner flavor configurations for the $P_c$ states. In particular, the decay widths of $\mathrm{\Gamma }(P_c(4312)\to {\eta }_{c}p)$ are comparable to the $J/\psi p$ decay widths in both of these two scenarios. Future experiments like LHCb may confirm the existence of the $P_c(4312)$ in the ${\eta }_{c}p$ channel.

High-luminosity fixed target experiments provide impressive sensitivity to new light weakly coupled degrees of freedom. We revisit the minimal case of a scalar singlet $S$ coupled to the Standard Model through the Higgs portal that decays visibly to leptons for scalar masses below the dipion threshold. The dataset from the LSND experiment is found to impose the leading constraints within two mass windows between $m_S\sim 100$ and 350 MeV. In the process, we analyze a number of scalar production channels in the target, finding that proton bremsstrahlung provides the dominant channel at LSND beam energies.

The large density of gluons, which is present shortly after a nuclear collision at very high energies, can lead to the formation of a condensate. We identify a gauge-invariant order parameter for condensation based on elementary nonperturbative excitations of the plasma, which are described by spatial Wilson loops. Using real-time lattice simulations, we demonstrate that a self-similar transport process towards low momenta builds up a macroscopic zero mode. Our findings reveal intriguing similarities to recent discoveries of condensation phenomena out of equilibrium in table-top experiments with ultracold Bose gases.

We propose a grading protocol that assigns global symmetry associated phases to states in the Hilbert space. Without modifying the Hilbert space, this changes the state sum, a process that we call quantum distillation. We describe the image of quantum distillation in terms of (nondynamical) flavor holonomy dependence of (dynamical) gauge-holonomy potentials, in QCD with $N_f=N_c$ fundamental and one massive adjoint fermion on ${\mathbb{R}}^3\times S^1$. The compactified theory possesses an exact zero-form color-flavor center symmetry for a special choice of flavor holonomy (under which Polyakov loop is charged), despite the absence of one-form center symmetry. We prove that the color-flavor center symmetry is stable at small $\beta$. This is the opposite of the high-temperature limit of thermal theory and a dramatic manifestation of quantum distillation. We show chiral symmetry breaking at small $S^1$ and that the vacuum structure of the theory on ${\mathbb{R}}^4$ and ${\mathbb{R}}^3\times S^1$ are controlled by the same mixed ’t Hooft anomaly condition.

A search for the production of a narrow-width resonance decaying into a pair of Higgs bosons decaying into the $bbZZ$ channel is presented. The analysis is based on data collected with the CMS detector during 2016, in proton-proton collisions at the LHC, corresponding to an integrated luminosity of $35.9{\mathrm{fb}}^{-1}$. The final states considered are the ones where one of the $Z$ bosons decays into a pair of muons or electrons, and the other $Z$ boson decays to either a pair of quarks or a pair of neutrinos. Upper limits at 95% confidence level are placed on the production of narrow-width spin-0 or spin-2 particles decaying to a pair of Higgs bosons, in models with and without an extended Higgs sector. For a resonance mass range between 260 and 1000 GeV, limits on the production cross section times branching fraction of a spin-0 and spin-2 resonance range from 0.1 to 5.0 pb and 0.1 to 3.6 pb, respectively. These results set limits in parameter space in bulk Randall-Sundrum radion, Kaluza-Klein excitation of the graviton, and next-to-minimal two-Higgs doublet models (N2HDMs). For specific choices of parameters the N2HDM can be excluded in a mass range between 360 and 620 GeV for a resonance decaying to two Higgs bosons. This is the first search for Higgs boson resonant pair production in the $bbZZ$ channel.

In this work, we consider a nonquadratic dilaton $\mathrm{\Phi }(z)=(\kappa z{)}^{2-\alpha }$ in the context of the static soft wall model to describe the mass spectrum of a wide range of vector mesons from the light up to the heavy sectors. The effect of this nonquadratic approach is translated into nonlinear Regge trajectories with the generic form $M^2=a(n+b{)}^{\nu }$. We apply this sort of fits for the isovector states of $\omega$, $\varphi$, $J/\psi$, and $\mathrm{\Upsilon }$ mesons and compare with the corresponding holographic duals. We also extend these ideas to the heavy-light sector by using the isovector set of parameters to extrapolate the proper values of $\kappa$ and $\alpha$ through the average constituent mass $\overline{m}$ for each mesonic specie considered. In the same direction, we address the description of possible non-$q\overline{q}$ candidates using $\overline{m}$ as a holographic threshold, associated with the structure of the exotic state, to define the values of $\kappa$ and $\alpha$. We study the ${\pi }_1$ mesons in the light sector and the $Z_c$, $Y$, and $Z_b$ mesons in the heavy sector as possible exotic vector states. Finally, the RMS error for describing these twenty-seven states with fifteen parameters (four values for $\kappa$ and $\alpha$ respectively and seven values for $\overline{m}$) is 12.61%.

The condensate cosmology program of group field theory has produced several interesting results. The key idea is in the suggestion that a macroscopic homogeneous spacetime can be approximated by a dynamical condensate phase of the underlying microscopic system of an arbitrarily large number of candidate quanta of geometry. In this work, we extend the standard treatments in two ways: by using a class of thermal condensates, the coherent thermal states, which encode statistical fluctuations in quantum geometry; and by introducing a suitable class of smearing functions as nonsingular, well-behaved generalizations for relational clock frames in group field theory. In particular, we investigate an effective relational cosmological dynamics for homogeneous and isotropic spacetimes, extracted from a class of free group field theory models, and subsequently investigate aspects of its late and early times evolution. We find the correct classical limit of Friedmann equations at late times, with a bounce and an accelerated expansion at early times. Specifically, we find additional correction terms in the evolution equations corresponding to the statistical contribution of the new thermal condensates in general, and a higher upper bound on the number of $e$-folds, even without including any interactions.

We consider quasinormal modes and Hawking radiation of four-dimensional asymptotically flat black holes in the most general up to-cubic-order-in-curvature dimension-independent Einsteinian theory of gravity that shares its graviton spectrum with the Einstein theory on constant curvature backgrounds. We show that damping rate and real oscillation frequencies of quasinormal modes for scalar, electromagnetic and Dirac fields are suppressed once the coupling with the cubic term is on. The intensity of Hawking radiation is suppressed as well, leading to, roughly, one order longer lifetime at a sufficiently large coupling constant.

We find initial data for numerical relativity simulations of inhomogeneous cosmologies. This involves treating an exceptional case of the general relativity constraint equations. We devise analytic and numerical methods to treat this exceptional case. We apply the analytic method to the standard case of cosmology with a single scalar field. The numerical method is applied to the two-field ekpyrotic cosmology.

Cosmic inflation, which describes an accelerated expansion of the early Universe, yields the most successful predictions regarding temperature anisotropies in the cosmic microwave background (CMB). Nevertheless, the precise origin of the primordial perturbations and their quantum-to-classical transition is still an open issue. The continuous spontaneous localization model (CSL), in the cosmological context, might be used to provide a solution to the mentioned puzzles by considering an objective reduction of the inflaton wave function. In this work, we calculate the primordial power spectrum at the next leading order in the Hubble flow functions that results from applying the CSL model to slow roll inflation within the semiclassical gravity framework. We employ the method known as uniform approximation along with a second order expansion in the Hubble flow functions. We analyze some features in the CMB temperature and primordial power spectra that could help to distinguish between the standard prediction and our approach.

We calculate the average numbers of closed, flat, and open universes spontaneously created from nothing in the third quantization. The creation of universes is exponentially suppressed for large values of the kinetic energy of the inflaton, while for small kinetic energies, it is exponentially favored for closed universes over flat and open ones: for a scale of inflation less than about $2\times {10}^{16}\mathrm{GeV}$, the ratio of the number of closed universes to either the number of flat or open universes is $\frac{n_{\text{closed}}}{n_{\text{flat},\text{open}}}\gtrsim 10^{10^{10}}$.