In isotropic but Lorentz- and $CPT$-violating electrodynamics, it is known that a charge in uniform motion does not lose any energy to Cerenkov radiation. This presents a puzzle, since the radiation appears to be kinematically allowed for many modes. Studying the Fourier transforms of the most important terms in the modified magnetic field and Poynting vector, we confirm the vanishing of the radiation rate. Moreover, we show that the Fourier transform of the field changes sign between small and large wave numbers. This enables modes with very long wavelengths to carry negative energies, which cancel out the positive energies carried away by modes with shorter wavelengths. This cancelation had previously been inferred but never explicitly demonstrated.

We study the electroweak phase transition in the framework of the scalar singlet-doublet mixed dark matter model, in which the particle dark matter candidate is the lightest neutral Higgs that comprises the $CP$-even component of the inert doublet and a singlet scalar. The dark matter can be dominated by the inert doublet or singlet scalar depending on the mixing. We present several benchmark models to investigate the two situations after imposing several theoretical and experimental constraints. An additional singlet scalar and the inert doublet drive the electroweak phase transition to be strongly first order. A strong first-order electroweak phase transition and a viable dark matter candidate can be accomplished in two benchmark models simultaneously, for which a proper mass splitting among the neutral and charged Higgs masses is needed.

We present a numerical study of three-dimensional two-color QCD with $N=0$, 2, 4, 8 and 12 flavors of massless two-component fermions using parity-preserving improved Wilson-Dirac fermions. A finite volume analysis provides strong evidence for the presence of $Sp(N)$ symmetry-breaking bilinear condensate when $N\le 2$ and its absence for $N\ge 8$. A weaker evidence for the bilinear condensate is shown for $N=4$. We estimate the critical number of flavors below which scale-invariance is broken by the bilinear condensate to be between $N=4$ and 6.

The mechanism of confinement in Yang-Mills theories remains a challenge to our understanding of nonperturbative gauge dynamics. While it is widely perceived that confinement may arise from chromomagnetically charged gauge configurations with nontrivial topology, it is not clear what types of configurations could do that and how, in pure Yang-Mills and QCD-like (nonsupersymmetric) theories. Recently, a promising approach has emerged, based on statistical ensembles of dyons/anti-dyons that are constituents of instanton/anti-instanton solutions with nontrivial holonomy where the holonomy plays a vital role as an effective “Higgsing” mechanism. We report a thorough numerical investigation of the confinement dynamics in $SU(2)$ Yang-Mills theory by constructing such a statistical ensemble of correlated instanton-dyons.

Low-energy effective couplings of baryons’ constituent quarks to light vector and axial mesons are derived by considering quark polarization for a dressed one gluon–exchange quark interaction. The quark field is split into two components, one for background constituent quarks and another one for quark-antiquark states, light mesons, and the scalar chiral condensate. By considering a large quark effective mass derivative expansion, several effective coupling constants are resolved as functions of the original model parameters and of components of the quark and gluon propagators. Besides the leading single vector meson–constituent quark gauge–type effective coupling, several two-vector and axial meson–constituent quark couplings are also obtained in the next leading order. Among these, vector and axial mesons mixings induced by constituent quark currrents are found. Approximated and exact ratios between the effective coupling constants in the limit of very large quark effective mass and numerical estimates are exhibited. Numerical results of the corresponding form factors and of the (strong) vector mesons quadratic radius are also presented.

We study the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\eta \gamma$, where the photon is radiated from the initial state. About 8000 fully reconstructed events of this process are selected from the BABAR data sample with an integrated luminosity of $469{\mathrm{fb}}^{-1}$. Using the ${\pi }^{+}{\pi }^{-}\eta$ invariant mass spectrum, we measure the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\eta$ cross section in the $e^{+}{e}^{-}$ center-of-mass energy range from 1.15 to 3.5 GeV. The cross section is well described by the Vector-Meson dominance model with four $\rho$-like states. We observe $49\pm 9$ events of the $J/\psi$ decay to ${\pi }^{+}{\pi }^{-}\eta$ and measure the product ${\mathrm{\Gamma }}_{J/\mathrm{\Psi }\to e^{+}{e}^{-}}{\mathcal{B}}_{J/\mathrm{\Psi }\to {\pi }^{+}{\pi }^{-}\eta }=2.34\pm 0.43_{\mathrm{stat}}\pm 0.16_{\mathrm{syst}}\mathrm{eV}$.

In previous work, we outlined a worldline framework that can be used for systematic computations of the chiral magnetic effect (CME) in ultrarelativistic heavy-ion collisions. Towards this end, we first expressed the real part of the fermion determinant in the QCD effective action as a supersymmetric worldline action of spinning, colored, Grassmanian point particles in background gauge fields, with equations of motion that are covariant generalizations of the Bargmann-Michel-Telegdi and Wong equations. The chiral anomaly, in contrast, arises from the phase of the fermion determinant. Remarkably, the latter too can be expressed as a point particle worldline path integral, which can be employed to derive the anomalous axial vector current. We will show here how Berry’s phase can be obtained in a consistent nonrelativistic adiabatic limit of the real part of the fermion determinant. Our work provides a general first principles demonstration that the topology of Berry’s phase is distinct from that of the chiral anomaly confirming prior arguments by Fujikawa in specific contexts. This suggests that chiral kinetic treatments of the CME in heavy-ion collisions that include Berry’s phase alone are incomplete. We outline the elements of a worldline covariant relativistic chiral kinetic theory that captures the physics of how the chiral current is modified by many-body scattering and topological fluctuations.

In general relativity (GR), linearized gravitational waves propagating in empty Minkowski spacetime along a fixed spatial direction have the property that the wave front is the Euclidean plane. Beyond the linear regime, exact plane waves in GR have been studied theoretically for a long time and many exact vacuum solutions of the gravitational field equations are known that represent plane gravitational waves. These have parallel rays and uniform wave fronts. It turns out, however, that GR also admits exact solutions representing gravitational waves propagating along a fixed direction that are nonplanar. The wave front is then nonuniform and the bundle of rays is twisted. We find a class of solutions representing nonplanar unidirectional gravitational waves and study some of the properties of these twisted waves.

The cuscuton is a scalar field with infinite speed of propagation. It was introduced in the context of cosmology but it has also been claimed to resemble Hořava gravity in a certain limit. Here we revisit the cuscuton theory as a Lorentz-violating gravity theory. We clarify its relation with Hořava gravity and Einstein-æther theory, analyze its causal structure, and consider its initial value formulation. Finally, we discuss to which extent the cuscuton theory can be used as a proxy for Hořava gravity in the context of gravitational collapse and formation of universal horizons.

In the Dynamical Dark-Matter (DDM) framework, the dark sector comprises a large number of constituent dark particles whose individual masses, lifetimes, and cosmological abundances obey specific scaling relations with respect to each other. In particular, the most natural versions of this framework tend to require a spectrum of cosmological abundances which scale inversely with mass, so that dark-sector states with larger masses have smaller abundances. Thus far, DDM model-building has primarily relied on nonthermal mechanisms for abundance generation such as misalignment production, since these mechanisms give rise to abundances that have this property. By contrast, the simplest versions of thermal freeze-out tend to produce abundances that increase, rather than decrease, with the mass of the dark-matter component. In this paper, we demonstrate that there exist relatively simple modifications of the traditional thermal freeze-out mechanism which “flip” the resulting abundance spectrum, producing abundances that scale inversely with mass. Moreover, we demonstrate that a far broader variety of scaling relations between lifetimes, abundances, and masses can emerge through thermal freeze-out than through the nonthermal mechanisms previously considered for DDM ensembles. The results of this paper thus extend the DDM framework into the thermal domain and essentially allow us to “design” our resulting DDM ensembles at will in order to realize a rich array of resulting dark-matter phenomenologies.

Under the influence of gravity, light scalar fields can form bound compact objects called boson stars. We use the semianalytic approach of matching asymptotic expansions to obtain the profile for boson stars where the constituent particles have self-interactions. We obtain parametric representations of these profiles as a function of the self-interactions, including the case of very strong self-interactions. We show that our methods agree with solutions obtained by purely numerical methods. Significant distortions are found as compared to the noninteracting case.

The supernova explosion which deposited ${}^{60}\mathrm{Fe}$ isotopes on Earth 2–3 million years ago should have also produced cosmic rays which contribute to the locally observed cosmic ray flux. We show that the contribution of this “local source” causes the “anomalies” observed in the positron and antiproton fluxes and explains why their spectral shapes agree with that of the proton flux. At the same time, this local source component accounts for the difference in the slopes of the spectra of cosmic ray nuclei as the result of the slightly varying relative importance of the “local” and the average component for distinct CR nuclei. Such a “local supernova” model for the spectra of nuclei can be tested via a combined measurement of the energy dependence of the boron-to-carbon (primary-to-secondary cosmic rays) ratio and of the antiproton spectrum: while the antiproton spectrum is predicted to extend approximately as a power law into the TeV range without any softening break, the B/C ratio is expected to show a “plateau” at a level fixed by the observed positron excess in the 30–300 GeV range. We discuss the observability of such a plateau with dedicated experiments for the measurement of the cosmic ray composition in the 10 TeV energy range (NUCLEON, ISS-CREAM).

This work sets out to compute and discuss effects of spin, velocity, and dimensionality on interparticle potentials systematically derived from gauge field-theoretic models. We investigate the interaction of fermionic particles by the exchange of a vector field in a parity-preserving description in five-dimensional (5D) space-time. A particular dimensional reduction prescription is adopted—reduction by dimensional restriction—and special effects, like a pseudospin dependence, show up in four dimensions (4D). What we refer to as pseudospin shall be duly explained. The main idea we try to convey is that the calculation of the potentials in five dimensions and the consequent reduction to four dimensions exhibits new effects that are not present if the potential is calculated in four dimensions after the action has been reduced.

A very simple variational approach to pure $\mathrm{SU}(N)$ Yang-Mills theory is proposed, based on the Gaussian effective potential in a linear covariant gauge. The method provides an analytical variational argument for mass generation. The method can be improved order by order by a perturbative massive expansion around the optimal trial vacuum. At finite temperature, a weak first-order transition is found (at $T_c\approx 250\mathrm{MeV}$ for $N=3$) where the mass scale drops discontinuously. Above the transition the optimal mass increases linearly as expected for deconfined bosons. The equation of state is found in good agreement with the lattice data.

We determine the normalization of scalar and pseudoscalar current operators made from nonrelativistic $b$ quarks and highly improved staggered light quarks in lattice quantum chromodynamics (QCD) through $\mathcal{O}({\alpha }_s)$ and ${\mathrm{\Lambda }}_{\mathrm{QCD}}/m_b$. We use matrix elements of these operators to extract $B$ meson decay constants and form factors, and then compare to those obtained using the standard vector and axial-vector operators. This provides a test of systematic errors in the lattice QCD determination of the $B$ meson decay constants and form factors. We provide a new value for the $B$ and $B_s$ meson decay constants from lattice QCD calculations on ensembles that include $u$, $d$, $s$, and $c$ quarks in the sea and those that have the $u/d$ quark mass going down to its physical value. Our results are $f_B=0.196(6)\mathrm{GeV}$, $f_{B_s}=0.236(7)\mathrm{GeV}$, and $f_{B_s}/f_B=1.207(7)$, agreeing well with earlier results using the temporal axial current. By combining with these previous results, we provide updated values of $f_B=0.190(4)\mathrm{GeV}$, $f_{B_s}=0.229(5)\mathrm{GeV}$, and $f_{B_s}/f_B=1.206(5)$.

We present a formalism that resums threshold-enhanced logarithms to all orders in perturbative QCD for the rapidity distribution of any colorless particle produced in hadron colliders. We achieve this by exploiting the factorization properties and $\mathrm{K}+\mathrm{G}$ equations satisfied by the soft and virtual parts of the cross section. We compute for the first time compact and most general expressions in two-dimensional Mellin space for the resummed coefficients. Using various state-of-the-art multiloop and multileg results, we demonstrate the numerical impact of our resummed results up to next-to-next-to-leading order for the rapidity distribution of the Higgs boson at the LHC. We find that inclusion of these threshold logs through resummation improves the reliability of perturbative predictions.

We calculate isolated photon production at forward rapidities in proton-nucleus collisions in the color glass condensate framework. Our calculation uses dipole cross sections solved from the running coupling Balitsky-Kovchegov equation with an initial condition fit to deep inelastic scattering data. For comparison, we also update the results for the nuclear modification factor for pion production in the same kinematics. We present predictions for future forward RHIC and LHC measurements at $\sqrt{s_{NN}}=200\mathrm{GeV}$ and $\sqrt{s_{NN}}=8\mathrm{TeV}$.

We address and solve a puzzle raised by a recent calculation [1] of the cross section for particle production in proton-nucleus collisions to next-to-leading order: the numerical results show an unreasonably large dependence upon the choice of a prescription for the QCD running coupling, which spoils the predictive power of the calculation. Specifically, the results obtained with a prescription formulated in the transverse coordinate space differ by 1 to 2 orders of magnitude from those obtained with a prescription in momentum space. We show that this discrepancy is an artifact of the interplay between the asymptotic freedom of QCD and the Fourier transform from coordinate space to momentum space. When used in coordinate space, the running coupling can act as a fictitious potential which mimics hard scattering and thus introduces a spurious contribution to the cross section. We identify a new coordinate-space prescription, which avoids this problem, and leads to results consistent with those obtained with the momentum-space prescription.

We investigate the inclusive Higgs boson production in proton-proton collisions at the CERN LHC conditions using the $k_T$-factorization approach. Our analysis is based on the dominant off-shell gluon-gluon fusion subprocess (where the transverse momenta of initial gluons are taken into account) and covers $H\to \gamma \gamma$, $H\to Z{Z}^{*}\to 4l$ (where $l=e$, $\mu$) and $H\to W^{+}{W}^{-}\to e^{\pm }{\mu }^{\mp }\nu \overline{\nu }$ decay channels. The transverse momentum dependent (or unintegrated) gluon densities in a proton were derived from Ciafaloni-Catani-Fiorani-Marchesini equation, which resums large logarithmic terms proportional to $\ln s\sim \ln 1/x$, important at high energies. As an alternative choice, we apply the Kimber-Martin-Ryskin prescription, where the transverse momentum dependent gluon density is constructed from the known conventional parton distributions. We estimate the theoretical uncertainties of our calculations and compare our results with next-to-next-to-leading-order plus next-to-next-to-leading-logarithmic ones obtained using collinear QCD factorization. Our predictions agree well with the latest experimental data taken by the CMS and ATLAS Collaborations at $\sqrt{s}=8$ and 13 TeV.