In this paper, we discuss the universality of the renormalization of the gauge coupling constant in the quantum electrodynamics coupled to the Einstein’s gravity in the framework of effective field theory in an arbitrary gauge. We observe that the renormalization of the three-point functions with different particles receive different contributions from the gravitational sector. Despite that, the universality of the gauge coupling constants is guaranteed by the Ward identity that makes the renormalized electric charge receive no contribution from the gravitational sector at one-loop order.

We demonstrate how plane fronted waves with colliding wave fronts are the asymptotic limit of spherical electromagnetic and gravitational waves. In the case of the electromagnetic waves we utilize Bateman’s representation of radiative solutions of Maxwell’s vacuum field equations. The gravitational case involves a novel form of the radiative Robinson-Trautman solutions of Einstein’s vacuum field equations.

Dynamical properties of a generic null surface are known to have a thermodynamic interpretation. Such an interpretation is completely based on an analogy between the usual law of thermodynamics and structure of gravitational field equation on the surface. Here we materialize this analogy and show that assigning a temperature on the null surface for a local observer is indeed physically relevant. We find that for a local frame, chosen as outgoing massless chargeless particle (or field mode), perceives a “local unstable Hamiltonian” very near to the surface. Due to this it has finite quantum probability to escape through acausal null path which is given by Maxwell-Boltzmann like distribution, thereby providing a temperature on the surface.

Two ways to deduce the equivalence of the field equations of general relativity and the principle of maximum force $c^4/4G$, or the equivalent maximum power $c^5/4G$, are presented. A simple deduction of inverse square gravity directly from maximum force arises. Recent apparent counter arguments are refuted. New tests of the principle in astronomy, cosmology, electrodynamics, numerical gravitation, and quantum gravity are proposed.

Spontaneous scalarization of neutron stars has been extensively studied in the Damour and Esposito-Farèse model, in which a scalar field couples to the Ricci scalar or, equivalently, to the trace of the energy-momentum tensor. However, scalarization of both black holes and neutron stars may also be triggered by a coupling of the scalar field to the Gauss-Bonnet invariant. The case of the Gauss-Bonnet coupling has also received a lot of attention lately, but the synergy of the Ricci and Gauss-Bonnet couplings has been overlooked for neutron stars. Here, we show that combining both couplings has interesting effects on the properties of scalarized neutron stars, such as affecting their domain of existence or the amount of scalar charge they carry.

We compute tail contributions to the conservative dynamics of a generic self-gravitating system, for every multipole order, of either electric and magnetic parity. Such contributions arise when gravitational radiation is backscattered by the static curvature generated by the source itself and reabsorbed. Tail processes are relevant for the study of compact binary dynamics starting from the fourth post-Newtonian order. Within this context, we resolve a discrepancy recently arised at fifth post-Newtonian order between effective field theory and self-force results.

In this article we explore local Lorentz transformations in theories of gravity based on the teleparallel formalism. For the teleparallel equivalent of general relativity (TEGR), the spin connection plays no role in the equations of motion; therefore, it is possible to simply put it equal to zero with no change in physical quantities, and then the theory is formulated purely in terms of the tetrad field which can be freely chosen in any way. In nonlinear modifications of TEGR, this is a more intricate issue, and vanishing spin connection is then the Weitzenböck gauge choice which imposes restrictions on the choice of tetrad. This has led to considering the so-called covariant formulation of $f(T)$ gravity. We examine the primary constraints arising when passing to the Hamiltonian framework and compute their algebra. We show that the problems of local Lorentz symmetry breaking still appear in this formulation, even if in a different disguise.

The bispectrum is the leading non-Gaussian statistic in large-scale structure, carrying valuable information on cosmology that is complementary to the power spectrum. To access this information, we need to model the bispectrum in the weakly nonlinear regime. In this work we present the first two-loop, i.e. next-to-next-to-leading order perturbative description of the bispectrum within an effective field theory (EFT) framework. Using an analytic expansion of the perturbative kernels up to $F_6$ we derive a renormalized bispectrum that is demonstrated to be independent of the UV cutoff. We show that the EFT parameters associated with the four independent second-order EFT operators known from the one-loop bispectrum are sufficient to absorb the UV sensitivity of the two-loop contributions in the double-hard region. In addition, we employ a simplified treatment of the single-hard region, introducing one extra EFT parameter at two-loop order. We compare our results to $N$-body simulations using the realization-based grid perturbation theory method and find good agreement within the expected range, as well as consistent values for the EFT parameters. The two-loop terms start to become relevant at $k\approx 0.07h{\mathrm{Mpc}}^{-1}$. The range of wave numbers with percent-level agreement, independently of the shape, extends from $0.08$ to $0.15h{\mathrm{Mpc}}^{-1}$ when going from one to two loops at $z=0$. In addition, we quantify the impact of using exact instead of Einstein–de-Sitter kernels for the one-loop bispectrum, and discuss in how far their impact can be absorbed into a shift of the EFT parameters.

We analyze the uncertainties introduced in the determination of the neutron star matter proton fraction, in a range of densities close to the saturation density, if the cold $\beta$-equilibrium neutron star matter equation of state (EOS) is known. In particular, we discuss the effect of neglecting the muon contribution and of considering that the energy density of nuclear matter is well described by taking only terms until second order in the proton-neutron asymmetry. It is shown that two types of uncertainties may be associated with the extraction of the symmetry energy from the $\beta$-equilibrium EOS: an overestimation if terms above the parabolic approximation on the asymmetry parameter are neglected, or an underestimation if the muon contribution is not considered. The effect of the uncertainty on the symmetric nuclear matter EOS on the determination of the proton fraction is discussed. It could be shown that the neutron star mass-radius curve is sensitive to the parabolic approximation on the asymmetry parameter.

We propose a novel, frequency-domain approach to the analysis of the gravitational-wave ringdown signal of binary black holes and the identification of quasinormal mode frequencies of the remnant. Our approach avoids the issues of spectral leakage that would normally be expected (associated with the abrupt start of the ringdown) by modeling the inspiral and merger parts of the signal using a flexible sum of sine-Gaussian wavelets truncated at the onset of the ringdown. Performing the analysis in the frequency domain allows us to use standard (and by now well-established) Bayesian inference pipelines for gravitational-wave data as well as giving us the ability to readily search over the sky position and the ringdown start time, although we find that it is necessary to use an informative prior for the latter. We test our method by using it to analyze several simulated signals with varying signal-to-noise ratios injected into two- and three-detector networks. We find that our frequency-domain approach is generally able to place tighter constraints on the remnant black-hole mass and spin than a standard time-domain analysis.

Matched filtering is a traditional method used to search a data stream for signals. If the source (and hence its $n$ parameters) are unknown, many filters must be employed. These form a grid in the $n$-dimensional parameter space, known as a template bank. It is often convenient to construct these grids as lattices. The simplest of these, ${\mathbb{Z}}^n$, is used in both continuous gravitational-wave and gamma-ray pulsar searches; we wanted to investigate how much might be gained by replacing it with the more elaborate $A_n^{*}$ lattice. To determine this, we calculate the distribution of the mismatch function, both in the traditional quadratic approximation and with the recently proposed spherical ansatz. The fraction of signals which are lost is determined by the even moments of this distribution, which we find. Many of these quantities have a simple and well-defined $n\to \infty$ limit, which often gives an accurate estimate even for small $n$. Our main conclusions are the following: (i) a fairly effective template-based search can be constructed at mismatch values that are shockingly high in the quadratic approximation; (ii) the minor advantage offered by an $A_n^{*}$ template bank (compared to ${\mathbb{Z}}^n$) at small template separation becomes even less significant for large template spacings. In most cases, the gain from employing an $A_n^{*}$ lattice is not enough to justify the increase in complexity.

In this paper, we study the simultaneous evolution of baryon asymmetry and hypermagnetic field amplitude assuming an early matter domination. We contrast our results to the conventional case where radiation domination during early universe is assumed. We show that the baryon asymmetry and the hypermagntic field amplitude can change by orders of magnitude if we assume a nonstandard history of cosmology. That is because the Hubble rate determines which processes are efficient. We find that a change in Hubble rate can have a significant impact on when the weak sphalerons become active. As a result of a change in the evolution of baryonic asymmetry, alters the evolution of hypermagnetic field amplitude. It is known that if the hypermagnetic field amplitude is large enough, it can save the baryon asymmetry from diminishing. We show that whether a small seed of hypermagnetic field amplitude can be amplified to a large enough value will strongly depend on the history of cosmology.

We present a novel baryogenesis mechanism in which the asymmetry is sourced from heavy particles which either gain their mass or are created during bubble expansion in a strong first order phase transition. These particles then decay in a $CP$ and baryon number violating way inside the bubble. The particles are inherently out of equilibrium and sufficiently dilute after wall crossing so the third Sakharov condition is easily met. Washout is avoided provided the reheat temperature is sufficiently below the scale of the heavy particles. The mechanism relies on moderate supercooling and relativistic walls which—in contrast to electroweak baryogenesis—generically leads to a sizable gravitational wave signal, although in the simplest realizations at frequencies beyond upcoming detectors. We present a simple example model and discuss the restrictions on the parameter space for the mechanism to be successful. We find that high reheat temperatures $T_{\mathrm{RH}}\gtrsim {10}^{10}\mathrm{GeV}$ are generally preferred, whereas stronger supercooling allows for temperatures as low as $T_{\mathrm{RH}}\sim {10}^6\mathrm{GeV}$, provided the vacuum energy density is sufficiently suppressed. We briefly comment on using resonantly enhanced $CP$ violation to achieve even lower scales.

Mirage mediation realized in the Kachru-Kallosh-Linde-Trivedi (KKLT) flux compactification can naturally suppress the up-type Higgs soft mass at low-energy scales. As a result, compared to the conventional scenarios, the degree of electroweak fine-tuning can be reduced further up to by a loop factor if the Higgsinos are much lighter than the heavy Higgs doublet. Interestingly, this feature holds even in high-scale supersymmetry as long as the gauge coupling unification, which is required as a prerequisite for mirage mediation, accommodates such light Higgsinos. Under the experimental constraints on the observed Higgs boson, it turns out that mirage mediation can exhibit low electroweak fine-tuning better than a few percent for stops between about 2 TeV and 6 TeV, i.e., at the same level as in the weak-scale supersymmetry, if the Higgsinos are around or below a few hundred GeV.

We present a model which connects the neutral current $B$ anomalies with composite Higgs models. The model is based on the minimal fundamental composite Higgs model with $SU(4)/Sp(4)$ coset. The strong dynamics spontaneously break the symmetry and introduce five Nambu-Goldstone bosons. Four of them become the Standard Model Higgs doublet, and the last one, corresponding to the broken local $U(1{)}^{\prime }$ symmetry, is eaten by the gauge boson. This leads to an additional TeV-scale $Z^{\prime }$ boson, which can explain the recent $B$ anomalies. The experimental constraints and allowed parameter space are discussed in detail.

The production of vector mesons in the fragmentation process of polarized quarks is studied within the recursive $\mathrm{string}+{{}^{3}P}_0$ model, improving a previous version of the model in which the production of pseudoscalar mesons only was considered. Two types of couplings of the vector meson to quarks are introduced, their coupling constants being the additional free parameters of the model. The angular distribution of the decay products of the polarized vector meson is deduced from the spin density matrix of the meson and the spin information is propagated along the fragmentation chain taking into account the entanglement of spin states. The new model is implemented in a stand alone Monte Carlo program utilized to investigate in detail kinematic distributions and transverse spin asymmetries. The sensitivity of these observables to the new free parameters is discussed and the Monte Carlo results are compared with experimental data on transverse spin asymmetries.

We have systematically calculated the mass spectra for S-wave and P-wave fully charm $c\overline{c}c\overline{c}$ and fully bottom $b\overline{b}b\overline{b}$ tetraquark states in the ${\mathbf{8}}_{[Q\overline{Q}]}\otimes {\mathbf{8}}_{[Q\overline{Q}]}$ color configuration, by using the moment QCD sum rule method. The masses for the fully charm $c\overline{c}c\overline{c}$ tetraquark states are predicted about 6.3–6.5 GeV for S-wave channels and 7.0–7.2 GeV for P-wave channels. These results suggest the possibility that there are some ${\mathbf{8}}_{[c\overline{c}]}\otimes {\mathbf{8}}_{[c\overline{c}]}$ components in LHCb’s di-$J/\psi$ structures. For the fully bottom $b\overline{b}b\overline{b}$ system, their masses are calculated around 18.2 GeV for S-wave tetraquark states while 18.4–18.8 GeV for P-wave ones, which are below the ${\eta }_b{\eta }_b$ and $\mathrm{\Upsilon }(1S)\mathrm{\Upsilon }(1S)$ two-meson decay thresholds.

We evaluate the hadronic contribution to the $g-2$ of the muon by deriving the low-energy limit of QCD and computing in this way the hadronic vacuum polarization. The low-energy limit is a nonlocal Nambu-Jona-Lasinio model that has all the parameters fixed from QCD, and the only experimental input used is the confinement scale that is known from measurements of hadronic physics. Our estimations provide a novel analytical alternative to the current lattice computations and we find that our result is close to the similar computation performed from experimental data. We also comment on how this analytical approach technique, in general, may provide prospective estimates for hadronic computations from dark sectors and its implication in beyond Standard Model building in future.

We study the nature of the recently observed $P_{cs}(4459)$ by the LHCb collaboration by employing three methods based on the elastic effective-range expansion and the resulting size of the effective-range, the saturation of the compositeness relation and width of the resonance, and a direct fit to data involving the channels $J/\psi \mathrm{\Lambda }$, ${\mathrm{\Xi }}_c^{\prime }\overline{D}$, and ${\mathrm{\Xi }}_c{\overline{D}}^{*}$. We have also considered the addition of a Castillejo-Dalitz-Dyson (CDD) pole but this scenario can be discarded. Our different analyses clearly indicate the molecular nature of the $P_{cs}(4459)$ with a clear ${\mathrm{\Xi }}_c{\overline{D}}^{*}$ dominant component. In relation with heavy-quark-spin symmetry our results also favor the actual existence of two resonances with $J=1/2$ (the lighter one) and $3/2$ (the heavier one) in the energy region of the $P_{cs}(4459)$. In the scenario of two-resonance for the $P_{cs}(4459)$, the inclusion of the ${\mathrm{\Xi }}_c^{\prime }\overline{D}$ channel is required for their mass splitting and it allows one to determine the spin structures of the two resonances.