We explore a novel method of describing the radiation friction of particles traveling through a mechanically resistive medium. We introduce a particle motion induced matter warping along the path in a manner assuring that charged particle dynamics occurs subject to radiative energy loss described by the Larmor formula. We compare our description with the Landau-Lifshitz-like model for the radiation friction and show that the established model exhibits nonphysical behavior. Our approach predicts in the presence of large mechanical friction an upper limit on radiative energy loss being equal to the energy loss due to the mechanical medium resistance. We demonstrate that mechanical friction due to strong interactions, for example of quarks in quark-gluon plasma, can induce significant soft photon radiation.

We propose a new mechanism for generating matter-antimatter asymmetry via the interference of tree-level diagrams only, where the imaginary part of the Breit-Wigner propagator for an unstable mediator plays a crucial role. We first derive a general result that a nonzero $CP$-asymmetry can be generated via at least two sets of interfering tree-level diagrams involving either $2\to 2$ or $1\to n$ (with $n\ge 3$) processes. We illustrate this point in a simple TeV-scale extension of the Standard Model with an inert Higgs doublet and right-handed neutrinos, along with an electroweak-triplet scalar field, where small Majorana neutrino masses are generated via a combination of radiative type-I and tree-level type-II seesaw mechanisms. The imaginary part needed for the required $CP$-asymmetry comes from the trilinear coupling of the inert doublet with the triplet scalar, along with the width of the triplet scalar mediator. The real part of the neutral component of the inert doublet serves as a cold dark matter candidate. The evolutions of the dark matter relic density and the baryon asymmetry are intimately related in this scenario.

We analyze the production of a light charged Higgs boson at the Large Hadron Collider (LHC) via the quark-fusion mechanism $c\overline{b}\to H^{-}$ considering the decay channel $H^{-}\to \tau {\overline{\nu }}_{\tau }$ in the final state. We study this process in the framework of the two-Higgs-doublet model type III (2HDM-III) which assumes a four-zero texture in the Yukawa matrices and a general Higgs potential, wherein the two Higgs doublets coupling to both up and down fermions do generate flavor-changing neutral currents, yet the latter can be controlled by the texture when flavor physics constraints are considered. We consider the parameter space of the model where this signal is enhanced and in agreement with both theoretical constraints and experimental data. In particular, we exploit the setup with lepton-specific-like Yukawa couplings and assess the LHC sensitivity to such $H^{\pm }$ signals against the dominant irreducible and reducible backgrounds. We show that in our model $\mathrm{BR}(H^{\pm }\to cb)\sim 0.1–0.2$ and $\mathrm{BR}(H^{\pm }\to \tau \nu )\sim 0.7–0.9$ so that, under these conditions the prospects for $H^{\pm }$ detection in the 2HDM-III in the aforementioned production and decay channels are excellent assuming standard collider energy and luminosity conditions.

We investigate the chiral phase structure of three flavor QCD in a background $U(1)$ magnetic field using the standard staggered action and the Wilson plaquette gauge action. We perform simulations on lattices with a temporal extent of $N_{\tau }=4$ and four spatial extents of $N_{\sigma }=8$, 16, 20 and 24. We choose a quark mass in lattice spacing as $am=0.030$ with corresponding pion mass estimated as $m_{\pi }\sim 280\mathrm{MeV}$ such that there exists a crossover transition at vanishing magnetic fields, and adopt two values of magnetic field strength in lattice spacing $a\sqrt{eB}\simeq 1.5$ and 2 corresponding to $eB/m_{\pi }^2\sim 11$ and 20, respectively. We find that the transition becomes stronger in the presence of a background magnetic field, and turns into a first order as seen from the volume scaling of the order parameter susceptibility as well as the metastable states in the time history of the chiral condensate. On the other hand, the chiral condensate and transition temperature always increase with $B$ even within the regime of a first order phase transition. This suggests that the discrepancy in the behavior of chiral condensates and transition temperature as a function of $B$ between earlier lattice studies using larger-than-physical pion masses with standard staggered fermions and those using physical pions with improved staggered fermions is mainly due to lattice cutoff effects.

The in-medium behavior of ground-state $q\overline{q}$ mesons, where $q\in \{u,d,s,c\}$, in vector and axial-vector channels is studied based on the spectral analysis for mesonic correlators at finite temperature and zero chemical potential. We first compute the correlators by solving the quark gap equations and the inhomogeneous Bethe-Salpeter equations in the rainbow-ladder approximation. Using a phenomenological ansatz, the spectral functions are extracted by fitting the correlators. By analyzing the evolution of the spectral functions with the temperature, we obtain the dissociation temperatures of mesons and discuss their relations to the critical temperature of the chiral symmetry restoration. The results show a pattern of flavor dependence of the thermal dissociation of the mesons.

We consider a detailed account on the construction of the heavy-quark parton distribution functions for charm and bottom, starting from $n_f=3$ light flavors in the fixed-flavor-number (FFN) scheme and by using the standard decoupling relations for heavy quarks in QCD. We also account for two-mass effects. Furthermore, different implementations of the variable-flavor-number (VFN) scheme in deep-inelastic scattering (DIS) are studied, with the particular focus on the resummation of large logarithms in $Q^2/m_h^2$, the ratio of the virtuality of the exchanged gauge boson $Q^2$ to the heavy-quark mass squared $m_h^2$. Little impact of resummation effects is found in the kinematic range of the existing data on the DIS charm-quark production so that they can be described very well within the FFN scheme. Finally, we study the theoretical uncertainties associated to the VFN scheme, which manifest predominantly at small $Q^2$.

In charmed $D$ and $D_s$ mesons sector, the matrix of a Hamiltonian in a quark potential model is computed in the $2^3{S}_1$ and $1^3{D}_1$ subspace. The masses of four mixed states of $2^3{S}_1$ and $1^3{D}_1$ denoted with $D_1^{*}(2635)$, $D_1^{*}(2739)$, $D_{s1}^{*}(2715)$ and $D_{s1}^{*}(2805)$ are obtained. It is an off-diagonal part of the spin-orbit tensor interaction that causes the mixing between the $2^3{S}_1$ and $1^3{D}_1$ states. The mixing angles between the $2^3{S}_1$ and $1^3{D}_1$ states are tiny. Under the mixing, a ${}^3{P}_0$ model is employed to compute the hadronic decay widths of all OZI-allowed decay channels of the four mixed states. The two light mixed states $D_1^{*}(2635)$ and $D_{s1}^{*}(2715)$ are close in mass to $D_J^{*}(2600)$ and $D_{s1}^{*}(2700)$, while the two heavy mixed states $D_1^{*}(2739)$ and $D_{s1}^{*}(2805)$ are lighter in mass than $D(2750)$ and $D_{s1}^{*}(2860)$. The mixing angles obtained from dynamical interaction are inconsistent with the mixing angles obtained from hadronic decay. Based on mass spectra and hadronic decay analyses, $D_J^{*}(2600)$, $D(2750)$, $D_{s1}^{*}(2700)$, and $D_{s1}^{*}(2860)$ are impossibly the mixed states of $2^3{S}_1$ and $1^3{D}_1$ at the small mixing angles. The inconsistence implies that $D_1^{*}(2760)$ and $D_{s1}^{*}(2860)$ have not been properly resolved from present experimental data, or there exist large unknown off-diagonal interactions that result in large mixing angles.

We introduce an infinite set of jet substructure observables, derived as projections of $N$-point energy correlators, that both are convenient for experimental studies and maintain remarkable analytic properties derived from their representations in terms of a finite number of light ray operators. We show that these observables can be computed using tracking or charge information with a simple reweighting by integer moments of nonperturbative track or fragmentation functions. Our results for the projected $N$-point correlators are analytic functions of $N$, allowing us to derive resummed results to next-to-leading logarithmic accuracy for all $N$. We analytically continue our results to noninteger values of $N$ and define a corresponding analytic continuation of the observable, which we term a $\nu$ correlator, that can be measured on jets of hadrons at the LHC. This enables observables that probe the leading twist collinear dynamics of jets to be placed into a single analytic family, which we hope will lead to new insights into jet substructure.

The axial-vector form factors and axial-vector constants of the baryon decuplet are investigated within a pion mean-field approach, which is also known as the chiral quark-soliton model. Given an axial-vector current with a specified flavor, there are four different form factors of a decuplet baryon. When we consider the singlet, triplet, and octet axial-vector currents, we have twelve different form factors for each member of the baryon decuplet. We compute all these axial-vector form factors of the baryon decuplet, taking into account the rotational $1/N_c$ corrections and effects of flavor SU(3) symmetry breaking. We find that, for a given flavor, two of the form factors for a decuplet baryon are only independent within the present approach. We first examine properties of the axial-vector form factors of the ${\mathrm{\Delta }}^{+}$ isobar and ${\mathrm{\Omega }}^{-}$ hyperon. We also compare the results of the triplet axial-vector form factors of ${\mathrm{\Delta }}^{+}$ with those from lattice QCD and those of the present work for the axial-vector constants of the baryon decuplet with the lattice data. All the results for other members of the baryon decuplet are then presented. The results of the axial charges are compared with those of other works. The axial masses and axial radii are also discussed.

By considering radiative corrections of up to 3rd-loop order, Ritus and Narozhny conjectured that the proper expansion parameter for QED in a strong constant crossed field is $g=\alpha {\chi }^{2/3}$, where the dynamical quantum parameter $\chi =e\sqrt{-(Fp{)}^2}/m^3$ combines the particle momentum $p$ with the external field strength tensor $F$. Here we present and discuss the first nonperturbative result in this context, the resummed bubble-type polarization corrections to the electron self-energy in a constant crossed field. Our analysis confirms the relevance of the scaling parameter $g$ to the enhancement of bubble-type radiative corrections. This parameter actually represents the characteristic value of the ratio of the 1-loop polarization bubble to the photon virtuality. After an all-order resummation we identify and discuss two contributions to the self-energy with different formation regions and asymptotic behavior for $g\gg 1$. Whereas the breakdown of perturbation theory occurs already for $g\gtrsim 1$, the leading-order result remains dominant until the asymptotic regime $g\gg 1$ is reached. However, the latter is specific to processes like elastic scattering or photon emission and does not have to remain true for general higher-order QED processes.

An accelerated charged particle emits electromagnetic radiation. If the driving force is sufficiently strong, the radiated energy becomes comparable to the kinetic energy of the particle and the backaction of the emitted radiation (radiation reaction) significantly alters the dynamics of the particle. The Landau-Lifshitz (LL) equation has been proposed as the classical equation to describe the dynamics of a charged particle in a strong electromagnetic field when the effects of radiation reaction are taken into account. Hitherto, the experimental problem in validating the LL equation has been to achieve sufficiently strong fields for the radiation reaction to be important without quantum effects being prominent. Notwithstanding, here we provide a quantitative experimental test of the LL equation by measuring the emission spectrum for a wide range of settings for 50 GeV positrons crossing aligned silicon single crystals near the (110) planar channeling regime as well as 40 and 80 GeV electrons traversing aligned diamond single crystals near the $⟨100⟩$ axial channeling regime. The experimental spectra are in remarkable agreement with predictions based on the LL equation of motion with small quantum corrections for recoil and, in case of electrons, spin and reduced radiation emission, as well as with a more elaborate quantum mechanical model. Our experiment clearly shows the inadequacy of the Lorentz force as the sole agent of force on the particles in the classical limit, due to its absence of radiative energy loss in describing the dynamics of high-energy charged particles in strong electromagnetic fields like those in aligned single crystals.

The hierarchical three-body problem has many applications in relativistic astrophysics and can play an important role in the formation of the binary black hole mergers detected by LIGO/Virgo. However, many studies have only included relativistic corrections responsible for the precession of the pericenter of the inner and outer binaries, neglecting relativistic interactions between the three bodies. We revisit this problem and develop a fully consistent derivation of the secular three-body problem to first post-Newtonian order. We start with the Einstein-Infeld-Hoffman equations for a three-body system and expand the accelerations as a power series in the ratio of the semimajor axes of the inner ($a_1$) and outer ($a_2$) binary. We then perform a post-Keplerian, two-parameter expansion of the single-orbit-averaged Lagrange planetary equations in $\delta =v^2/c^2$ and $\epsilon =a_1/a_2$ using the method of multiple scales. Using this method, we derive previously identified secular effects at $\delta {\epsilon }^{5/2}$ order that arise directly from the equations of motion. We also calculate new secular effects through $\delta {\epsilon }^4$ order that can lead to eccentricity growth over many Lidov-Kozai cycles when the tertiary is much more massive than the inner binary. In such cases, inclusion of these effects can substantially alter the evolution of three-body systems as compared to an analysis in which they are neglected. Careful analysis of post-Newtonian three-body effects will be important to understand the formation and properties of coalescing binaries that form via three-body dynamical processes.

High energy collision of massive bodies is investigated without fine tuning. We study multiple collisions of two spherical concentric shells in a gravitationally bound system and calculate the center of mass energy between the shells. We solve the equation of motions for two shells without imposing any fine tuning of the initial parameters. In this bound system, the shells collide many times, and these motions are highly nontrivial due to chaotic behavior of the shells. Consequently, the center of mass energy for each collision varies nontrivially and even reaches almost its theoretical upper limit. We confirm that a significant proportion of the theoretical limit is automatically achieved during multiple collisions without fine tuning. At the same time, we also study shell ejection from the system after some collisions. If the initial shell’s energy is large enough, multiple collisions may cause one shell to accumulate energy so that it escapes to infinity, even though the two shells are initially confined in the system. The ejection is caused by multiple collisions inducing nontrivial energy transfer between the shells. The relation between the maximum center of mass energy and the energy transfer causing the shell ejection is also discussed.

Vector-tensor theories beyond General Relativity have widely been studied in the context of ultraviolet completion of gravity, endowing a mass to the graviton and explaining dark energy phenomena. We here construct rotating black hole solutions in vector-tensor theories valid after the binary neutron star merger event GW170817 that placed very stringent bound on the propagation speed of gravitational waves away from the speed of light. Such valid vector-tensor theories are constructed by performing a generic conformal transformation to Einstein-Maxwell theory, and the new rotating black hole solutions are constructed by applying the same conformal transformation to the Kerr-Newman solution. These theories fall outside of beyond generalized Proca theories but are within an extended class of vector-tensor theories that satisfy a degenerate condition to eliminate instability modes and are thus healthy. We find that such conformal Kerr-Newman solutions preserve the location of the singularities, event horizons, and ergoregion boundary from Kerr-Newman, as well as the multipole moments and the Petrov type. On the other hand, the Hamilton-Jacobi equation is no longer separable, suggesting that the Carter-like constant does not exist in this solution. The standard Newman-Janis algorithm also does not work to construct the new solutions. We also compute the epicyclic frequencies, the location of the innermost stable circular orbits, and the Schwarzschild precession and apply the latter to the recent GRAVITY measurement to place bounds on the deviations away from Kerr-Newman for Sgr A*.

In a scalar-coupled-gravity model, the quadratically divergent counterterm appearing in the mass renormalization of the scalar fields must inherit corrections arising out of gravitational interactions. In this work we have explicitly demonstrated that there are no such corrections of gravitational origin to the quadratic divergences in the mass counter terms. This statement holds true irrespective of the nature of the gravitational interaction, i.e., whether gravity is described by general relativity or f(R) theory. Interestingly, it also turns out that the one loop effective action of scalar-coupled-gravity system will be well-behaved if and only if the $f(R)$ theory is free from ghosts. In particular, the results derived in the context of f(R) theory are shown to be in exact agreement with the corresponding results derived from the equivalent scalar-tensor representation. Our analysis suggests the tantalizing possibility that the masses of the scalar fields can be consistently kept smaller than some ultraviolet (UV) cutoff scale and is independent of the nature of the gravity theory, which may involve higher curvature corrections. All these will be true provided the matter fields and the gravity theory can be embedded consistently into a UV complete theory at the Planck scale.

The area of a future holographic screen increases monotonically. This area can be associated with entropy, resulting in a generalized second law for cosmology (GSLC). However, such an area law has no thermodynamical interpretation, in contrast to black hole horizons. We propose a thermodymical interpretation by relating the screen area to a phase space by means of a geometrical construction. This enables us to uniquely identify the direction of foliation necessary in order to present the entropy of any holographic screen as entropy derived from phase space. Moreover, by construction, this allows us to associate a specific temperature with each holographic screen. In the case of accelerated observers, these quantities coincide with the entropy and temperature that they detect due to their acceleration. Thus, using the equivalence principle, we obtain a thermodynamical interpretation for the GSLC.

Cosmological adiabatic particle creation results in the generation of irreversible entropy. The evolution of this entropy is examined in a flat Friedmann-Robertson-Walker universe at late times, using a dissipative model with a power-law term (proportional to the power of the Hubble parameter $H$). In a dissipative universe, the irreversible entropy included in the Hubble volume is found to be proportional to $H^{-1}$, unlike for the case of the Bekenstein-Hawking entropy on the horizon of the universe. In addition, the evolution of the horizon entropy is examined, extending the previous analysis of a nondissipative universe [Phys. Rev. D 100, 123545 (2019)]. In the present model, the generalized second law of thermodynamics is always satisfied, whereas the maximization of entropy is satisfied under specific conditions. The dissipative universe should be constrained by the entropy maximization as if the universe behaves as an ordinary, isolated macroscopic system. The thermodynamic constraints are likely to be consistent with constraints on a transition from a decelerating universe to an accelerating universe.

We describe inflation in terms of a time-dependent quantum density matrix with time playing the role of a stochastic variable. Using a quasi-de Sitter model we compute the corresponding quantum Fisher information function as the second derivative of the relative entanglement entropy for the density matrix at two different times. Employing standard quantum estimation theory we evaluate the minimal variance of quantum scalar fluctuations that reproduces the power spectrum and the corresponding tilt in the slow-roll limit. The Jeffreys prior associated with such Fisher information can be used to define the probabilities on the set of initial conditions defined by the slow-roll parameter $\epsilon$ and the initial Shannon information.

We update the constraints on the location of the nearest ultrahigh energy cosmic ray (UHECR) source. By analyzing recent data from the Pierre Auger Observatory using state-of-the-art CR propagation models, we reaffirm the need of local sources with a distance less than 25–100 Mpc, depending on mass composition. A new fast semianalytical method for the propagation of UHECR in environments with turbulent magnetic fields is developed. The onset of an enhancement and a low-energy magnetic horizon of cosmic rays from sources located within a particular distance range is demonstrated. We investigate the distance to the nearest source, taking into account these magnetic field effects. The results obtained highlight the robustness of our constrained distances to the nearest source.

On April 1st, 2019, the Advanced Laser Interferometer Gravitational-Wave Observatory (aLIGO), joined by the Advanced Virgo detector, began the third observing run, a year-long dedicated search for gravitational radiation. The LIGO detectors have achieved a higher duty cycle and greater sensitivity to gravitational waves than ever before, with LIGO Hanford achieving angle-averaged sensitivity to binary neutron star coalescences to a distance of 111 Mpc, and LIGO Livingston to 134 Mpc with duty factors of 74.6% and 77.0% respectively. The improvement in sensitivity and stability is a result of several upgrades to the detectors, including doubled intracavity power, the addition of an in-vacuum optical parametric oscillator for squeezed-light injection, replacement of core optics and end reaction masses, and installation of acoustic mode dampers. This paper explores the purposes behind these upgrades, and explains to the best of our knowledge the noise currently limiting the sensitivity of each detector.