We show that existing laboratory experiments have the potential to unveil the origin of matter by probing leptogenesis in the type-I seesaw model with three right-handed neutrinos and Majorana masses in the GeV range. The baryon asymmetry is generated by $CP$-violating flavor oscillations during the production of the right-handed neutrinos. In contrast to the case with only two right-handed neutrinos, no degeneracy in the Majorana masses is required. The right-handed neutrinos can be found in meson decays at Belle II and LHCb.

As a first step to generalize the structure of loop quantum cosmology to the theories with the spacetime dimension other than four, the isotropic model of loop quantum cosmology in $2+1$ dimension is studied in this paper. We find that the classical big bang singularity is again replaced by a quantum bounce in the model. The similarities and differences between the ($2+1$)-dimensional model and the ($3+1$)-dimensional one are also discussed.

We analyze the behavior of blackbody radiation in theories of electromagnetism which allow the electron charge and the fine structure constant to vary in space and time. We show that such theories can be expressed as relativistic generalizations of a conventional dielectric. By making the appropriate definition of the vector potential and associated gauge transformations, we can identify the equivalent of the electric and displacement fields, $\mathbf{E}$ and $\mathbf{D}$, as well as the magnetic $\mathbf{B}$ and $\mathbf{H}$ fields. We study the impact of such dielectrics on the propagation of light in the so-called “BSBM” theory. We examine the form of simple cosmological solutions and conclude that no changes are created to the standard cosmological evolution of the temperature and energy density of blackbody radiation. Nonetheless the matter evolution changes and the behavior of the entropy per baryon is modified, and the ratios of different dark matter components may be changed too.

The paper deals with the mechanism of particle creation in the framework of irreversible thermodynamics. The second order nonequilibrium thermodynamical prescription of Israel and Stewart has been presented with particle creation rate, treated as the dissipative effect. In the background of a flat Friedmann-Robertson-Walker (FRW) model, we assume the nonequilibrium thermodynamical process to be isentropic so that the entropy per particle does not change and consequently the dissipative pressure can be expressed linearly in terms of the particle creation rate. Here the dissipative pressure behaves as a dynamical variable having a nonlinear inhomogeneous evolution equation and the entropy flow vector satisfies the second law of thermodynamics. Further, using the Friedmann equations and by proper choice of the particle creation rate as a function of the Hubble parameter, it is possible to show (separately) a transition from the inflationary phase to the radiation era and also from the matter dominated era to late time acceleration. Also, in analogy to analytic continuation, it is possible to show a continuous cosmic evolution from inflation to late time acceleration by adjusting the parameters. It is found that in the de Sitter phase, the comoving entropy increases exponentially with time, keeping entropy per particle unchanged. Subsequently, the above cosmological scenarios have been described from a field theoretic point of view by introducing a scalar field having self-interacting potential. Finally, we make an attempt to show the cosmological phenomenon of particle creation as Hawking radiation, particularly during the inflationary era.

We compute the parametrized post-Newtonian (PPN) parameters $\gamma$ and $\beta$ for general scalar-tensor theories in the Einstein frame, which we compare to the existing PPN formulation in the Jordan frame for alternative theories of gravity. This computation is important for scalar-tensor theories that are expressed in the Einstein frame, such as chameleon and symmetron theories, which can incorporate hiding mechanisms that predict environment-dependent PPN parameters. We introduce a general formalism for scalar-tensor theories and constrain it using the limit on $\gamma$ given by the Cassini experiment. In particular, we discuss massive Brans-Dicke scalar fields for extended sources. Next, using a recently proposed Earth satellite experiment, in which atomic clocks are used for spacecraft tracking, we compute the observable perturbations in the redshift induced by PPN parameters deviating from their general relativistic values. Our estimates suggest that $|\gamma -1|\sim |\beta -1|\sim {10}^{-6}$ may be detectable by a satellite that carries a clock with fractional frequency uncertainty $\mathrm{\Delta }f/f\sim {10}^{-16}$ in an eccentric orbit around the Earth. Such space experiments are within reach of existing atomic clock technology. We discuss further the requirements necessary for such a mission to detect deviations from Einstein relativity.

An electrostatic-controlled torsion pendulum combined with a scanning conducting probe is used to measure the temporal and spatial variations of the surface potential on test mass. The apparatus can work in static and scanning modes. Temporal variation of the surface potential can be measured with the static mode, and its voltage variation with a level of $15\mu \mathrm{V}/{\mathrm{Hz}}^{1/2}$ at 0.03 Hz has been achieved for a $5\times 5{\mathrm{mm}}^2$ area. The spatial distribution of the surface potential can be measured with the scanning mode, and the surface potential distribution can be obtained at a level of $330\mu \mathrm{V}$ at 0.125 mm spatial resolution. The experimental results tell us that the apparatus provide a new way to investigate the charge distribution and its variation, which is very useful in helping to understand the physical mechanism of the surface charge distribution of an actual object.

We investigate the strong vertices among the ${\mathrm{\Lambda }}_b$, nucleon, and $B$ meson as well as the ${\mathrm{\Lambda }}_c$, nucleon, and $D$ meson in QCD. In particular, we calculate the strong coupling constants $g_{{\mathrm{\Lambda }}_{b}NB}$ and $g_{{\mathrm{\Lambda }}_{c}ND}$ for different Dirac structures entering the calculations. In the case of the ${\mathrm{\Lambda }}_{c}ND$ vertex, we compare the result with the only existing prediction obtained at $Q^2=0$.

We propose a new class of inflation models in supergravity with higher derivative terms. In those models, the Kähler potential does not contain the inflaton multiplet, but a supersymmetric derivative term does. In the models, inflation is effectively driven by a single scalar field with a standard kinetic term and a scalar potential. Remarkably, the so-called $\eta$ problem does not exist in our models.

We rederive semishortening conditions for four-dimensional superconformal field theory with a different approach. These conditions have similar patterns that can be generalized to weaker constraints, including all those of Dolan and Osborn [Ann. Phys. (Amsterdam) 307, 41 (2003)]. In particular, for the case of $\mathcal{N}=4$ super-Yang-Mills theory formulated in projective superspace, we find constraints for all Bogomol’nyi-Prasad-Sommerfield operators. We also give an example how constraints can be found from known ones. These constraints are a subset of our maximal set of semishortening conditions.

Darboux transformations are employed in construction and analysis of Dirac Hamiltonians with pseudoscalar potentials. By this method, we build a four-parameter class of reflectionless systems. Their potentials correspond to the composition of complex kinks, also known as twisted kinks, that play an important role in the $1+1$ Gross-Neveu and Nambu–Jona-Lasinio field theories. The twisted kinks turn out to be multisolitonic solutions of the integrable Ablowitz-Kaup-Newell-Segur hierarchy. Consequently, all the spectral properties of the Dirac reflectionless systems are reflected in a nontrivial conserved quantity, which can be expressed in a simple way in terms of Darboux transformations. We show that the four-parameter pseudoscalar systems reduce to well-known models for specific choices of the parameters. An associated class of transparent nonrelativistic models described by a matrix Schrödinger Hamiltonian is studied and the rich algebraic structure of their integrals of motion is discussed.

In the case of general relativity, one can interpret the Noether charge in any bulk region as the heat content $TS$ of its boundary surface. Furthermore, the time evolution of the spacetime metric in Einstein’s theory arises due to the difference ($N_{\text{sur}}-N_{\text{bulk}}$) of suitably defined surface and bulk degrees of freedom. We show that this thermodynamic interpretation generalizes in a natural fashion to all Lanczos-Lovelock models of gravity. The Noether charge, related to the time evolution vector field, in a bulk region of space is equal to the heat content $TS$ of the boundary surface with the temperature $T$ defined by using local Rindler observers and $S$ being the Wald entropy. Using the Wald entropy to define the surface degrees of freedom $N_{\text{sur}}$ and the Komar energy density to define the bulk degrees of freedom $N_{\text{bulk}}$, we can also show that the time evolution of the geometry is sourced by ($N_{\text{sur}}-N_{\text{bulk}}$). When it is possible to choose the foliation of spacetime such that the metric is independent of time, the above dynamical equation yields the holographic equipartition for Lanczos-Lovelock gravity with $N_{\text{sur}}=N_{\text{bulk}}$. The implications are discussed.

We study the motion of a charged particle around a weakly magnetized rotating black hole. We classify the fate of a charged particle kicked out from the innermost stable circular orbit. We find that the final fate of the charged particle depends mostly on the energy of the particle and the radius of the orbit. The energy and the radius in turn depend on the initial velocity, the black hole spin, and the magnitude of the magnetic field. We also find possible evidence for the existence of bound motion in the vicinity of the equatorial plane.

We study the process of quantum tunnelling in scalar-tensor theories in which the scalar field is nonminimally coupled to gravity. In these theories gravitational instantons can deviate substantially from sphericity and can in fact develop a neck—a feature prohibited in theories with minimal coupling. Such instantons with necks lead to the materialization of bubble geometries containing a wormhole region. We clarify the relationship of neck geometries to violations of the null energy condition, and also derive a bound on the size of the neck relative to that of the instanton.

Nonlinear, ghost-free massive gravity has two tensor fields; when both are dynamical, the mass of the graviton can lead to cosmic acceleration that agrees with background data, even in the absence of a cosmological constant. Here the question of the stability of linear perturbations in this bimetric theory is examined. Instabilities are presented for several classes of models, and simple criteria for the cosmological stability of massive bigravity are derived. In this way, we identify a particular self-accelerating bigravity model, infinite-branch bigravity (IBB), which exhibits both viable background evolution and stable linear perturbations. We discuss the modified gravity parameters for IBB, which do not reduce to the standard $\mathrm{\Lambda }\mathrm{CDM}$ result at early times, and compute the combined likelihood from measured growth data and type Ia supernovae. IBB predicts a present matter density ${\mathrm{\Omega }}_{m0}=0.18$ and an equation of state $w(z)=-0.79+0.21z/(1+z)$. The growth rate of structure is well approximated at late times by $f(z)\approx {\mathrm{\Omega }}_m^{0.47}[1+0.21z/(1+z)]$. The implications of the linear instability for other bigravity models are discussed: the instability does not necessarily rule these models out, but rather presents interesting questions about how to extract observables from them when linear perturbation theory does not hold.

Relative locality is a recent approach to the quantum-gravity problem which allows the taming of nonlocality effects which may arise in some models which try to describe Planck-scale physics. I here explore the effect of relative locality on basic special-relativistic phenomena. In particular I study the deformations due to relative locality of special-relativistic transformation laws for momenta at all orders in the rapidity parameter $\xi$. I underline how those transformations also define the relative locality characteristic (momentum-dependent) invariant metric. I focus my analysis on the well studied de Sitter momentum-space framework, and I investigate the differences and similarities between this model and special relativity, from the definition of the boost parameter $\gamma$ to a first discussion of transverse effects characteristic of relative locality on clocks observables.

We construct new finite-energy regular solutions in Einstein–Yang-Mills-SU(2) theory. They are static, axially symmetric and approach at infinity the anti–de Sitter spacetime background. These configurations are characterized by a pair of integers $(m,n)$, where $m$ is related to the polar angle and $n$ to the azimuthal angle, being related to the known flat-space monopole-antimonopole chains and vortex rings. Generically, they describe composite configurations with several individual components, possessing a nonzero magnetic charge, even in the absence of a Higgs field. Such Yang-Mills configurations exist already in the probe limit, with the AdS geometry supplying the attractive force needed to balance the repulsive force of Yang-Mills gauge interactions. The gravitating solutions are constructed by numerically solving the elliptic Einstein-DeTurck–Yang-Mills equations. The variation of the gravitational coupling constant $\alpha$ reveals the existence of two branches of gravitating solutions which bifurcate at some critical value of $\alpha$. The lower-energy branch connects to the solutions in the global AdS spacetime, while the upper branch is linked to the generalized Bartnik-McKinnon solutions in asymptotically flat spacetime. Also, a spherically symmetric, closed-form solution is found as a perturbation around the globally anti–de Sitter vacuum state.

The quasinormal spectrum of a charged scalar field around a nonextremal Reissner-Nordström black hole, especially in the limit of large electromagnetic interaction, has been comprehensively studied only very recently. In this paper, we extend the analysis to Dirac fields using the continued fraction method and compare the results with the scalar case. In particular, we study the behavior of the fundamental quasinormal mode as a function of the black hole’s charge and of the electromagnetic interaction parameter. We derive an analytical formula for the quasinormal frequencies in the limit of large electromagnetic interaction. As the extremal limit of black hole charge is approached, we show that, unlike the case of neutral fields, the imaginary part of the quasinormal frequencies approaches zero for charged fields.

A stationary observer in the Kerr spacetime has zero angular momentum if their angular velocity $\omega$ has a particular value, which depends on the position of the observer. Worldlines of such zero-angular-momentum observers (ZAMOs) with the same value of the angular velocity $\omega$ form a three-dimensional surface, which has the property that the Killing vectors generating time translation and rotation are tangent to it. We call such a surface a rigidly rotating ZAMO surface. This definition allows for a natural generalization to the surfaces inside the black hole, where ZAMO trajectories formally become spacelike. A general property of such a surface is that there exist linear combinations of the Killing vectors with constant coefficients which make them orthogonal on it. In this paper we discuss properties of the rigidly rotating ZAMO surfaces both outside and inside the black hole and the relevance of these objects to a couple of interesting physical problems.

The ability of a plasma surrounding spinning black holes to extract rotational energy and power energetic emissions has been recognized as a key astrophysical phenomenon. Important insights into the nature of this process are obtained through the analysis of the interplay between a force-free magnetosphere and the black hole. This task involves solving a complicated system of equations, often requiring complex numerical simulations. Recent analytical attempts at tackling this problem have exploited the fact that the near-horizon region of extreme Kerr (NHEK) is endowed with an enhanced symmetry group. We continue in this direction and show that for some conformally self-similar solutions, the NHEK force-free equations reduce to a single nonlinear ordinary differential equation which is difficult to solve with straightforward integration. We here introduce a new approach specifically tailored to this problem and describe how one can obtain physically meaningful solutions.