In this work, we first perform a systematic study of the transition magnetic moments and the corresponding radiative decay behaviors of the $B_c$-like molecular states associated with their mass spectra, where the constituent quark model is adopted by considering the $S\text{−}D$ wave mixing effect. Our numerical results show that the radiative decay properties can be considered as the effective physical observable to reflect the inner structures of these $B_c$-like molecular states. Meanwhile, we also discuss the magnetic moments of the $B_c$-like molecular states, and we find that the magnetic moment properties can be used to distinguish the $B_c$-like molecular states from the conventional $B_c$ mesonic states, which have the same quantum numbers and similar masses. We expect that the present study can inspire the interest of the experimentalist in exploring the electromagnetic properties of the $B_c$-like molecular states, especially the radiative decay properties.

Correlations and fluctuations between produced particles in an ultrarelativistic nuclear collisions remain one of the key observables to understand the fundamentals of the particle production mechanism. More differential tools like forward-backward (FB) correlations between particles from two different phase spaces further strengthened our understanding. We study the strength of FB correlations in terms of charged-particle multiplicity and summed transverse momentum for proton-proton ($pp$) and proton-lead ($p\mathrm{Pb}$) collisions at center-of-mass energies $\sqrt{s}=13\mathrm{TeV}$ and $\sqrt{s_{\mathrm{NN}}}=5.02\mathrm{TeV}$, respectively, for the EPOS3 simulated events with hydrodynamical evolution of produced particles. Furthermore, the correlation strengths are separately obtained for the particles coming from the core and the corona. FB correlation strengths are examined as a function of the pseudorapidity gap (${\eta }_{\mathrm{gap}}$), pseudorapidity window width ($\delta \eta$), center-of-mass energy ($\sqrt{s}$), minimum transverse momentum ($p_{{\mathit{T}}_{\min }}$), and different multiplicity classes following standard kinematical cuts used by the ALICE and ATLAS experiments at the LHC for all three EPOS3 event samples. The EPOS3 model shows a similar trend of FB multiplicity and momentum correlation strengths for both $pp$ and $p\mathrm{Pb}$ systems, though the correlation strengths are found to be larger for the $p\mathrm{Pb}$ system than for the $pp$ system. Moreover, the $\delta \eta$-weighted average of FB correlation strengths as a function of different center-of-mass energies for $pp$ collisions delineates a tendency of saturation at very high energies.

We solve the full quasilinear kinetic equation governing nonresonant interactions of Alfvén waves with relativistic plasmas. This work was motivated by the need to determine the energy available for the synchrotron maser in the context of fast radio bursts (FRBs). This interaction can result in plasma heating and the formation of population inversions necessary for the maser. We find that population inversions containing $\sim 1\%–10\%$ of the distribution’s energy form in the relativistic regime, providing an explanation for the formation of the inversion in the environment expected near FRBs.

Classification of entanglement is an important problem in quantum resource theory. In this paper we discuss an embedding of this problem in the context of topological quantum field theories (TQFTs). This approach allows classifying entanglement patterns in terms of topological equivalence classes. In the bipartite case a classification equivalent to the one by stochastic local operations and classical communication (SLOCC) is constructed by restricting to a simple class of connectivity diagrams. Such diagrams characterize quantum states of TQFT up to braiding and tangling of the “connectome.” In the multipartite case the same restricted topological classification only captures a part of the SLOCC classes, in particular, it does not see the $W$ entanglement of three qubits. Nonlocal braiding of connections may solve the problem, but no finite classification is attempted in this case. Despite incompleteness, the connectome classification has a straightforward generalization to any number and dimension of parties and has a very intuitive interpretation, which might be useful for understanding specific properties of entanglement and for design of new quantum resources.

The two-body problem is extensively studied in open systems and asymptotically flat spacetimes. However, there are many systems where radiation is trapped: they range from radiating charges in cavities to low-energy excitations of massive degrees of freedom, to anti–de Sitter spacetimes. Here, we study the problem of motion of a pointlike scalar charge orbiting a massive compact object inside a cavity. We first show that—assuming circular motion—there are initial conditions for which the scalar self-force vanishes and the binary is eternal. We then consider the evolution of the system under radiation reaction in a toy model which we argue captures the essentials of orbiting particles. We show that eternal circular binaries may exist. We also show that the presence of cavity modes leads to chaos in regimes of strong coupling or when the system is initialized close enough to a resonance. Our results have implications for physics in anti–de Sitter spacetimes and possibly for binaries evolving within dark matter haloes, if it consists of massive fields.

We consider 4-dimensional spacetime manifolds that are piecewise Lorentzian, where the Lorentzian components of the manifold are separated by codimension-one planes (spacelike or timelike) on which the metric is degenerate. Such manifolds are of interest because they enlarge the smooth and nonsingular solution space of the Einstein equations. Planes of degeneracy that are perpendicular to each other can exist simultaneously. We describe various solutions of this type to the vacuum equations $G_{\mu \nu }=0$ and $G_{\mu \nu }+\mathrm{\Lambda }{g}_{\mu \nu }=0$, and to $G_{\mu \nu }=8\pi G{T}_{\mu \nu }$ for a perfect fluid. Novel examples include static gravitational lumps of finite curvature and a spacetime that responds to a cosmological constant via oscillations in time and/or space. A spacelike degeneracy plane can be used to avoid the big bang singularity, as we have further described elsewhere.

Motivated by a version of the “dipolar dark matter” model that aims at a relativistic completion of the phenomenology of MOND, we investigate the gravitational polarization mechanism in the canonical bimetric theory with an effective matter coupling. We explicitly show the fundamental obstacle why such theories cannot achieve a consistent gravitational polarization, and thus fail to recover the MONDian phenomenology at low energies.

Primordial black holes (PBHs) forming out of the collapse of enhanced cosmological perturbations provide access to the early Universe through their associated observational signatures. In particular, enhanced cosmological perturbations collapsing to form PBHs are responsible for the generation of a stochastic gravitational-wave background (SGWB) induced by second-order gravitational interactions, usually called scalar induced gravitational waves (SIGWs). This SGWB is sensitive to the underlying gravitational theory; hence it can be used as a novel tool to test the standard paradigm of gravity and constrain possible deviations from general relativity. In this work, we study the aforementioned GW signal within modified teleparallel gravity theories, developing a formalism for the derivation of the GW spectral abundance within any form of gravitational action. At the end, working within viable $f(T,\varphi )$ models without matter-gravity couplings, and accounting for the effect of monoparametric $f(T)$ gravity at the level of the source and the propagation of the tensor perturbations, we show that the respective GW signal is indistinguishable from that within GR. Interestingly, we find that in order to break the degeneracy between different $f(T)$ theories through the portal of SIGWs one should necessarily consider nonminimal matter-gravity couplings at the level of the gravitational action.

Scalar boson stars have attracted attention as simple models for exploring the nonlinear dynamics of a large class of ultracompact and black hole mimicking objects. Here, we study the impact of interactions in the scalar matter making up these stars. In particular, we show the pivotal role the scalar phase and vortex structure play during the late inspiral, merger, and postmerger oscillations of a binary boson star, as well as their impact on the properties of the merger remnant. To that end, we construct constraint satisfying binary boson star initial data and numerically evolve the nonlinear set of Einstein-Klein-Gordon equations. We demonstrate that the scalar interactions can significantly affect the inspiral gravitational wave amplitude and phase, and the length of a potential hypermassive phase shortly after merger. If a black hole is formed after merger, we find its spin angular momentum to be consistent with similar binary black hole and binary neutron star merger remnants. Furthermore, we formulate a mapping that approximately predicts the remnant properties of any given binary boson star merger. Guided by this mapping, we use numerical evolutions to explicitly demonstrate, for the first time, that rotating boson stars can form as remnants from the merger of two nonspinning boson stars. We characterize this new formation mechanism and discuss its robustness. Finally, we comment on the implications for rotating Proca stars.

We consider the consequences of a matter power spectrum which rises on small scales until eventually being cut off by microphysical processes associated with the particle nature of dark matter. Evolving the perturbations of a weakly interacting massive particle from before decoupling until deep in the nonlinear regime, we show that nonlinear structure can form abundantly at very high redshifts. In such a scenario, dark matter annihilation is substantially increased after matter-radiation equality. Furthermore, since the power spectrum can be increased over a broad range of scales, the first star forming halos may form earlier than usual as well. The next challenge is determining how early Universe observations may constrain such enhanced dark matter perturbations.

We use instant preheating as a mechanism to reheat the Universe when its evolution is modeled by a nonoscillating background. Once we obtain the reheating temperature, we calculate the number of $e$-folds using two different methods, which allows us to establish a relationship between the reheating temperature and the spectral index of scalar perturbations. We explore this connection to constrain the spectral index for different quintessential inflation models.

We present a minimal extension of the standard model that includes a long-lived fermion with weak-scale mass and an $\mathcal{O}(\mathrm{GeV})$ fermionic dark matter candidate both of which are coupled to quarks. Decays of a TeV-scale colored scalar in a radiation-dominated phase bring the former to a thermal abundance while also producing dark matter. The long-lived fermion then dominates the energy density of the Universe and drives a period of early matter domination. It decays to reheat the Universe, mainly through baryon-number-violating interactions that also generate a baryon asymmetry, with a small branching fraction to dark matter. We find the allowed parameter space of the model and show that it can be probed by proposed long-lived particle searches as well as next-generation neutron-antineutron oscillation experiments. This model provides a robust explanation of dark matter and baryogenesis as long as the Universe is in a radiation-dominated phase at $T\gtrsim \mathcal{O}(\mathrm{TeV})$.

The seesaw mechanism with three right-handed neutrinos has one as a well-motivated dark matter candidate if stable and the other two can explain baryon asymmetry via the thermal leptogenesis scenario. We explore the possibility of introducing additional particles to make the right-handed neutrino dark matter in thermal equilibrium and freeze out through a forbidden annihilation channel. Nowadays in the Universe, this forbidden channel can be reactivated by a strong gravitational potential such as the supermassive black hole in our galaxy center. The Fermi-LAT gamma ray data and dark matter relic density require this right-handed neutrino dark matter to have mass below 100 GeV and the existence of an additional boson $\varphi$ that can be tested at future lepton colliders.

We consider the propagation of fermions in the background of a scalar Bose-Einstein condensate. Some illustrative examples are discussed using simple Yukawa-type coupling models between the fermions and the scalar fields. The fermion dispersion relations are determined explicitly in those cases, to the lowest order, and in each case we discuss some of the properties of the propagating fermion modes. We also obtain the dispersion relations and wave functions of the scalar modes, which can be used to obtain the corrections (e.g., damping effects) to the fermion dispersion relations due to the interactions with the excitations of the Bose-Einstein condensate. Possible applications of these results in some contexts, such as neutrinos propagating in a scalar dark matter background, are mentioned.

Dense strongly interacting matter can exhibit regimes with spatial modulations, akin to crystalline phases. In this case particles can have a moat spectrum with minimal energy at nonzero momentum. We show that particle interferometry is a sensitive probe of such a regime in heavy-ion collisions. To this end, we develop a field-theoretical formalism that relates particle spectra to in-medium real-time correlation functions of quantum fields on curved hypersurfaces of spacetime. This is then applied to the study of Bose-Einstein correlations in a moat regime in heavy-ion collisions. The resulting two-particle spectra exhibit peaks at nonzero average pair momentum, in contrast to the two-particle spectra in a normal phase, which peak at zero momentum. These peaks lead to nontrivial structures in the ratio of two-particle correlation functions, which should be experimentally measurable if the resolution in the direction of average pair momentum is sufficiently large. We propose these structures in the correlation-function ratios as clear signature of a moat regime and spatially modulated phases in quantum chromodynamics (QCD).

Some time ago, we introduced a route to provide confinement in the sense that particle excitations would appear from condensates of fields that do not have physical asymptotic states [Phys. Rev. D 101, 094002 (2020)]. We envisaged this mechanism in an asymmetric vacuum phase of a complex gauge field theory. More recently, we showed how to define a Becchi-Rouet-Stora-Tyutin operator to the broken phase of a generic spontaneous broken field theory [Phys. Rev. D 105, 125007 (2022)]. Our intention here is to apply these late concepts to the previous complex field theory in order to give a cohomological characterization of those condensed states as actual physical observables of this theory in its broken phase.

We study the cosmology of a 3-brane in a specific five-dimensional scalar-gravity (i.e., soft-wall) background, known as the linear dilaton background. We discover that the Friedmann equation of the brane world automatically contains a term mimicking pressureless matter. We propose to identify this term as dark matter. This dark matter arises as a projection of the bulk black hole on the brane, which contributes to the brane Friedmann equation via both the Weyl tensor and the scalar stress tensor. The nontrivial matterlike behavior is due to an exact cancellation between the Weyl and scalar pressures. We show that the Newtonian potential receives only a mild short-distance correction going as inverse distance squared, ensuring compatibility of the linear dilaton brane world with observed 4D gravity. Our setup can be viewed as a consistent cosmological description of the holographic theories arising in the linear dilaton background. We also present more general scalar-gravity models where the brane cosmology features an effective energy density whose behavior smoothly interpolates between dark radiation, dark matter, and dark energy depending on a model parameter.

Neutral particles are notoriously difficult to observe through electromagnetic interactions. As a result, they naturally elude detection in most collider detectors. In this paper, we point out that neutral particles that interact through a dipole interaction can nevertheless be detected in far-forward detectors designed to search for long-lived particles (LLPs). In contrast to previous analyses that focused on neutral particles with elastic interactions, we consider inelastic interactions. This naturally leads to LLPs, and we demonstrate that FASER (and future experiments at the Forward Physics Facility) will be able to probe substantial regions of the associated parameter space. In particular, we find that FASER is capable of probing the region of parameter space wherein thermal freeze-out gives rise to an $\mathcal{O}(\mathrm{GeV})$ dark-matter candidate with the appropriate relic abundance, as well as regions of parameter space that are difficult to probe at fixed-target experiments. FASER and its successor experiments may therefore play a critical role in the discovery of such a dark-matter candidate.

We compute the spectra of flux tubes formed between a static quark-antiquark pair up to a significant number of excitations and for eight symmetries of the flux tubes, up to ${\mathrm{\Delta }}_u$, using pure SU(3) gauge lattice QCD in $3+1$ dimensions. To accomplish this goal, we use a large set of appropriate operators, an anisotropic tadpole improved action, smearing techniques, and solve a generalized eigenvalue problem. Moreover, we compare our results with the Nambu-Goto string model to evaluate possible tensions which could be a signal for novel phenomena. Especially, we provide evidence for the coupling of a massive particle, say, an axion, to the ${\mathrm{\Sigma }}_g^{-}$, ${\mathrm{\Sigma }}_u^{-}$, and ${\mathrm{\Sigma }}_u^{-*}$ flux tube with approximate masses $2.25\sqrt{\sigma }$, $1.85\sqrt{\sigma }$, and $3.30\sqrt{\sigma }$, respectively.

We compute the spectrum of the low-lying mesonic states with vector, scalar and pseudoscalar quantum numbers in QCD with one flavor. With three colors the fundamental and the two-index antisymmetric representations of the gauge group coincide. The latter is an orientifold theory that maps into the bosonic sector of $\mathcal{N}=1$ super Yang-Mills theory in the large number of colors limit. We employ Wilson fermions along with tree-level improvement in the gluonic and fermionic parts of the action. In this setup the Dirac operator can develop real negative eigenvalues. We therefore perform a detailed study in order to identify configurations where the fermion determinant is negative and eventually reweight them. We finally compare results with effective field theory predictions valid in the large $N_C$ limit and find reasonably consistent values despite $N_C$ being only three. Additionally, the spin-one sector provides a novel window for supersymmetric dynamics.