A general formal derivation of the screened massive expansion is provided by Schwinger-Dyson equations. Some known issues of the expansion are clarified and a more general framework is established for a natural extension of the method to two loop or to amplitudes that are not directly defined by a generating functional. For instance, a one-loop screened expansion is given for the effective gauge-parameter-independent gluon propagator that arises from the pinch technique.

Generalized parton distributions describe the correlations between the longitudinal momentum and the transverse position of quarks and gluons in a nucleon. They can be constrained by measuring photon leptoproduction observables, arising from the interference between Bethe-Heitler and deeply virtual Compton scattering (DVCS) processes. At leading-twist/leading-order, the amplitude of the latter is parametrized by complex integrals of the GPDs $\{H,E,\tilde{H},\tilde{E}\}$. As data collected on an unpolarized or longitudinally polarized target constrains $H$ and $\tilde{H}$, $E$ is poorly known as it requires data collected with a transversely polarized target, which is very challenging to implement in fixed-target experiments. The only alternative considered so far has been DVCS on a neutron with a deuterium target, while assuming isospin symmetry and absence of final-state interactions. Today, we introduce the polarization of the recoil proton as a new DVCS observable, highly sensitive to $E$, which appears feasible for an experimental study at a high-luminosity facility such as Jefferson Lab.

A symmetry preserving regularization procedure for dealing with the contact interaction model is proposed in this work. This regularization procedure follows a series of consistency conditions that are necessary to maintain gauge symmetry. Under this regularization, proofs for the preservation of the Ward-Takahashi identities are given and the loop integrals in the contact interaction model are systematically computed. As an application example, the kaon electromagnetic form factor and $K_{l3}$ transition form factor are computed, and self-consistent results are obtained. Since the proposed regularization properly handles the divergence, one is freed from the inconsistencies caused by the regularization and can concentrate more on the physical discussion.

Aiming on testing the ${\mathrm{\Xi }}_c-{\mathrm{\Xi }}_c^{\prime }$ mixing, we study the decays of ${\mathrm{\Xi }}_{cc}\to {\mathrm{\Xi }}_c\pi$ with ${\mathrm{\Xi }}_{cc}=({\mathrm{\Xi }}_{cc}^{++},{\mathrm{\Xi }}_{cc}^{+})$, ${\mathrm{\Xi }}_c=({\mathrm{\Xi }}_c^{(\prime )+},{\mathrm{\Xi }}_c^{(\prime )0})$ and $\pi =({\pi }^{+},{\pi }^0)$. The soft-meson limit is considered along with the pole model, and the baryon matrix elements are evaluated by the bag model with and without removing the center-of-mass motion (CMM). We find that the four-quark operator matrix elements are about two times larger once the unwanted CMM is removed. We obtain that $\mathcal{R}=\mathcal{B}({\mathrm{\Xi }}_{cc}^{+}\to {\mathrm{\Xi }}_c^{\prime +}{\pi }^{+})/\mathcal{B}({\mathrm{\Xi }}_{cc}^{+}\to {\mathrm{\Xi }}_c^{+}{\pi }^{+})={0.87}_{-0.11}^{+0.17}$ and 1.45 with and without removing the CMM, where the former is close to the lower bound and the later is well consistent with $\mathcal{R}=1.41\pm 0.17\pm 0.10$ measured at LHCb. In addition, we show that after including the mixing the up-down asymmetry of $\alpha ({\mathrm{\Xi }}_{cc}^{+}\to {\mathrm{\Xi }}_c^{(\prime )0}{\pi }^{+})$ flips sign. Explicitly, we obtain that $\alpha ({\mathrm{\Xi }}_{cc}^{+}\to {\mathrm{\Xi }}_c^{\prime +}{\pi }^0)=0.52$ and $\alpha ({\mathrm{\Xi }}_{cc}^{+}\to {\mathrm{\Xi }}_c^0{\pi }^{+})=0.31$ with and without the CMM corrections, respectively, which are all negative if the mixing is absence. As a bonus, a positive value of $\alpha ({\mathrm{\Xi }}_{cc}^{+}\to {\mathrm{\Xi }}_c^{\prime 0}{\pi }^{+})$ in experiments can also serve as the evidence of the $W$-exchange contributions.

Using a data sample of $(1.0087\pm 0.0044)\times {10}^{10}J/\psi$ decay events collected with the BESIII detector at the center-of-mass energy of $\sqrt{s}=3.097\mathrm{GeV}$, we present a search for the hyperon semileptonic decay ${\mathrm{\Xi }}^0\to {\mathrm{\Sigma }}^{-}{e}^{+}{\nu }_e$ which violates the $\mathrm{\Delta }S=\mathrm{\Delta }Q$ rule. No significant signal is observed, and the upper limit on the branching fraction $\mathcal{B}({\mathrm{\Xi }}^0\to {\mathrm{\Sigma }}^{-}{e}^{+}{\nu }_e)$ is determined to be $1.6\times {10}^{-4}$ at the 90% confidence level. This result improves the previous upper limit result by about one order of magnitude.

In this paper, we extend previous results on the quantum vacuum or Casimir energy, for a noninteracting rotating system and for an interacting nonrotating system, to the case where both rotation and interactions are present. Concretely, we first reconsider the noninteracting rotating case of a scalar field theory and propose an alternative and simpler method to compute the Casimir energy based on a replica trick and the Coleman-Weinberg effective potential. We then consider the simultaneous effect of rotation and interactions, including an explicit breaking of rotational symmetry. To study this problem, we develop a numerical implementation of zeta-function regularization. Our work recovers previous results as limiting cases and shows that the simultaneous inclusion of rotation and interactions produces nontrivial changes in the quantum vacuum energy. Besides expected changes (where, as the size of the ring increases for fixed interaction strength, the angular momentum grows with the angular velocity), we notice that the way rotation combines with the coupling constant amplifies the intensity of the interaction strength. Interestingly, we also observe a departure from the typical massless behavior where the Casimir energy is proportional to the inverse size of the ring.

The existence of light rings in a spacetime is closely related to the existence of black hole horizons and observables such as the ringdown and the shadow. Black holes, compared to nonvacuum ultracompact objects, have rather unique environments. To this aim, recently [P. V. P. Cunha and C. A. R. Herdeiro, Phys. Rev. Lett. 124, 181101 (2020)] topological arguments, independent of the underlying gravity theory, were developed to prove the existence of unstable light rings outside the Killing horizon of four dimensional asymptotically flat, stationary, axisymmetric, nonextremal black holes. Here we extend these arguments to five-dimensional stationary black holes. Generically in five dimensions, there are two possible conserved angular momenta, hence the four-dimensional discussion does not extend verbatim to five dimensions; nevertheless, we prove that there is a light ring for each rotation sense for a stationary black hole. We give the static and the Myers-Perry rotating black holes as examples. We also show that when the horizon of the black hole disappears and the singularity becomes naked, only one of the light rings survives; a similar phenomenon also occurs in four dimensions which might allow testing the cosmic censorship hypothesis.

Tilt-to-length (TTL) noise from angular jitter in LISA is projected to be the dominant noise source in the milli-Hertz band unless corrected in post-processing. The correction is only possible after removing the overwhelming laser phase noise using time-delay interferometry (TDI). We present here a frequency domain model that describes the effect of angular motion of all three spacecraft on the interferometric signals after propagating through TDI. We then apply a Fisher information matrix analysis to this model to calculate the minimum uncertainty with which TTL coupling coefficients may be estimated. Furthermore, we show the impact of these uncertainties on the residual TTL noise in the gravitational wave readout channel, and compare it to the impact of the angular witness sensors’ readout noise. We show that the residual TTL noise post-subtraction in the TDI variables for a case using the LISA angular jitter requirement and integration time of one day is limited to the $8\mathrm{pm}/\sqrt{\mathrm{Hz}}$ level by angular sensing noise. However, using a more realistic model for the angular jitter we find that the TTL coupling uncertainties are 70 times larger, and the noise subtraction is limited by these uncertainties to the $14\mathrm{pm}/\sqrt{\mathrm{Hz}}$ level.

The violation of charge conjugation ($C$) and parity ($P$) symmetries are a requirement for the observed dominance of matter over antimatter in the Universe. As an established effect of beyond the Standard Model physics, this could point towards additional $CP$ violation in the Higgs-gauge sector. The phenomenological footprint of the associated anomalous couplings can be small, and designing measurement strategies with the highest sensitivity is therefore of the utmost importance in order to maximize the discovery potential of the Large Hadron Collider. There are, however, very few measurements of $CP$-sensitive observables in processes that probe the weak-boson self-interactions. In this article, we study the sensitivity to new sources of $CP$ violation for a range of experimentally accessible electroweak processes, including $W\gamma$ production, $WW$ production via photon fusion, electroweak $Zjj$ production, electroweak $ZZjj$ production, and electroweak $W^{\pm }{W}^{\pm }jj$ production. We study simple angular observables as well $CP$-sensitive observables constructed using the outputs of machine-learning algorithms. We find that the machine-learning-constructed $CP$-sensitive observables improve the sensitivity to $CP$-violating effects by up to a factor of five, depending on the process. We also find that inclusive $W\gamma$ and electroweak $Zjj$ production have the potential to set the best possible constraints on certain $CP$-odd operators in the Higgs-gauge sector of dimension-six effective field theories.

Inflationary scenarios motivated by high-energy physics generically contain a plethora of degrees of freedom beyond the primordial curvature perturbation. The latter interacts in a simple way with what we name “inflationary flavor eigenstates,” which differ, in general, from freely propagating “mass eigenstates.” We show that the mixing between these misaligned states results in new striking behaviors in the squeezed limit of the curvature perturbation three-point function, depending not only on the mass spectrum but also on the “mixing angles” of the theory. These results bring about a new perspective on the cosmological collider program: contrary to a widespread belief, the primordial signal needs not be dominated by the lightest extra degree of freedom. Instead, we show that it may display either modulated oscillations, a broken power law, or a transition from oscillations to a power law, thus offering a detailed cosmic spectroscopy of the particle content of inflation.

We express the nonlocal Bondi-Metzner-Sachs (BMS) charges of a free massless Klein-Gordon scalar field in $2+1$ in terms of the Green functions of the polyharmonic operators. Using the properties of these Green functions, we are able to discuss the asymptotic behavior of the fields that ensures the existence of the charges and prove that one obtains a realization of the $2+1$ BMS algebra in canonical phase space. We also discuss the transformations in configuration space and show that in this case the algebra closes only up to skew-symmetric combinations of the equations of motion. The formulation of the charges in terms of Green functions opens the way to the generalization of the formalism to other dimensions and systems.

We examine the virtual transition of an atom-mirror system with the simultaneous emission of two scalar photons, where the atom and the mirror admit a relative acceleration between them. For the single photon emission, the literature [A. A. Svidzinsky et al., Phys. Rev. Lett. 121, 071301 (2018)] dictates that the transition probabilities of two individual systems, such as an atom accelerating with respect to the mirror and its reverse, turn out to be equivalent under the exchange of the frequencies of atom and the field. Addressing the observational merit of such excitation process, a detectable probability ($P\sim {10}^{-2}$) is also reported in the above literature. In the present manuscript our finding dictates that the simultaneous emission of dual photon instead of one, destroys the equivalence between the transition probabilities as reported in the above literature.

We estimate the accuracy in the measurement of the tidal Love number of a supermassive compact object through the detection of an extreme mass ratio inspiral (EMRI) by the future LISA mission. A nonzero Love number would be a smoking gun for departures from the classical black hole prediction of general relativity. We find that an EMRI detection by LISA could set constraints on the tidal Love number of a spinning central object with dimensionless spin $\widehat{a}=0.9$ ($\widehat{a}=0.99$), which are approximately four (six) orders of magnitude more stringent than what achievable with current ground-based detectors for stellar-mass binaries. Our approach is based on the stationary phase approximation to obtain approximate but accurate semianalytical EMRI waveforms in the frequency domain, which greatly speeds up high-precision Fisher-information matrix computations. This approach can be easily extended to several other tests of gravity with EMRIs and to efficiently account for multiple deviations in the waveform at the same time.

We compute the contribution to the two-body scattering angle of a specific class of interactions involving the exchange of gravitational radiative degrees of freedom, including the nonlinear memory process and square of radiation reaction effects. Our computation is performed directly from the equations of motion, thus computing the overall effect of both conservative and dissipative processes. Such contributions provide in principle the last missing ingredients to compute the scattering angle at fifth post-Newtonian and fourth post-Minkowskian order.

Symmetric teleparallel gravity is shown to be integrable in the presence of boundaries, given the consistent implementation of constraints in the covariant phase space formalism.

We develop a new nonlinear method to model structure formation in general relativity from a generalization of the relativistic Lagrangian perturbation schemes, controlled by Szekeres (and LTB) exact solutions. The overall approach can be interpreted as the evolution of a deformation field on an inhomogeneous reference model, obeying locally Friedmann-like equations. In the special case of locally one-dimensional deformations, the new model contains the entire Szekeres family of exact solutions. As thus formulated, this approach paraphrases the Newtonian and relativistic Zel’dovich approximations, having a large potential for applications in contexts where relativistic degrees of freedom are relevant. Numerical simulations are implemented to illustrate the capabilities and accuracy of the model.

We formulate the transition from decelerated to accelerated expansion as a bounce in connection space and study its quantum cosmology, knowing that reflections are notorious for bringing quantum effects to the fore. We use a formalism for obtaining a time variable via the demotion of the constants of nature to integration constants, and focus on a toy universe containing only radiation and a cosmological constant $\mathrm{\Lambda }$ for simplicity. We find that, beside the usual factor-ordering ambiguities, there is an ambiguity in the order of the quantum equation, leading to two distinct theories: one second order, and one first order. In both cases two time variables may be defined, conjugate to $\mathrm{\Lambda }$ and the radiation constant of motion. We make little headway with the second-order theory, but are able to produce solutions to the first-order theory. They exhibit the well-known “ringing” whereby incident and reflected waves interfere, leading to oscillations in the probability distribution even for well-peaked wave packets. We also examine in detail the probability measure within the semiclassical approximation. Close to the bounce, the probability distribution becomes double peaked, with one peak following a trajectory close to the classical limit but with a Hubble parameter slightly shifted downwards, and the other with a value of $b$ stuck at its minimum. An examination of the effects still closer to the bounce, and within a more realistic model involving matter and $\mathrm{\Lambda }$, is left to future work.

We continue examining statistical data assimilation, an inference methodology, to infer solutions to neutrino flavor evolution, for the first time using real—rather than simulated—data. The model represents neutrinos streaming from the Sun’s center and undergoing a Mikheyev-Smirnov-Wolfenstein resonance in flavor space, due to the radially varying electron number density. The model neutrino energies are chosen to correspond to experimental bins in the Sudbury Neutrino Observatory and Borexino experiments, which measure electron-flavor survival probability at Earth. The procedure successfully finds consistency between the observed fluxes and the model, if the Mikheyev-Smirnov-Wolfenstein resonance—that is, flavor evolution due to solar electrons—is included in the dynamical equations representing the model.

In agreement with the constantly increasing gravitational wave events, new aspects of the internal structure of compact stars can be considered. A scenario in which a first-order transition takes place inside these stars is of particular interest, as it can lead, under certain conditions, to a third gravitationally stable branch (besides white dwarfs and neutron stars), the twin stars. The new branch yields stars with the same mass as normal compact stars but quite different radii. We focus on hybrid stars undergoing a hadron-to-quark phase transition near their core and how this new stable configuration arises. Emphasis is given on the aspects of the phase transition and its parametrization in two different ways—namely, with the Maxwell and Gibbs constructions. We systematically study the gravitational mass, the radius, and the tidal deformability, and we compare them with the predictions of the recent observation by the LIGO/VIRGO Collaboration, the GW170817 event, and the mass and radius limits, suggesting possible robust constraints. Moreover, we extend the study to include rotation effects on the twin star configurations. The recent discovery of the fast rotating supermassive pulsar PSR J0952-0607 triggered the efforts to constrain the equation of state and, moreover, to examine possible predictions related to the phase transition in dense nuclear matter. We pay special attention to relate the PSR J0952-0607 pulsar properties to the twin star predictions, and mainly to explore the possibility that the existence of such a massive object would rule out the existence of twin stars. Finally, we discuss the constraints on the radius and mass of the recently observed compact object within the supernova remnant HESS J1731-347. The estimations imply that this object is either the lightest known neutron star or a star with a more exotic equation of state.

We consider the effects of strong gravitational lensing by galaxy-scale deflectors on the observations of high-energy ($\mathrm{E}\gg \mathrm{GeV}$) neutrinos (HENs). For HENs at cosmological distances, the optical depth for multiple imaging is $\sim {10}^{-3}$, implying that while we do not expect any multiply imaged HENs with present samples, next-generation experiments should be able to detect the first such event. We then present the distribution of expected time delays to aid in the identification of such events, in combination with directional and energy information. In order to assist in the evaluation of HEN production mechanisms, we illustrate how lensing affects the observed number counts for a variety of intrinsic luminosity functions of the source population. Finally, we see that the lensing effects on the cosmic neutrino background flux calculation would be negligible by taking kiloparsec-scale jets as an example.