We provide tools to analyze factorization at the amplitude level for processes involving the entire standard model. We focus in particular on a momentum region, in which the factorization of real and certain virtual corrections appears in a generalized eikonal approximation in which we expand around a quasisoft limit for massive gauge bosons, fermions, and scalars. We use the chirality-flow formalism to express loop exchanges or emissions as operators on chiral structures. This provides key tools for amplitude evolution with parton exchange and branching in the full Standard Model, including the electroweak sector.

The observation of the $T_{c\overline{s}}(2900)$ indicates the potential existence of strange double charm pentaquarks based on the heavy antidiquark symmetry. We systematically study the mass spectra of strange double charm pentaquarks with strangeness $S=-1$ in both molecular and compact structures for quantum numbers $J^P=1/2^{-}$, $3/2^{-}$, $5/2^{-}$. By constructing the interpolating currents, the mass spectra can be extracted from the two-point correlation functions in the framework of QCD sum rule method. In the molecular picture, we find that the ${\mathrm{\Xi }}_c^{\prime +}{D}^{*+}$, ${\mathrm{\Xi }}_c^{*+}{D}^{*+}$, ${\mathrm{\Xi }}_{cc}^{*++}{\overline{K}}^{*0}$, and ${\mathrm{\Omega }}_{cc}^{*+}{\rho }^{+}$ may form molecular strange double charm pentaquarks. In both pictures, the masses of the $J^P=1/2^{-},3/2^{-}$ pentaquarks locate within the 4.2–4.6 GeV and 4.2–4.5 GeV regions, respectively. As all of them are above the thresholds of their strong decay channels, they behave as a broad state, making them challenging to be detected experimentally. On the other hand, the strange double charm pentaquark with $J^P=5/2^{-}$ lies below its strong decay channel, which may be a very narrow state and easy to identify experimentally. The best observed channel is its semileptonic decay to double charm baryon. As the result, we strongly suggest experiments to search for $J^P=5/2^{-}$ strange double charm pentaquarks first.

Scattering amplitudes for the massless QCD process, $q\overline{q}\to q^{\prime }{\overline{q}}^{\prime }$, are calculated in the one-loop order in the Feynman-Diagram (FD) gauge, where gluons are quantized on the light cone with opposite direction of the three-momenta. We find non-decoupling of the Faddeev-Popov ghosts and nonconventional UV singularities in dimensional regularization. The known QCD amplitudes with asymptotic freedom are reproduced only after summing propagator and vertex corrections. By quantizing gluons in the Feynman gauge on the FD gauge background, we obtain the one-loop improved FD gauge amplitudes.

We study numerically the evolution of an expanding strongly self-coupled real scalar field. We use a conformally invariant action that gives a traceless energy-momentum tensor and is better suited to model the early time behavior of a system such as QCD, whose action is also conformally invariant. We consider asymmetric initial conditions and observe that when the system is initialized with nonzero spatial eccentricity, the eccentricity decreases and the elliptic flow coefficient increases. This behavior is characteristic of a hydrodynamic system in which pressure gradients are converted into fluid velocities, and therefore spatial anisotropy decreases while momentum anisotropy is generated. We look at a measure of transverse pressure asymmetry that has been shown to behave similarly to the elliptic flow coefficient in hydrodynamic systems and show that in our system their behavior is strikingly similar. We show that the derivative of the transverse velocity is proportional to the gradient of the energy in Milne coordinates and argue that this result means that transverse velocity initially develops in the same way that it does in hydrodynamic systems. We conclude that some aspects of the early onset of hydrodynamic behavior that has been observed in quark-gluon plasmas are seen in our numerical simulation of strongly coupled scalar fields.

The aim of this paper is to derive limits on various forms of “new physics” using atomic experimental data. Interactions with dark energy and dark matter fields can lead to space-time variations of fundamental constants, which can be detected through atomic spectroscopy. In this study, we examine the effects of a varying nuclear mass $m_N$ and nuclear radius $r_N$ on two transition ratios: the comparison of the two-photon transition in atomic hydrogen with the hyperfine transition in ${}^{133}\mathrm{Cs}$ based clocks, and the ratio of optical clock frequencies in ${\mathrm{Al}}^{+}$ and ${\mathrm{Hg}}^{+}$. The sensitivity of these frequency ratios to changes in $m_N$ and $r_N$ enables us to derive new limits on the variations of the proton mass, quark mass, and the QCD parameter $\theta$. Additionally, we consider the scalar field generated by the Yukawa-type interaction of feebly interacting hypothetical scalar particles with Standard Model particles in the presence of massive bodies such as the Sun and Moon. Using the data from the ${\mathrm{Al}}^{+}/{\text{Hg}}^{+}$, ${\mathrm{Yb}}^{+}/\mathrm{Cs}$, and ${\mathrm{Yb}}^{+}(\mathrm{E}2)/{\text{Yb}}^{+}(\mathrm{E}3)$ transition frequency ratios, we place constraints on the interaction of the scalar field with photons, nucleons, and electrons for a range of scalar particle masses. We also investigate limits on the Einstein equivalence principle (EEP) violating term ($c_{00}$) in the Standard Model extension (SME) Lagrangian and the dependence of fundamental constants on gravity.

Small $CPT$-violating effects are admissible in several theories beyond the Standard Model of interactions. We analyze experimental data obtained with neutral flavored meson mixing and place bounds on the scale of such phenomena. The constraints on the $CPT$-violating parameter $z$ are derived by reinterpreting the LHCb measurement of the time-dependent asymmetry in the Cabbibo-favored $D^0\to K^{-}{\pi }^{+}$ and $\overline{D^0}\to K^{+}{\pi }^{-}$ decay rates. The bounds provided in this paper are 2 orders of magnitude stricter compared to the results obtained by the FOCUS Collaboration. Among other constraints, we report bounds on the differences in the decay widths and masses of the neutral $D$ meson flavor states at a 95% confidence level. The decay width difference is bounded by $(-4.7<\delta {\mathrm{\Gamma }}_D<2.1)\times {10}^{-16}\mathrm{GeV}$. The mass difference lies within $(-2.0<\delta m_D<2.0)\times {10}^{-15}\mathrm{GeV}$ for 95% of $\arg (z)$ values. The paper includes an assessment of the influence of $CP$ violation on the results and a discussion of the future prospects.

We consider the combined measurements of $CP$-averaged decay rates and direct $CP$ asymmetries of $B^{\pm }\to K^{\pm }{\ell }^{+}{\ell }^{-}$ and $B^{\pm }\to {\pi }^{\pm }{\ell }^{+}{\ell }^{-}$ to probe (nonlocal) four-quark operator matrix element contributions to rare semileptonic $B$ meson decays. We also explore how their effects could be in principle disentangled from possible local new physics effects using $U$-spin relations. To this end, we construct a ratio of $CP$-odd decay rate differences which are exactly predicted within the standard model in the $U$-spin limit, while the leading $U$-spin breaking effects can also be systematically calculated. Our results motivate binned measurements of the direct $CP$ asymmetry in $B^{\pm }\to {\pi }^{\pm }{\ell }^{+}{\ell }^{-}$ as well as dedicated theoretical estimates of $U$-spin breaking both in local form factors as well as in four-quark matrix elements.

We revisited the computation of the cross section for the ${\mu }^{+}{\mu }^{+}\to {\ell }^{+}{\ell }^{+}$ $({\ell }^{+}={\tau }^{+},e^{+})$ transitions in the presence of new heavy Majorana neutrinos. We focus on scenarios where the masses of the new states are around some few TeV, the so-called low-scale seesaw models. Our analysis is set in a simple model with only two new heavy Majorana neutrinos considering the current limits on the heavy-light mixings. Our results illustrate the difference between the genuine effects of two nondegenerate heavy Majorana states and the degenerate case where they form a Dirac singlet field.

The nonrelativistic effective field theory (NRET) is widely used in dark matter direct detection and charged-lepton flavor violation studies through $\mu \to e$ conversion. However, existing literature has not fully considered tensor couplings. This study fills this gap by utilizing an innovative tensor decomposition method, extending NRET to incorporate previously overlooked tensor interactions. This development is expected to have a significant impact on ongoing experiments seeking physics beyond the Standard Model and on our understanding of the new-physics interactions. Notably, we identify additional operators in $\mu \to e$ conversion that are absent in scalar and vector couplings. To support further research and experimental analyses, comprehensive tables featuring tensor matrix elements and their corresponding operators are provided.

We introduce Sinyukov-like tensors, a special kind of conformal Killing tensors. In Robertson-Walker space-times, they have the perfect-fluid form and only depend on two constants and the scale factor. They are the candidates for the dark term of the newly proposed conformal Killing gravity, by Harada. In addition to ordinary matter, the Friedmann equations contain a dark term and a $\mathrm{\Lambda }$ term that parametrize the Sinyukov-like tensor. The expression of $H(z)$ is tested on cosmological data based on cosmic chronometers or including baryon acoustic oscillations. There is a large incertitude in ${\mathrm{\Omega }}_{\mathrm{\Lambda }}$ and ${\mathrm{\Omega }}_{\mathrm{dark}}$ that may become negative, but their sum is close to ${\mathrm{\Omega }}_{\mathrm{\Lambda }}$ of Lambda cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$). In any case, there is a future singularity, that is, a big rip for all positive $\mathrm{\Omega }$. We solve the equation for the evolution, in linear approximation, of the density contrast in a matter-dominated universe. The dark sector and the $\mathrm{\Lambda }$ term give no significative deviation from $\mathrm{\Lambda }\mathrm{CDM}$ and general relativity results.

Cylindrically symmetric vacuum spacetimes are of immense interest in theoretical physics due to their connection to cosmic strings hypothesized in quantum field theory. In this article, we explore the properties of such a spacetime and provide the complete, exact solution by quadrature to the timelike and lightlike geodesics in it, using the Hamilton-Jacobi formalism. In addition, we compare several properties of massive particle trajectories in relativistic cylindrically symmetric vacuum spacetimes to their nonrelativistic, Newtonian gravitational counterparts. On top of that, we devise a classification scheme and use it to categorize the orbits of massive particles.

We study the causal dynamics of an embedded null horizon foliated by marginally outer trapped surfaces (MOTS) for a locally rotationally symmetric background spacetime subjected to linear perturbations. We introduce a simple procedure which characterizes the transition of the causal character of the null horizon. We apply our characterization scheme to nondissipative perturbations of the Schwarzschild and spatially homogeneous backgrounds. For the latter, a linear equation of state was imposed. Assuming a harmonic decomposition of the linearized field equations, we clarify the variables of a formal solution to the linearized system that determine how the null horizon evolves. For both classes of backgrounds, the shear and vorticity 2-vectors are essential to the characterization, and their roles are made precise. Finally, we discuss aspects of the relationship between the characterizing conditions and the MOTS stability operator. Various properties related to the self-adjointness of the MOTS stability operator are extensively discussed.

We investigate the parity-violating scalar-tensor theory and pay special attention to terms that are free of the Ostrogradsky ghost in the unitary gauge, i.e., when the scalar field possesses a timelike gradient. We exhaustively identify the generally covariant scalar-tensor theory (GST) monomials with parity violation up to $d=4$, where $d$ is the total number of derivatives in the unitary gauge. According to the correspondence between GST terms and the spatially covariant gravity (SCG) terms in the unitary gauge, we also exhaustively identify the SCG monomials with parity violation up to $d=4$, where the Lie derivatives of the extrinsic curvature and the lapse function are necessarily introduced. We find a total of nine independent parity-violating SCG monomials, of which seven contain no higher-order Lie derivatives and are thus automatically free of ghosts, while two involve Lie derivatives of the extrinsic curvature and the lapse function and are thus potentially dangerous. By explicitly deriving their generally covariant correspondence, we obtain seven independent scalar-tensor terms dubbed the “Qi-Xiu” Lagrangians, which are the most general parity-violating scalar-tensor theories that are ghost-free in the unitary gauge up to $d=4$. Our results include the existing theories in the literature, such as the Chern-Simons term and the chiral scalar-tensor theories, as special cases.

We test deep-learning (DL) techniques for the analysis of rotational core-collapse supernovae (CCSN) gravitational-wave (GW) signals by performing classification and parameter inference of the maximum (peak) frequency and the GW strain amplitude ($\mathrm{\Delta }h$) multiplied by the luminosity distance ($D$) attained at core bounce, respectively, $(f_{\mathrm{peak}})$ and $(D·\mathrm{\Delta }h)$. Our datasets are built from a catalog of numerically generated CCSN waveforms assembled by Richers et al. 2017. Those waveforms are injected into noise from the Advanced Laser Interferometer Gravitational Wave Observatory and Advanced Virgo detectors corresponding to the O2 and O3a observing runs. For a network signal-to-noise ratio (SNR) above 5, our classification network using time series detects Galactic CCSN GW signals buried in detector noise with a false positive rate of 0.10% and a 98% accuracy, being able to detect all signals with $\mathrm{SNR}>10$. The inference of $f_{\mathrm{peak}}$ is more accurate than for $D·\mathrm{\Delta }h$, particularly for our datasets with the shortest time window (0.25 s) and for a minimum $\mathrm{SNR}=15$. From the calibration plots of predicted versus true values of the two parameters, the standard deviation ($\sigma$) and the slope deviation with respect to the ideal value are computed. We find ${\sigma }_{D·\mathrm{\Delta }h}=52.6\mathrm{cm}$ and ${\sigma }_{f_{\mathrm{peak}}}=18.3\mathrm{Hz}$, with respective slope deviations of 11.6% and 8.3%. Our best model is also tested on waveforms from a recent CCSN catalog built by Mitra et al. 2023, different from the one used for the training. For these new waveforms, the true values of the two parameters are mostly within the $1\sigma$ band around the network’s predicted values. Our results show that DL techniques hold promise to infer physical parameters of Galactic rotational CCSN events.

It has recently been conjectured [ , Phys. Rev. Lett. 133, 081401 (2024)] that there exists a correspondence between the critical threshold of black-hole formation and the stability properties of null circular geodesics in the curved spacetime of the collapsing matter configuration. In the present compact paper we provide a nontrivial test of this intriguing conjecture. In particular, using analytical techniques we study the physical and mathematical properties of self-gravitating scalar field configurations that possess marginally stable (degenerate) null circular geodesics. We reveal the interesting fact that the analytically calculated critical compactness parameter ${\mathcal{C}}^{\text{analytical}}\equiv {\max }_r\{m(r)/r\}=6/25$, which signals the appearance of the first (marginally stable) null circular geodesic in the curved spacetime of the self-gravitating scalar fields, agrees quite well (to within $\sim 10\%$) with the exact compactness parameter ${\mathcal{C}}^{\text{numerical}}\equiv {\max }_t\{{\max }_r\{m(r)/r\}\}\simeq 0.265$ which is computed numerically using fully nonlinear numerical simulations of the gravitational collapse of scalar fields at the threshold of black-hole formation [here $m(r)$ is the gravitational mass contained within a sphere of radius $r$].

Using the multipolar post-Minkowskian formalism, we compute the frequency-domain waveform generated by the gravitational scattering of two nonspinning bodies at the fourth post-Minkowskian order ($O(G^4)$, or two-loop order), and at the fractional second post-Newtonian accuracy [$O(v^4/c^4)$]. The waveform is decomposed in spin-weighted spherical harmonics and the needed radiative multipoles, $U_{\ell m}(\omega ),V_{\ell m}(\omega )$, are explicitly expressed in terms of a small number of master integrals. The basis of master integrals contains both (modified) Bessel functions, and solutions of inhomogeneous Bessel equations with Bessel-function sources. We show how to express the latter in terms of Meijer G functions. The low-frequency expansion of our results is checked against existing classical soft theorems. We also complete our previous results on the $O(G^2)$ bremsstrahlung waveform by computing the $O(G^3)$ spectral densities of radiated energy and momentum, in the rest frame of one body, at the thirtieth order in velocity.

Since galaxy distribution reconstruction effectively reduces non-Gaussian terms in the power spectrum covariance matrix, it has attracted interest not only for baryon acoustic oscillation (BAO) signals but also for various cosmological signal analyses. To this end, this paper presents a novel theoretical model that addresses infrared (IR) effects in the postreconstruction galaxy power spectrum, including one-loop corrections. In particular, we discuss the importance of incorporating nonperturbative effects arising from IR contributions into the displacement vector $\mathit{s}$ used for reconstruction. Consequently, postreconstruction nonlinear damping of BAO can be described by a single two-dimensional Gaussian function. This is a phenomenon not observed when $\mathit{s}$ is considered at a linear order in the Zel’dovich approximation. Furthermore, we confirm that the cross-power spectrum of the pre- and postreconstruction density fluctuations lacks IR effect cancellations, and shows an exponential decay in both the cross-power spectrum and the associated shot-noise term.

We present a comprehensive reassessment of the state of interacting dark energy (DE) cosmology, namely models featuring a nongravitational interaction between dark matter and DE. To achieve high generality, we extend the dark sector physics by considering two different scenarios: a nondynamical DE equation of state $w_0\ne -1$, and a dynamical $w(a)=w_0+w_a(1-a)$. In both cases, we distinguish two different physical regimes resulting from a phantom or quintessence equation of state. To circumvent early time superhorizon instabilities, the energy-momentum transfer should occur in opposing directions within the two regimes, resulting in distinct phenomenological outcomes. We study quintessence and phantom nondynamical and dynamical models in light of two independent cosmic microwave background (CMB) experiments—the Planck satellite and the Atacama Cosmology Telescope. We analyze CMB data both independently and in combination with supernovae distance moduli measurements from the Pantheon-Plus catalog and baryon acoustic oscillations from the SDSS-IV eBOSS survey. Our results update and extend the state-of-the-art analyses, significantly narrowing the parameter space allowed for these models and limiting their overall ability to reconcile cosmological tensions. Although considering different combinations of data leaves some freedom to increase $H_0$ towards the value measured by the SH0ES collaboration, our most constraining dataset ($\mathrm{CMB}+\mathrm{baryon}$ acoustic $\mathrm{oscillations}+\mathrm{supernovae}$) indicates that fully reconciling the tension solely within the framework of interacting DE remains challenging.

Recent pulsar timing array (PTA) collaborations show strong evidence for a stochastic gravitational wave background (SGWB) with the characteristic Hellings-Downs interpulsar correlations. The signal may stem from supermassive black hole binary mergers, or early Universe phenomena. The former is expected to be strongly anisotropic, while primordial backgrounds are likely to be predominantly isotropic with small fluctuations. In the case the observed SGWB is of cosmological origin, our relative motion with respect to the SGWB rest frame is a guaranteed source of anisotropy, leading to $\mathcal{O}({10}^{-3})$ energy density fluctuations of the SGWB. For such cosmological SGWB, kinematic anisotropies are likely to be larger than the intrinsic anisotropies, akin to the cosmic microwave background (CMB) dipole anisotropy. We assess the sensitivity of current PTA data to the kinematic dipole anisotropy, and we also forecast at what extent the magnitude and direction of the kinematic dipole can be measured in the future with an SKA-like experiment. We also discuss how the spectral shape of the SGWB and the location of the pulsars to monitor affect the prospects of detecting the kinematic dipole with PTA. In the future, a detection of this anisotropy may even help resolve the discrepancy in the magnitude of the kinematic dipole as measured by CMB and large-scale structure observations.

Pulsar timing array (PTA) observations hinted towards the existence of a stochastic gravitational wave background (SGWB) in the nHz frequency band. Still, the nature of the SGWB signal cannot be confidently inferred from current data, and the leading explanation invokes mergers of supermassive black holes. If confirmed, such discovery would not only represent a turning point in our understanding of astrophysics, but it may severely limit the capability of searching for additional cosmological sources in the nHz frequency range. In this work, we build a simple framework to forecast the sensitivity of future pulsar timing array configurations and assess the parameter estimation of SGWB, which could consist of several contributions. We release the python code fastpta, implementing this framework and ready to use.