We study in this paper mechanisms of hadron melting based on the spectral representation of hadronic quantum channels, and examine the hadron-width dependence of the pressure. The findings are applied to a statistical hadron model of QCD thermodynamics, where hadron masses are distributed by the Hagedorn model and a uniform mechanism for producing hadron widths is assumed. According to this model the hadron–quark-gluon plasma transition occurs at $T\approx 200–250\mathrm{MeV}$, and the numerically observable $T_c=156\mathrm{MeV}$ crossover temperature is relevant for the onset of the hadron melting process.

All unitary irreducible representations of the centrally extended ($N$-odd) $N$-conformal Galilei group are constructed. The “on-shell” action of the group is derived and shown to coincide, in a special but most important case, with that obtained by Gomis and Kamimura [Phys. Rev. D 85, 045023 (2012)].

We extend the analysis of Chiba et al. [Phys. Rev. D 75, 124014 (2007)] of Solar System constraints on $f(R)$ gravity to a class of nonminimally coupled (NMC) theories of gravity. These generalize $f(R)$ theories by replacing the action functional of general relativity with a more general form involving two functions $f^1(R)$ and $f^2(R)$ of the Ricci scalar curvature $R$. While the function $f^1(R)$ is a nonlinear term in the action, analogous to $f(R)$ gravity, the function $f^2(R)$ yields a NMC between the matter Lagrangian density ${\mathcal{L}}_m$ and the scalar curvature. The developed method allows for obtaining constraints on the admissible classes of functions $f^1(R)$ and $f^2(R)$, by requiring that predictions of NMC gravity are compatible with Solar System tests of gravity. Then we consider a NMC model which accounts for the observed accelerated expansion of the Universe and we show that such a model cannot be constrained by the present method.

The dynamics of the Brans-Dicke theory with a scalar field potential function is investigated. We show that the system with a barotropic matter content can be reduced to an autonomous three-dimensional dynamical system. For an arbitrary potential function, we found the values of the Brans-Dicke parameter for which a global attractor in the phase space representing the de Sitter state exists. Using linearized solutions in the vicinity of this critical point, we show that the evolution of the Universe mimics the $\Lambda \mathrm{CDM}$ model. From the recent Planck satellite data, we obtain constraints on the variability of the effective gravitational coupling constant as well as the lower limit of the mass of the Brans-Dicke scalar field at the de Sitter state.

We present the first direct comparison of numerical simulations of neutron star-black hole and black hole-black hole mergers in full general relativity. We focus on a configuration with nonspinning objects and within the most likely range of mass ratio for neutron star-black hole systems ($q=6$). In this region of the parameter space, the neutron star is not tidally disrupted prior to merger, and we show that the two types of mergers appear remarkably similar. The effect of the presence of a neutron star on the gravitational wave signal is not only undetectable by the next generation of gravitational wave detectors, but also too small to be measured in the numerical simulations: even the plunge, merger and ringdown signals appear in perfect agreement for both types of binaries. The characteristics of the post-merger remnants are equally similar, with the masses of the final black holes agreeing within $\delta M_{\mathrm{BH}}<5\times {10}^{-4}{M}_{\mathrm{BH}}$ and their dimensionless spins within $\delta {\chi }_{\mathrm{BH}}<{10}^{-3}$. The rate of periastron advance in the mixed binary agrees with previously published binary black hole results, and we use the inspiral waveforms to place constraints on the accuracy of our numerical simulations independent of algorithmic choices made for each type of binary. Overall, our results indicate that nondisrupting neutron star-black hole mergers are exceptionally well modeled by black hole-black hole mergers, and that given the absence of mass ejection, accretion disk formation, or differences in the gravitational wave signals, only electromagnetic precursors could prove the presence of a neutron star in low-spin systems of total mass $\sim 10M_{\odot }$, at least until the advent of gravitational wave detectors with a sensitivity comparable to that of the proposed Einstein Telescope.

Motivated by a recent proposal (by Koslowski-Sahlmann) of a kinematical representation in loop quantum gravity (LQG) with a nondegenerate vacuum metric, we construct a polymer quantization of the parametrized massless scalar field theory on a Minkowskian cylinder. The diffeomorphism covariant kinematics is based on states that carry a continuous label corresponding to smooth embedding geometries, in addition to the discrete embedding and matter labels. The physical state space, obtained through the group averaging procedure, is nonseparable. A physical state in this theory can be interpreted as a quantum spacetime, which is composed of discrete strips and supersedes the classical continuum. We find that the conformal group is broken in the quantum theory and consists of all Poincaré translations. These features are remarkably different compared to the case without a smooth embedding. Finally, we analyze the length operator whose spectrum is shown to be a sum of contributions from the continuous and discrete embedding geometries, being in perfect analogy with the spectra of geometrical operators in LQG with a nondegenerate vacuum geometry.

We study the impact of primordial non-Gaussianity on the density profile of dark matter halos by using the semianalytical model introduced recently by Dalal et al. which relates the peaks of the initial linear density field to the final density profile of dark matter halos. Models with primordial non-Gaussianity typically produce an initial density field that differs from that produced in Gaussian models. We use the path-integral formulation of excursion set theory to calculate the non-Gaussian corrections to the peak profile and derive the statistics of the peaks of the non-Gaussian density field. In the context of the semianalytic model for halo profiles, currently allowed values for primordial non-Gaussianity would increase the shapes of the inner dark matter profiles, but only at the sub-percent level except in the very innermost regions.

We present the implementation of a fast estimator for the full dark matter bispectrum of a three-dimensional (3D) particle distribution relying on a separable modal expansion of the bispectrum. The computational cost of accurate bispectrum estimation is negligible relative to simulation evolution, so the isotropic bispectrum can be used as a standard diagnostic whenever the power spectrum is evaluated. As an application, we measure the evolution of gravitational and primordial dark matter bispectra in $N$-body simulations with Gaussian and non-Gaussian initial conditions of the local, equilateral, orthogonal and flattened shape. The results are compared to theoretical models using a 3D visualization, 3D shape correlations and the cumulative bispectrum signal-to-noise, all of which can be evaluated extremely quickly. Our measured bispectra are determined by $\mathcal{O}(50)$ coefficients, which can be used as fitting formulas in the nonlinear regime and for non-Gaussian initial conditions. In the nonlinear regime with $k<2h{\mathrm{Mpc}}^{-1}$, we find an excellent correlation between the measured dark matter bispectrum and a simple model based on a “constant” bispectrum plus a (nonlinear) tree-level gravitational bispectrum. In the same range for non-Gaussian simulations, we find the measured excess bispectrum (i.e. the difference with the measured gravitational bispectrum) has an excellent correlation with a phenomenological model consisting of the constant bispectrum plus a (nonlinear) tree-level primordial bispectrum. We demonstrate that the constant contribution to the non-Gaussian bispectrum can be understood as a time-shift of the constant mode in the gravitational bispectrum, which is motivated by the one-halo model. The final amplitude of this extra non-Gaussian constant contribution is directly related to the initial amplitude of the constant mode in the primordial bispectrum. We also comment on the effects of regular grid and glass initial conditions on the bispectrum.

The dark matter annihilation rate at small relative velocities can be amplified by a large boost factor using various mechanisms, including Sommerfeld enhancement, resonance enhancement, and Breit-Wigner enhancement. These mechanisms all involve a resonance near the threshold for a pair of dark matter particles. We point out that if the resonance is in the $S$-wave channel, the mechanisms are equivalent sufficiently near the resonance and they are constrained by universal two-body physics. The amplified annihilation rate requires a corresponding amplification of the elastic scattering cross section. If the resonance is a bound state below the threshold, it has an increased lifetime that is inversely proportional to the square root of the binding energy. Its spatial structure is that of two dark matter particles whose mean separation is also inversely proportional to the square root of the binding energy.

Monojet searches are a powerful way to place model-independent constraints on effective operators coupling dark matter to the standard model. For operators generated by the exchange of a scalar mediator, however, couplings to light quarks are suppressed and the prospect of probing such interactions through the inclusive monojet channel at the LHC is limited. We propose dedicated searches, focusing on bottom and top quark final states, to constrain this class of operators. We show that a search in mono $b$-jets can significantly improve current limits. The mono-$b$ signal arises partly from direct production of $b$ quarks in association with dark matter, but the dominant component is from top quark pair production in the kinematic regime where one top is boosted. A search for tops plus missing energy can strengthen the bounds even more; in this case signal and background have very different missing energy distributions. We find an overall improvement by several orders of magnitude in the bound on the direct detection cross section for scalar or pseudoscalar couplings.

We consider two flavor magnetized quark matter in the presence of a repulsive vector coupling ($G_V$) devoting special attention to the low temperature region of the phase diagram to show how this type of interaction counterbalances the effects produced by a strong magnetic field. The most important effects occur at intermediate and low temperatures affecting the location of the critical end point as well as the region of first order chiral transitions. When $G_V=0$ the presence of high magnetic fields ($eB\ge 10m_{\pi }^2$) increases the density coexistence region with respect to the case when $B$ and $G_V$ are absent while a decrease of this region is observed at high $G_V$ values and vanishing magnetic fields. Another interesting aspect observed at the low temperature region is that the usual decrease of the coexistence chemical value (inverse magnetic catalysis) at $G_V=0$ is highly affected by the presence of the vector interaction which acts in the opposite way. Our investigation also shows that the presence of a repulsive vector interaction enhances the de Haas-van Alphen oscillations which, for very low temperatures, take place at $eB\lesssim 6m_{\pi }^2$. We observe that the presence of a magnetic field, together with a repulsive vector interaction, gives rise to a complex transition pattern since $B$ favors the appearance of multiple solutions to the gap equation whereas $G_V$ turns some metastable solutions into stable ones allowing for a cascade of transitions to occur.

We study the impact that a heavy generation of vectorlike leptons can have on the value of the electric dipole moment of the electron, and the rates for the flavor violating processes $\mu \to e\gamma$ and $\mu \to 3e$. The smallness of the charged lepton masses suggests that at least some of the Yukawa coupling constants of the vectorlike leptons to the ordinary leptons or amongst themselves are small, but even with such small couplings experiments trying to detect these quantities are sensitive to extra generation lepton masses up to about 100 TeV.

Assuming that the 125 GeV particle observed at the LHC is a composite scalar and responsible for the electroweak gauge symmetry breaking, we consider the possibility that the bound state is generated by a non-Abelian gauge theory with dynamically generated gauge boson masses and a specific chiral symmetry breaking dynamics motivated by confinement. The scalar mass is computed with the use of the Bethe-Salpeter equation and its normalization condition as a function of the $SU(N)$ group and the respective fermionic representation. If the fermions that form the composite state are in the fundamental representation of the $SU(N)$ group, we can generate such a light boson only for one specific number of fermions for each group. We address the uncertainties underlying this result, when considering the strong dynamics in isolation.

We calculate the intrinsic strangeness of the nucleon, $⟨N|\overline{s}s|N⟩-⟨0|\overline{s}s|0⟩$, using the MILC library of improved staggered gauge configurations using the Asqtad and HISQ actions. Additionally, we present a preliminary calculation of the intrinsic charm of the nucleon using the HISQ action with dynamical charm. The calculation is done with a method which incorporates features of both commonly used methods, the direct evaluation of the three-point function and the application of the Feynman-Hellman theorem. We present an improvement on this method that further reduces the statistical error, and check the result from this hybrid method against the other two methods and find that they are consistent. The values for $⟨N|\overline{s}s|N⟩$ and $⟨N|\overline{c}c|N⟩$ found here, together with perturbative results for heavy quarks, show that dark matter scattering through Higgs-like exchange receives roughly equal contributions from all heavy quark flavors.

We explore the consequences of heavy flavor, heavy quark spin, and heavy antiquark-diquark symmetries for hadronic molecules within an effective field theory framework. Owing to heavy antiquark-diquark symmetry, the doubly heavy baryons have approximately the same light-quark structure as the heavy antimesons. As a consequence, the existence of a heavy meson-antimeson molecule implies the possibility of a partner composed of a heavy meson and a doubly heavy baryon. In this regard, the $D{\overline{D}}^{*}$ molecular nature of the $X(3872)$ will hint at the existence of several baryonic partners with isospin $I=0$ and $J^P=\frac{5}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{}$ or $\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{}$. Moreover, if the $Z_b(10650)$ turns out to be a $B^{*}{\overline{B}}^{*}$ bound state, we can be confident of the existence of ${\Xi }_{bb}^{*}{\overline{B}}^{*}$ hadronic molecules with quantum numbers $I(J^P)=1(\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{})$ and $I(J^P)=1(\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{})$. These states are of special interest since they can be considered to be triply heavy pentaquarks.

The cross section for the process $e^{+}{e}^{-}\to \omega {\pi }^0\to {\pi }^0{\pi }^0\gamma$ has been measured in the center-of-mass energy range 1.05–2.00 GeV. The experiment has been performed at the $e^{+}{e}^{-}$ collider VEPP-2000 with the SND detector. The measured $e^{+}{e}^{-}\to \omega {\pi }^0$ cross section above 1.4 GeV is the most accurate to date. Below 1.4 GeV our data are in good agreement with the previous SND and CMD-2 measurements. Data on the $e^{+}{e}^{-}\to \omega {\pi }^0$ cross section are well described by the vector meson dominance model with two excited $\rho$-like states. From the measured cross section we have extracted the ${\gamma }^{*}\to \omega {\pi }^0$ transition form factor. It has been found that the vector meson dominance model cannot describe simultaneously our data and data obtained from the $\omega \to {\pi }^0{\mu }^{+}{\mu }^{-}$ decay. We have also tested the conserved vector current hypothesis comparing our results on the $e^{+}{e}^{-}\to \omega {\pi }^0$ cross section with data on the ${\tau }^{-}\to \omega {\pi }^{-}{\nu }_{\tau }$ decay and have found that the conserved vector current hypothesis works well within the reached experimental accuracy of about 5%.

We investigate the photoproduction of $K^{*0}{\Sigma }^{+}$ and $K^{*+}{\Sigma }^0$ off the proton target, employing the effective Lagrangian approach at the tree-level Born approximation. In addition to the $(s,t,u)$-channel Born diagrams, we take into account various baryon-resonance contributions such as $D_{13}(2080)$, $S_{11}(2090)$, $G_{17}(2190)$, $D_{15}(2200)$, $S_{31}(2150)$, $G_{37}(2200)$, $F_{37}(2390)$, and ${\Sigma }^{*}(1385,3/2^{+})$ in a fully covariant manner. We present the numerical results for the energy and angular dependences for the cross sections in comparison to available experimental data. The single-polarization observables, i.e., the photon-beam (${\Sigma }_{\gamma }$), recoil ($P_y$), and target ($T_y$) baryon polarization asymmetries are computed as well for future experiments. We observe from the numerical results that the resonance contributions play a minor role in producing the strength of the cross sections, being different from the $K^{*}\Lambda$ photoproduction. In contrast, it turns out that the $\Delta (1232)$-pole contribution and $K$ exchange in the $t$ channel dominate the scattering process. On the other hand, the higher resonances influence the polarization observables such as the recoil and target asymmetries.

We analyze the subleading nonresonant contributions to the $e^{+}{e}^{-}\to W^{+}{W}^{-}b\overline{b}$ cross section at energies near the top-antitop threshold. These correspond to next-to-next-to-leading-order (NNLO) corrections with respect to the leading-order resonant result. We show that these corrections produce $1/ϵ$ endpoint singularities which precisely cancel the finite-width divergences arising in the resonant production of the $W^{+}{W}^{-}b\overline{b}$ final state from on-shell decays of the top and antitop quarks at the same order. We also provide analytic results for the $(m_t/\Lambda {)}^2$, ($m_t/\Lambda$) and $(m_t/\Lambda {)}^0\log \Lambda$ terms that dominate the expansion in powers of ($\Lambda /m_t$) of the complete set of NNLO nonresonant corrections, where $\Lambda$ is a cut imposed on the invariant masses of the $bW$ pairs that is neither too tight nor too loose ($m_t{\Gamma }_t\ll {\Lambda }^2\ll m_t^2$).

We study the multiple scattering effects on inclusive particle production in $\mathrm{p}+\mathrm{A}$ and $\gamma +\mathrm{A}$ collisions. Specifically, we concentrate on the region where the parton momentum fraction in the nucleus $x\sim \mathcal{O}(1)$ and incoherent multiple interactions are relevant. By taking into account both initial-state and final-state double scattering, we derive the nuclear size-enhanced power corrections to the differential cross section for single inclusive hadron production in $\mathrm{p}+\mathrm{A}$ and $\gamma +\mathrm{A}$ reactions, and for prompt photon production in $\mathrm{p}+\mathrm{A}$ reactions. We find that the final result can be written in a simple compact form in terms of four-parton correlation functions, in which the second-derivative, first-derivative and nonderivative terms of the correlation distributions share the same hard-scattering functions. We expect our result to be especially relevant for understanding the nuclear modification of particle production in the backward rapidity regions in $\mathrm{p}+\mathrm{A}$ and $\mathrm{e}+\mathrm{A}$ collisions.