We propose that the Higgs phase of a gauge Higgs theory is the phase of spontaneously broken custodial symmetry, and we present a new gauge invariant order parameter for custodial symmetry breaking which is very closely analogous to the Edwards-Anderson order parameter for spin glasses. Custodial symmetry is a global symmetry acting on the Higgs field alone, and we show here that the spin glass transition in gauge Higgs theories, from a QCD-like phase to a Higgs phase of broken custodial symmetry, coincides with the transition between two distinct types of confinement. These are color confinement in the Higgs phase and a stronger version of confinement, which we have termed “separation of charge” confinement, in the QCD-like phase.

We numerically study the single-flavor Schwinger model with a topological $\theta$-term, which is practically inaccessible by standard lattice Monte Carlo simulations due to the sign problem. By using numerical methods based on tensor networks, especially the one-dimensional matrix product states, we explore the nontrivial $\theta$-dependence of several lattice and continuum quantities in the Hamiltonian formulation. In particular, we compute the ground-state energy, the electric field, the chiral fermion condensate, and the topological vacuum susceptibility for positive, zero, and even negative fermion mass. In the chiral limit, we demonstrate that the continuum model becomes independent of the vacuum angle $\theta$, thus respecting $CP$ invariance, while lattice artifacts still depend on $\theta$. We also confirm that negative masses can be mapped to positive masses by shifting $\theta \to \theta +\pi$ due to the axial anomaly in the continuum, while lattice artifacts nontrivially distort this mapping. This mass regime is particularly interesting for the ($3+1$)-dimensional QCD analog of the Schwinger model, the sign problem of which requires the development and testing of new numerical techniques beyond the conventional Monte Carlo approach.

We study the light quark-mass dependence of charmed baryon masses as measured by various QCD lattice collaborations. A global fit to such data based on the chiral SU(3) Lagrangian is reported on. All low-energy constants that are relevant at next-to-next-to-next-to-leading order are determined from the lattice datasets where constraints from sum rules as they follow from large-$N_c$ QCD at subleading order are considered. The expected hierarchy for the low-energy constants in the $1/N_c$ expansion is confirmed by our global fits to the lattice data. With our results, the low-energy interaction of the Goldstone bosons with the charmed baryon ground states is well constrained and the path toward realistic coupled-channel computations in this sector of QCD is prepared.

Baryon chiral perturbation theory (BChPT) combined with the $1/N_c$ expansion is applied to the $SU(3)$ vector currents. In terms of the $\xi$ power counting linking the low-energy and $1/N_c$ expansions according to $\mathcal{O}(\xi )=\mathcal{O}(p)=\mathcal{O}(1/N_c)$, the study is carried out to next-to-next-to-leading order, and it includes $SU(3)$ breaking corrections to the $|\mathrm{\Delta }S|=1$ vector charges, charge radii, and magnetic moments and radii. The results are obtained for generic $N_c$, allowing for investigating the various scalings in $N_c$.

We explore the effect of including quantum fluctuations in the two flavor Nambu–Jona-Lasinio model at finite temperature. This is accomplished, in a symmetry preserving way, by including collective and noncollective modes in the one-meson-loop gap equation which originate from poles and branch cuts in the complex plane, respectively. The inclusion of a boson cutoff, ${\mathrm{\Lambda }}_b$, is necessary to regularize the meson-loop momenta. This new parameter is used to study the influence of going beyond the usual mean field approximation in the quark condensate. As the temperature increases, chiral symmetry tends to get restored, the collective modes melt and only noncollective modes contribute to the quark condensate. With the inclusion of such modes, the quark condensate at finite temperature has a different behavior than at mean field level that will be explored.

The calculation of the decay $X(3872)\to D^0{\overline{D}}^0{\pi }^0$ in effective field theory is revisited to include final state ${\pi }^0{D}^0$, ${\pi }^0{\overline{D}}^0$ and $D^0{\overline{D}}^0$ rescattering diagrams. These introduce significant uncertainty into the prediction for the partial width as a function of the binding energy. The differential distribution in the pion energy is also studied for the first time. The normalization of the distribution is again quite uncertain due to higher order effects but the shape of the distribution is unaffected by higher order corrections. Furthermore the shape of the distribution and the location of the peak are sensitive to the binding energy of $X(3872)$. The shape is strongly impacted by the presence of virtual $D^{*0}$ graphs which highlights the molecular nature of the $X(3872)$. Measurement of the pion energy distribution in the decay $X(3872)\to D^0{\overline{D}}^0{\pi }^0$ can reveal interesting information about the binding nature of the $X(3872)$.

High-multiplicity $pp$ collisions exhibit features, traditionally associated with nuclear effects. Coherence motivates to treat high-multiplicity $pp$, $pA$, and $AA$ collisions on an equal footing. We rely on the phenomenological parametrization for mean multiplicities of light hadrons and $J/\psi$, assuming their linear dependence on $N_{coll}$ in $pA$ collisions. The results of this approach underestimate the recently measured production rate of $J/\psi$ at very high hadronic multiplicities. The linear dependence of $J/\psi$ multiplicity on $N_{coll}$ is subject to predicted nonlinear corrections, related to mutual boosting of the saturation scales in colliding dense parton clouds. A parameter-free calculation of the nonlinear corrections allows us to explain data for $p_T$-integrated yield of $J/\psi$ at high hadronic multiplicities. Calculations are in a good accord with data binned in several $p_T$ intervals as well. As was predicted, $\mathrm{\Upsilon }$ and $J/\psi$ are equally suppressed at forward rapidities in $pA$ collisions. Consequently, their fractional multiplicities at forward rapidities in $pp$ collisions are equal as well, and their magnitude agrees with data.

In this work, we present a bag-type model within a nonextensive statistics applied to the description of the properties of a hadronic system with an underlying fractal structure. The nonextensive ideal gas inside the bag is determined by the grand canonical partition function from which pressure, energy, and particle density, as well as temperature and chemical potential are obtained for the hadronic system. These quantities are studied in the approximation of fixed mass for all bag constituents but also for discrete and continuum masses. In all cases, the freeze-out line, corresponding to the energy per particle equal to 1 GeV, and the lines corresponding to a fractal structure inside the proton volume are obtained. Finally, the pressure on the bag surface of the proton is calculated and the resulting value $(0.135\mathrm{GeV}{)}^4$ is obtained.

We demonstrate that the classification of boosted, hadronically decaying, weak gauge bosons can be significantly improved over traditional cut-based and boosted decision tree-based methods using deep learning and the jet charge variable. We construct binary taggers for $W^{+}$ vs $W^{-}$ and $Z$ vs $W$ discrimination, as well as an overall ternary classifier for $W^{+}/W^{-}/Z$ discrimination. Besides a simple convolutional neural network, we also explore a composite of two simple convolutional neural networks, with different numbers of layers in the jet $p_T$ and jet charge channels. We find that this novel structure boosts the performance particularly when considering the $Z$ boson as a signal. The methods presented here can enhance the physics potential in Standard Model measurements and searches for new physics that are sensitive to the electric charge of weak gauge bosons.

We present an analysis of electron recoils in cryogenic germanium detectors operated during the SuperCDMS Soudan experiment. The data are used to set new constraints on the axioelectric coupling of axionlike particles and the kinetic mixing parameter of dark photons, assuming the respective species constitutes all of the galactic dark matter. This study covers the mass range from $40\mathrm{eV}/c^2$ to $500\mathrm{keV}/c^2$ for both candidates, excluding previously untested parameter space for masses below $\sim 1\mathrm{keV}/c^2$. For the kinetic mixing of dark photons, values below ${10}^{-15}$ are reached for particle masses around $100\mathrm{eV}/c^2$; for the axioelectric coupling of axionlike particles, values below ${10}^{-12}$ are reached for particles with masses in the range of a few-hundred $\mathrm{eV}/c^2$.

Jet substructure quantities are measured using jets groomed with the soft-drop grooming procedure in dijet events from $32.9{\mathrm{fb}}^{-1}$ of $pp$ collisions collected with the ATLAS detector at $\sqrt{s}=13\mathrm{TeV}$. These observables are sensitive to a wide range of QCD phenomena. Some observables, such as the jet mass and opening angle between the two subjets which pass the soft-drop condition, can be described by a high-order (resummed) series in the strong coupling constant ${\alpha }_{\mathrm{S}}$. Other observables, such as the momentum sharing between the two subjets, are nearly independent of ${\alpha }_{\mathrm{S}}$. These observables can be constructed using all interacting particles or using only charged particles reconstructed in the inner tracking detectors. Track-based versions of these observables are not collinear safe, but are measured more precisely, and universal nonperturbative functions can absorb the collinear singularities. The unfolded data are directly compared with QCD calculations and hadron-level Monte Carlo simulations. The measurements are performed in different pseudorapidity regions, which are then used to extract quark and gluon jet shapes using the predicted quark and gluon fractions in each region. All of the parton shower and analytical calculations provide an excellent description of the data in most regions of phase space.

Axions, the hypothetical particles restoring the charge-parity symmetry in the strong sector of the Standard Model and one of the most prone candidates for dark matter, are well known to interact with plasmas. In a recent publication [Phys. Rev. Lett. 120, 181803 (2018)], we show that if the plasma dynamically responds to the presence of axions, then a new quasiparticle (the axion-plasmon polariton) can be formed, being at the basis of a new generation of plasma-based detection techniques. In this work, we exploit the axion-plasmon hybridization to actively produce axions in streaming magnetized plasmas. The produced axions can then be detected by reconversion into photons in a scheme that is similar to the light-shining-through-a-wall experiments.

We explore, in the framework of linearized quantum gravity, the induced gravitational interaction between two gravitationally polarizable objects in their ground states in the presence of an external quantized gravitational radiation field. The interaction energy decreases as $r^{-5}$ in the near regime, and oscillates with a decreasing amplitude proportional to $r^{-1}$ in the far regime, where $r$ is the distance between the two objects. The interaction can be either attractive or repulsive depending on the propagation direction, polarization and frequency of the external gravitational field. That is, the induced interaction can be manipulated by varying the relative direction between the orientation of the objects with respect to the propagation direction of the incident gravitational radiation.

In this work, we consider a Casimir apparatus that is put into free fall (e.g., falling into a black hole). Working in $1+1\mathrm{D}$, we find that two main effects occur: First, the Casimir energy density experiences a tidal effect where negative energy is pushed toward the plates and the resulting force experienced by the plates is increased. Second, the process of falling is inherently nonequilibrium and we treat it as such, demonstrating that the Casimir energy density moves back and forth between the plates after being “dropped,” with the force modulating in synchrony. In this way, the Casimir energy behaves as a classical liquid might, putting (negative) pressure on the walls as it moves about in its container. In particular, we consider this in the context of a black hole and the multiple vacua that can be achieved outside of the apparatus.

We consider scattering of Faddeev-Kulish electrons in QED and study the entanglement between the hard and soft particles in the final state at the perturbative level. The soft photon spectrum naturally splits into two parts: (i) soft photons with energies less than a characteristic infrared scale $E_d$ present in the clouds accompanying the asymptotic charged particles, and (ii) sufficiently low energy photons with energies greater than $E_d$, comprising the soft part of the emitted radiation. We construct the density matrix associated with tracing over the radiative soft photons and calculate the entanglement entropy perturbatively. We find that the entanglement entropy is free of any infrared divergences order by order in perturbation theory. On the other hand, infrared divergences in the perturbative expansion for the entanglement entropy appear upon tracing over the entire spectrum of soft photons, including those in the clouds. To leading order the entanglement entropy is set by the square of the Fock basis amplitude for real single soft photon emission, which leads to a logarithmic infrared divergence when integrated over the photon momentum. We argue that the infrared divergences in the entanglement entropy (per particle flux per unit time) in this latter case persist to all orders in perturbation theory in the infinite volume limit.

Twenty-two years ago, Rebhan and van Nieuwenhuizen showed that loop corrections to the mass of a quantum soliton depend on a choice of matching condition for the regulators of the vacuum and one-soliton sector Hamiltonians. In supersymmetric theories, regulators which preserve supersymmetry yield the correct quantum corrections, as these are dictated by supersymmetry. However, in a general theory. it is not known which matching condition yields the correct mass. We use the leading term in the operator that creates the soliton to construct the regulated one-soliton sector Hamiltonian from that of the vacuum sector, providing the correct matching condition. As an application, we derive a simple formula for the one-loop mass of a kink in a large class of ($1+1$)-dimensional scalar field theories, and also, at one loop, we diagonalize the Hamiltonian which describes the kink excitations.

The parametrized black hole quasinormal ringdown formalism is useful to compute quasinormal mode (QNM) frequencies if a master equation for the gravitational perturbation around a black hole has a small deviation from the Regge-Wheeler or Zerilli equation. In this formalism, the deviation of QNM frequency from general relativity can be calculated by small deviation parameters and model independent coefficients. In this paper, we derive recursion relations for the model independent coefficients. Using these relations, the higher order coefficients are written only by the lower order coefficients. Thus, we only need the lower order coefficients when we numerically compute the model independent coefficients.

In a previous paper, one of us calculated iron $\mathrm{K}\alpha$ line profiles emitted from possible accretion disks around traversable wormholes as a first step to use x-ray reflection spectroscopy to search for astrophysical wormholes in active galactic nuclei. In the present paper, we extend that work and construct an XSPEC model for the whole relativistic reflection spectrum. We apply our model to XMM-Newton and NuSTAR observations of the supermassive object in MCG-6-30-15 and we check whether these observations prefer the hypothesis that the central body is a Kerr black hole or a traversable wormhole. We find that the two models provide equally good fits, so with the available data we cannot distinguish the black hole and wormhole scenarios.

The big bang singularity of the expanding-universe Friedmann solution of the Einstein gravitational field equation can be regularized by the introduction of a degenerate metric and a nonzero length scale $b$. The result is a nonsingular bounce of the cosmic scale factor with a contracting prebounce phase and an expanding postbounce phase. The corresponding maximum values of the curvature and the energy density occur at the moment of the bounce and are proportional to powers of $1/b$. This article presents a detailed calculation of the dynamics of such a nonsingular bounce. In addition, a comparison is made between this nonsingular bounce and the bounces of loop quantum cosmology and string cosmology.