We discuss the obstruction to the construction of a multiparticle field theory on a $\kappa$-Minkowski noncommutative spacetime: the existence of multilocal functions which respect the deformed symmetries of the problem. This construction is only possible for a lightlike version of the commutation relations, if one requires invariance of the tensor product algebra under the coaction of the $\kappa$-Poincaré group. This necessitates a braided tensor product. We study the representations of this product, and prove that $\kappa$-Poincaré-invariant $N$-point functions belong to an Abelian subalgebra, and are therefore commutative. We use this construction to define the 2-point Whightman and Pauli–Jordan functions, which turn out to be identical to the undeformed ones. We finally outline how to construct a free scalar $\kappa$-Poincaré-invariant quantum field theory, and identify some open problems.

We study the relations of the positive frequency mode functions of Dirac field in 4-dimensional Minkowski spacetime covered with Rindler and Kasner coordinates, and describe the explicit form of the Minkowski vacuum state with the quantum states in Kasner and Rindler regions, and analytically continue the solutions. As a result, we obtain the correspondence of the positive frequency mode functions in Kasner region and Rindler region in a unified manner which derives vacuum entanglement.

Nonminimally coupled curvature-matter gravity models are an interesting alternative to the theory of general relativity to address the dark energy and dark matter cosmological problems. These models have complex field equations that prevent a full analytical study. Nonetheless, in a particular limit, the behavior of a matter distribution can, in these models, be described by a Schrödinger-Newton system. In nonlinear optics, the Schrödinger-Newton system can be used to tackle a wide variety of relevant situations, and several numerical tools have been developed for this purpose. Interestingly, these methods can be adapted to study general relativity problems as well as its extensions. In this work, we report the use of these numerical tools to study a particular nonminimal coupling model that introduces two new potentials, an attractive Yukawa potential, and a repulsive potential proportional to the energy density. Using the imaginary-time propagation method, we have shown that static solutions arise even at low energy density regimes.

We investigate the linear dynamics of an electromagnetic field propagating in curved spacetime in the presence of plasma. The dynamical equations are generically more involved and richer than the effective Proca equation adopted as a model in previous work. We discuss the general equations and focus on the case of a cold plasma in the background of a spherically symmetric black hole, showing that the system admits plasma-driven, quasibound electromagnetic states that are prone to become superradiantly unstable when the black hole rotates. The quasibound states are different from those of the Proca equation and have some similarities with the case of a massive scalar field, suggesting that the linear instability can be strongly suppressed compared to previous estimates. Our framework provides the first step toward a full understanding of the plasma-photon interactions around astrophysical black holes.

Gravitational spectroscopy—the measurement of the quasi-normal modes of a black hole from the ringdown signal of a binary black hole coalescence—is one of the most promising tools to test gravity in the strong-field, large-curvature regime, but without the knowledge of the black hole quasinormal modes in specific cases of modified gravity theories, only null tests of general relativity are possible. More specifically, we need to know the modes of rotating black holes, because typical compact binary mergers lead to black holes with large spins. In this article we compute, for the first time, the gravitational quasinormal modes of rotating black holes in a modified gravity theory, up to first order in the spin. We consider Einstein-dilaton Gauss-Bonnet gravity, one of the simplest modifications of general relativity in the large-curvature regime. We find that the shifts in the mode frequencies and damping times due to general relativity modifications are significantly magnified by rotation.

The instant preheating mechanism in the framework of a scale invariant two measures theory is studied. We introduce this mechanism into a nonoscillating inflationary model as another possible solution to the reheating of the Universe in this theory. In this framework, we consider that the model includes two scalar matter fields, the first is a dilaton field that transforms under scale transformations and will be considered also as the field that drives inflation, and the second is a scalar field that will interact with the inflaton through an effective potential. By assuming this interaction term, we obtain a scenario of instant radiation or decay of particles according to the domain the effective mass of the field that interacts with the inflaton. Also, we consider a scale invariant Yukawa interaction. After performing the transition to the physical Einstein frame, we obtain an expression for the decay rate from our scalar field going into two fermions. Besides, from specific decay rates, different constraints and bounds for the coupling parameters associated with our model are found.

We present a minimal approach to the generation of the baryon ($B$) asymmetry of the Universe, in which the asymmetry is generated in a complex inflaton condensate via $B$-violating quadratic inflaton potential terms and the Affleck-Dine mechanism. We show that the $B$-violating quadratic mass terms create an oscillating asymmetry in the complex inflaton condensate at late times. The final asymmetry transferred to the Standard Model sector at reheating is naturally reduced to the magnitude of the observed $B$ asymmetry by the effect of averaging over the $B$ oscillations. This approach to baryogenesis can easily be realized in a wide range of inflation models.

We develop a novel technique for numerically computing the primordial power spectra of comoving curvature perturbations. By finding suitable analytic approximations for different regions of the mode equations and stitching them together, we reduce the solution of a differential equation to repeated matrix multiplication. This results in a wave-number-dependent increase in speed which is orders of magnitude faster than traditional approaches at intermediate and large wave numbers. We demonstrate the method’s efficacy on the challenging case of a stepped quadratic potential with kinetic dominance. We further generalize to a novel class of frozen initial conditions which prove capable of emulating a quantized primordial power spectrum.

We explicitly construct a double-field inflationary model, which satisfies the latest Planck constraints at the cosmic microwave background (CMB) scales and produces the whole dark matter energy density as primordial black holes (PBHs), in the mass range ${10}^{-17}{M}_{\odot }\lesssim M_{\mathrm{PBH}}\lesssim {10}^{-13}{M}_{\odot }$. The PBHs can be produced after the end of slow-roll inflation from the bubbles of true vacuum that nucleate during the course of inflation. Obtaining PBHs in this mass range enforces the scale of inflation to be extremely low, ${10}^{-7}\lesssim H\lesssim {10}^{-3}\mathrm{GeV}$, which makes the efforts to observe gravitational waves at the CMB scales futile, although it is high enough to allow for a successful big bang nucleosynthesis. We will show that the shape of the mass distribution of the PBHs is dependent on how inflation ends and the Universe settles from the metastable direction to the true one. End of inflation can also be probed by examining the gravitational waves spectrum. In particular, we show that if exit from the rolling metastable direction to the true vacuum of the potential happens through a first-order phase transition after the end of slow-roll inflation, it leaves behind a stochastic gravitational wave background (SGWB), which is potentially observable by the Laser Interferometer Space Antenna. Examining the mass distribution of PBHs and possible SGWB from the end of inflation, we may be able to gain invaluable information about the end of inflation.

We review the effect that the choice of a uniform or logarithmic prior has on the Bayesian evidence and hence on Bayesian model comparisons when data provide only a one-sided bound on a parameter. We investigate two particular examples: the tensor-to-scalar ratio $r$ of primordial perturbations and the mass of individual neutrinos $m_{\nu }$, using the cosmic microwave background temperature and polarization data from Planck 2018 and the NuFIT 5.0 data from neutrino oscillation experiments. We argue that the Kullback–Leibler divergence, also called the relative entropy, mathematically quantifies the Occam penalty. We further show how the Bayesian evidence stays invariant upon changing the lower prior bound of an upper constrained parameter. While a uniform prior on the tensor-to-scalar ratio disfavors the $r$ extension compared to the base $\mathrm{\Lambda }\mathrm{CDM}$ model with odds of about $1:20$, switching to a logarithmic prior renders both models essentially equally likely. $\mathrm{\Lambda }\mathrm{CDM}$ with a single massive neutrino is favored over an extension with variable neutrino masses with odds of $20:1$ in case of a uniform prior on the lightest neutrino mass, which decreases to roughly $2:1$ for a logarithmic prior. For both prior options we get only a very slight preference for the normal over the inverted neutrino hierarchy with Bayesian odds of about $3:2$ at most.

We introduce our approaches, in particular, the modifications of the primitive recovery procedure, to handle bare quark stars in numerical relativity simulations. Reliability and convergence of our implementation are demonstrated by evolving two triaxially rotating quark star models with different mass as well as a differentially rotating quark star model which has sufficiently large kinetic energy to be dynamically unstable. These simulations allow us to verify that our method is capable of resolving the evolution of the discontinuous surface of quark stars and possible mass ejection from them. The evolution of the triaxial deformation and the properties of the gravitational-wave emission from triaxially rotating quark stars are also studied, together with the mass ejection of the differentially rotating case. We find that supramassive quark stars are not likely to be ideal sources of a continuous gravitational wave as the star recovers axisymmetry much faster than models with smaller mass and gravitational-wave amplitude decays rapidly in a timescale of 10 ms, although the instantaneous amplitude from more massive models is larger. As with the differentially rotating case, our result confirms that quark stars could experience nonaxisymmetric instabilities similar to the neutron star case but with a quite small degree of differential rotation, which is expected according to previous initial-data studies.

The recent measurement of the spectra of intermediate-mass nuclei and iron nuclei carried out with the AMS-02 experiment provided us with the most complete set of data on cosmic-ray fluxes to date, and allowed us to test the standard model for the transport of these particles through the Galaxy to the finest details. We show that the parameters derived from lighter primary and secondary elements in the cosmic radiation also lead to a good description of the data on heavier nuclei, with no need to invoke different injection spectra for such nuclei, provided the whole chain of fragmentation is properly accounted for. The only exception to this finding is represented by iron nuclei, which show a very unusual trend at rigidity $\lesssim 100\mathrm{GV}$. This trend reflects in a Fe/O ratio that is at odds with the results of the standard model of cosmic-ray transport, and is in contradiction with data collected by HEAO, ACE-CRIS and Voyager at lower energy. We speculate on possible origins of such findings.

Stimulated by the exciting progress in experiments, we carry out a combined analysis of the masses, and strong and radiative decay properties of the $B$ and $B_s$-meson states up to the second orbital excitations. Based on our good descriptions of the mass and decay properties for the low-lying well-established states $B_1(5721)$, $B_2^{*}(5747)$, $B_{s1}(5830)$ and $B_{s2}^{*}(5840)$, we give a quark model classification for the high mass resonances observed in recent years. It is found that (i) the $B_J(5840)$ resonance may be explained as the low mass mixed state $B(|SD{⟩}_L)$ via $2{{}^{3}S}_1-1{{}^{3}D}_1$ mixing, or the pure $B(2{{}^{3}S}_1)$ state, or $B(2{{}^{1}S}_0)$. (ii) The $B_J(5970)$ resonance may be assigned as the $1{{}^{3}D}_3$ state in the $B$ meson family, although it as a pure $2{{}^{3}S}_1$ state cannot be excluded. (iii) The narrow structure around 6064 MeV observed in the $B^{+}{K}^{-}$ mass spectrum at LHCb may be mainly caused by the $B_{sJ}(6109)$ resonance decaying into $B^{*+}{K}^{-}$, and favors the assignment of the high mass $1D$-wave mixed state $B_s(1D_2^{\prime })$ with $J^P=2^{-}$, although it as the $1{{}^{3}D}_3$ state cannot be excluded. (iv) The relatively broader $B_{sJ}(6114)$ structure observed at LHCb may be explained with the mixed state $B_s(|SD{⟩}_H)$ via $2{{}^{3}S}_1-1{{}^{3}D}_1$ mixing, or a pure $1{{}^{3}D}_1$ state. Most of the missing $1P$-, $1D$-, and $2S$-wave $B$- and $B_s$-meson states have a relatively narrow width, they are most likely to be observed in their dominant decay channels with a larger data sample at LHCb.

We propose a muon-proton collider with asymmetrical multi-TeV beam energies and integrated luminosities of $0.1–1{\mathrm{ab}}^{-1}$. With its large center-of-mass energies and yet small Standard Model background, such a machine can not only improve electroweak precision measurements but also probe new physics beyond the Standard Model to an unprecedented level. We study its potential in measuring the Higgs properties, probing the R-parity-violating supersymmetry, as well as testing heavy new physics in the muon $g-2$ anomaly. We find that for these physics cases the muon-proton collider can perform better than both the ongoing and future high-energy collider experiments.

The effective photon-quark-antiquark ($\gamma q\overline{q}$) vertex function is evaluated at finite temperature in the presence of an arbitrary external magnetic field using the two-flavor gauged Nambu–Jona-Lasinio model in the mean field approximation. The lowest order diagram contributing to the magnetic form factor and the anomalous magnetic moment (AMM) of the quarks is calculated at finite temperature and external magnetic field using the imaginary time formalism of finite temperature field theory and the Schwinger proper time formalism. The Schwinger propagator, including all the Landau levels with nonzero AMM of the dressed quarks, is considered while calculating the loop diagram. Using sharp as well as smooth three-momentum cutoff, we regularize the UV divergences arising from the vertex function and the parameters of our model are chosen to reproduce the well-known phenomenological quantities at zero temperature and zero magnetic field, such as pion-decay constant ($f_{\pi }$), vacuum quark condensate, and vacuum pion mass ($m_{\pi }$), as well as the magnetic moments of proton and neutron. We then study the temperature and magnetic field dependence of the AMM and constituent mass of the quark. We found that the AMM as well as the constituent quark mass are large at the chiral symmetry broken phase in the low temperature region. Around the pseudo-chiral phase transition, they decrease rapidly and at high temperatures both of them approach vanishingly small values in the symmetry restored phase.

We study the time evolution of a complex scalar field in the symmetry broken phase in the presence of oscillating spacetime metric background. In our ($2+1$)-dimensional simulations, we show that the spacetime oscillations can excite an initial field configuration, which ultimately leads to the formation of topological vortices in the system. At late times, field configuration achieves a disordered state. A detailed study of the momentum and frequency modes of the field reveals that these field excitations are driven by the phenomenon of parametric resonance. In the extremely-high-frequency regime where frequency of spacetime oscillations is much larger than the field-mass, the formed vortices are not topological in nature. Interestingly, in this regime, for a suitable choice of parameters of the simulation, we observe a persistent lattice structure of vortex-antivortex pairs. We discuss applications of our study to the dynamics of interior superfluidity of neutron stars during binary neutron star mergers, in generation of excitation in ultralight axionlike field near a strong gravitational wave source, etc.

Recently, based on a new procedure to quantize the theory in the continuum, it was argued that Singer’s theorem points toward the existence of a Yang-Mills ensemble. In the new approach, the gauge fields are mapped into an auxiliary field space used to initially determine sectors labeled by center vortices, and then separately fix the gauge on them. In this work, we study this procedure in more detail. We provide examples of configurations belonging to these sectors and discuss the existence of non-Abelian degrees of freedom. Then, we discuss the importance of the mapping injectivity, and show that this property holds infinitesimally for typical configurations of the vortex-free sector and for the simplest example in the one-vortex sector. Finally, we show that these examples are free from Gribov copies.

We improve our previous variational method based nonrelativistic quark model by introducing a complete set of three-dimensional harmonic oscillator bases as the spatial part of the total wave function. To assess the validity of our approach, we compare the binding energy thus calculated with the exact value for the hydrogen model. After fitting to the masses of the ground state hadrons, we apply our new method to analyzing the doubly heavy tetraquark states $q{q}^{\prime }\overline{Q}\overline{Q^{\prime }}$ and compare the results for the binding energies to results in other works. We also calculate the ground state masses of $T_{sc}(ud\overline{s}\overline{c})$ and $T_{sb}(ud\overline{s}\overline{b})$ with $(I,S)=(0,1),(0,2)$. We find that $T_{bb}(ud\overline{b}\overline{b})$ and $us\overline{b}\overline{b}$, both with $(I,S)=(0,1)$, are stable against the two lowest threshold meson states with binding energies $-145$ and $-42\mathrm{MeV}$, respectively. We further find that $T_{cb}(ud\overline{c}\overline{b})$ is near the lowest threshold. The spatial sizes for the tetraquarks are also discussed.

The extraction of neutrino mixing parameters from accelerator-based neutrino-oscillation experiments relies on proper modeling of neutrino-nucleus scattering processes using neutrino interaction event generators. Experimental tests of these generators are difficult due to the broad range of neutrino energies produced in accelerator-based beams and the low statistics of current experiments. Here we overcome these difficulties by exploiting the similarity of neutrino and electron interactions with nuclei to test neutrino event generators using high-precision inclusive electron-scattering data. To this end, we revised the electron-scattering mode of the genie event generator ($e$-genie) to include electron-nucleus bremsstrahlung radiation effects and to use, when relevant, the exact same physics models and model parameters, as the standard neutrino-scattering version. We also implemented new models for quasielastic (QE) scattering and meson exchange currents (MECs) based on the theory-inspired super scaling approach SuSAv2. Comparing the new $e$-genie predictions with inclusive electron-scattering data, we find an overall adequate description of the data in the QE- and MEC-dominated lower energy transfer regime, especially when using the SuSAv2 models. Higher energy transfer interactions, which are dominated by resonance production, are still not well modeled by $e$-genie.

We show that an iterative solution of rapidity evolution equations with a leading-order kernel renders the entire signature-odd tower of next-to-next-to-leading logarithmic (NNLL) contributions to partonic $2\to 2$ amplitudes in the Regge limit computable in full color. The result, which universally holds in any gauge theory, corresponds to a set of three-Reggeon ladder diagrams. In this setting we compute the NNLL amplitude to four loops in dimensional regularization through finite corrections. Furthermore, by contrasting the result with the exponentiation properties of soft singularities we determine the four-loop correction to the soft anomalous dimension at this logarithmic accuracy. The latter features quartic Casimir contributions beyond those appearing in the cusp anomalous dimension. Finally, in the case of $\mathcal{N}=4$ super Yang-Mills, we also determine the finite hard function at four loops through NNLL in full color.