Using the Schwinger-Keldysh path integral, we draw a connection between localized quantum field theories and more commonly used models of local probes in relativistic quantum information (RQI). By integrating over and then tracing out the inaccessible modes of the localized field being used as a probe, we show that, at leading order in perturbation theory, the dynamics of any finite number of modes of the probe field is exactly that of a finite number of harmonic-oscillator Unruh-DeWitt (UDW) detectors. The equivalence is valid for a rather general class of input states of the probe-target field system, as well as for any arbitrary number of modes included as detectors. The path integral also provides a closed-form expression which gives us a systematic way of obtaining the corrections to the UDW model at higher orders in perturbation theory due to the existence of the additional modes that have been traced out. This approach vindicates and extends a recently proposed bridge between detector-based and field-theory-based measurement frameworks for quantum field theory [T. R. Perche et al., Particle detectors from localized quantum field theories, Phys. Rev. D 109, 045013 (2024).], and also points to potential connections between particle detector models in RQI and other areas of physics where path integral methods are more commonplace—in particular, the Wilsonian approach to the renormalization group and effective field theories.

The presence of strong electromagnetic fields adds huge complexity to QED Feynman diagrams, such that new methods are required to calculate higher-loop and higher-multiplicity scattering amplitudes. Here we use the worldline formalism to present “master formulas” for all tree level amplitudes of two massive particles and an arbitrary number of photons, in a plane wave background, in both scalar and spinor QED. The plane wave is treated without approximation throughout, meaning in particular that our formulas are valid in the strong-field regime of current theoretical and experimental interest. We check our results against literature expressions obtainable at low multiplicity via direct Feynman diagram calculations.

The Casimir effect is induced by the interplay between photon fields and boundary conditions, and in particular, photon fields modified in axion electrodynamics may lead to the sign-flipping of the Casimir energy. We propose a theoretical approach to derive the Casimir effect in axion electrodynamics. This approach is based on a lattice regularization and enables us to discuss the dependence on the lattice spacing for the Casimir energy. With this approach, the sign-flipping behavior of the Casimir energy is correctly reproduced. By taking the continuum limit of physical quantity calculated on the lattice, we can obtain the results consistent with the continuum theory. This approach can also be applied to the Casimir effect at nonzero temperature.

We present NRPMw, an analytical model of gravitational-waves from neutron star merger remnants informed using 618 numerical relativity (NR) simulations. NRPMw is designed in the frequency domain using a combination of complex Gaussian wavelets. The wavelet’s parameters are calibrated to equations of state (EOSs) insensitive relations from NR data. The NR simulations are computed with 21 EOSs (seven of which are finite-temperature microphysical models, and three of which contain quark phase transitions or hyperonic degrees of freedom) and span total binary masses $M\in [2.4,3.4]M_{\odot }$, mass ratios up to $q=2$, and (nonprecessing) dimensionless spins magnitudes up to 0.2. The theoretical uncertainties of the EOS-insensitive relations are incorporated in NRPMw using recalibration parameters that enhance the flexibility and accuracy of the model. NRPMw is NR faithful with fitting factors $\gtrsim 0.9$ computed on an independent validation set of 102 simulations.

Solving the Einstein-Klein-Gordon-Maxwell system, we construct and analyze the properties of an electrically charged wormhole, formed from a complex, massive scalar field, with self-interaction, and endowed with an electric charge. The scalar field is minimally coupled to the gravitational and the Maxwell field. Covering regions of the value of the different parameters of such wormhole, we present the dependence of the form of the solution with respect to the value of those parameters, emphasizing the role played by the charge in the configurations; we focus on the region for large values of the self-interaction parameter and found a generic behavior of the scalar field, which in turn allows us to determine explicit analytic expressions for the fields, the metric function, and the global quantities such as the Komar mass and the particle number. The motion of charges in these spacetimes is also reported.

We propose and perform a joint analysis of the two different mass estimates of galaxy clusters, namely, the hydrostatic and caustic techniques. First, we show comprehensively that the mass bias between these two techniques can be possibly alleviated when cluster-specific assumptions constrained using the hydrostatic technique are utilized within the caustic technique. While at face value this demotes the caustic technique from a completely independent method, this allows one to further tighten the constraints on the cluster mass and, subsequently, allows us to test modifications to gravity. Implementing the aforementioned formalism for two well-observed massive galaxy clusters, A2029 and A2142, we highlight the proof of concept. In the current implementation, we use this method to constrain the chameleon and Vainshtein screening. As anticipated, we show that the joint analysis can help improve the constraints on these modified gravity scenarios.

We examine the quasinormal modes of Ellis-Bronnikov wormholes embedded in a warped five-dimensional braneworld background and compare with its four-dimensional counterpart. These scalar quasinormal frequencies are obtained using the WKB formula, Prony method, and the direct integration method. The signature of the warped extra dimension shows up as two distinct quasinormal ringing eras, characterized by two distinct dominant quasinormal modes. Features of the latter region are similar to that observed earlier for massive scalar fields in the black hole background, particularly the existence of arbitrarily long-lived quasinormal modes. We also discuss the how steepness of the neck of the wormhole effects the quasinormal frequencies.

Multiple pulsar timing array (PTA) collaborations recently announced the evidence of common-spectral processes caused by gravitational waves (GWs). These can be the stochastic GW background and its origin may be astrophysical and/or cosmological. We interpret it as the GWs induced by the primordial curvature perturbations and discuss their implications on primordial black holes (PBHs). We show that the newly released data suggest PBHs much lighter than the Sun [$\mathcal{O}({10}^{-4})M_{\odot }$ for the delta-function curvature spectrum; $<\mathcal{O}({10}^{-2})M_{\odot }$ more generally] in contrast to what was expected from the previous PTA data releases.

In this work, we investigate detection rates and parameter estimation of strongly lensed extreme mass-ratio inspirals (LEMRIs) in the context of the Laser Interferometer Space Antenna (LISA). Our results indicate that LEMRIs constitute a new gravitational-wave target signal for LISA, with detection rates ranging from zero to $\sim 40$ events over a four year-observation period, and that it is possible to reveal and characterize LEMRIs at redshift $z\gtrsim 1$. We finally show that one LEMRI observation with identified host galaxy may yield percent constraints or better on the Hubble constant.

The growth of large-scale structures, together with the geometrical information of cosmic expansion history and cosmological distances, can be used to obtain constraints on the spatial curvature of the Universe that probes the early Universe physics, whereas modeling the nonlinear growth in a nonflat universe is still challenging due to the computational expense of simulations in a high-dimensional cosmological parameter space. In this paper, we develop an approximate method to compute the halo-matter and halo-autopower spectra for nonflat $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) model, from quantities representing the nonlinear evolution of the corresponding flat $\mathrm{\Lambda }\mathrm{CDM}$ model, based on the separate universe method. By utilizing the fact that the growth response to long-wavelength fluctuations (equivalently, the curvature) $T_{{\delta }_{\mathrm{b}}}(k)$ is approximated by the response to the Hubble parameter $T_h(k)$, our method allows one to estimate the nonlinear power spectra in a nonflat universe efficiently from the power spectra of the flat universe. We use $N$-body simulations to show that the estimator can provide the halo-matter (halo-auto) power spectrum at $\sim 1\%$ ($\sim 2\%$) accuracy up to $k\simeq 3(1)h{\mathrm{Mpc}}^{-1}$ even for a model with large curvature ${\mathrm{\Omega }}_K=\pm 0.1$. Using the estimator, we can extend the prediction of the existing emulators such as dark emulator to nonflat models without degrading their accuracy. Since the response to long-wavelength fluctuations is also a key quantity for estimating the supersample covariance (SSC), we discuss that the approximate identity $T_{{\delta }_{\mathrm{b}}}(k)\approx T_h(k)$ can be used to calculate the SSC terms analytically.

The thermal Sunyaev-Zeldovich (tSZ) effect is a spectral distortion of the cosmic microwave background (CMB) resulting from inverse Compton scattering of CMB photons with electrons in the medium of galaxy clusters. The spectrum of the tSZ effect is typically calculated assuming the spectrum of the CMB is a blackbody. However, energy or photon number injection at any epoch after photon creation processes become inefficient will distort the blackbody, potentially leading to a chemical potential or $\mu$ distortion for early injection. These primordial spectral distortions will therefore introduce a change in the tSZ effect, effectively a distortion of a distortion. While this effect is small for an individual cluster’s spectrum, upcoming and proposed CMB surveys expect to detect tens of thousands of clusters with the tSZ effect. In this paper, we forecast constraints on the $\mu$-distortion monopole from the distortion of the tSZ spectrum of clusters measured by CMB surveys. We find that planned experiments have the raw sensitivity to place constraints on $\mu$ that are comparable to or better than existing constraints but control over foregrounds and other systematics will be critical.

Axionlike particles (ALPs) may undergo mixing with photons in the presence of astrophysical magnetic fields, leading to alterations in the observed high energy $\gamma$-ray spectra. In this study, we investigate the ALP-photon oscillation effect using the spectra of the blazar Mrk 421 over 15 observation periods measured by Major Atmospheric Gamma Imaging Cherenkov Telescopes (MAGIC) and Fermi Large Area Telescope (Fermi-LAT). Compared with previous studies, we generate mock data under the ALP hypothesis and employ the ${\mathrm{CL}}_{\mathrm{s}}$ method to set constraints on the ALP parameters. This method is widely utilized in high energy experiments and avoids the exclusion of specific parameter regions where distinguishing between the null and ALP hypotheses is challenging. We find that the ALP-photon coupling $g_{a\gamma }$ is constrained to be smaller than $\sim 2\times {10}^{-11}{\mathrm{GeV}}^{-1}$ for ALP masses ranging from ${10}^{-9}\mathrm{eV}$ to ${10}^{-7}\mathrm{eV}$ at the 95% confidence level. We also present the constraints derived from the TS distribution under the null hypothesis, which is commonly utilized in previous astrophysical ALP studies. Our results reveal that the combined constraints of all the periods obtained from both methods are consistent. However, the ${\mathrm{CL}}_{\mathrm{s}}$ method remains effective in cases where the latter method fails to provide constraints for specific observation periods.

In the deep learning era, improving the neural network performance in jet physics is a rewarding task, as it directly contributes to more accurate physics measurements at the LHC. Recent research has proposed various network designs in consideration of the full Lorentz symmetry, but its benefit is still not systematically asserted, given that there remain many successful networks without taking it into account. We conduct a detailed study on the Lorentz-symmetric design. We propose two generalized approaches for modifying a network—these methods are experimented on Particle Flow Network, ParticleNet, and LorentzNet and exhibit a general performance gain. We also reveal that the notable improvement attributed to the “pairwise mass” feature in the network is due to its introduction of a structure that fully complies with Lorentz symmetry. We confirm that Lorentz-symmetry preservation serves as a strong inductive bias of jet physics, hence calling for attention to such general recipes in future network designs.

We present a phenomenological extraction of transversity distribution functions and Collins fragmentation functions by simultaneously fitting to semi-inclusive deep inelastic scattering and electron-positron annihilation data. The analysis is performed within the transverse-momentum-dependent factorization formalism, and sea quark transversity distributions are taken into account for the first time. We find the $\overline{u}$ quark favors a negative transversity distribution, while that of the $\overline{d}$ quark is consistent with zero according to the current accuracy. In addition, based on a combined analysis of world data and simulated data, we quantitatively demonstrate the impact of the proposed Electron-Ion Collider in China on precise determinations of the transversity distributions, especially for sea quarks, and the Collins fragmentation functions.

The CMS and ATLAS Collaborations have recently reported their results searching for a light Higgs boson with mass around 95 GeV, based on the full run 2 dataset. In the framework of the $CP$-violating (CPV) $\mu$-from-$\nu$ supersymmetric standard model (SSM), we discuss an $\sim 2.9\sigma$ (local) excess at 95 GeV in the light Higgs boson search in the diphoton decay mode as reported by ATLAS and CMS, together with an $\sim 2\sigma$ excess (local) in the $b\overline{b}$ final state at LEP in the same mass range. By introducing CPV phases as well as by mixing $CP$-even Higgs and $CP$-odd Higgs, a lighter Higgs boson in the $\mu$-from-$\nu$ SSM can be produced, which can account for the “diphoton excess.”

In the presence of extra neutrino states at high scales, the low-energy effective $3\times 3$ leptonic mixing matrix (LMM) is in general nonunitary. We revisit the question of what is our current knowledge of individual LMM matrix elements without assuming unitarity. We first demonstrate that a minimal set of experimental constraints suffices in bounding LMM nonunitarity parameters to the level of $\mathcal{O}({10}^{-3})$, without the use of neutrino oscillation data. We then revisit oscillation results as a complementary cross-check, using different physics and different experimental techniques to probe a similar parameter space. We correct some common misconceptions in the neutrino nonunitarity literature resulting from an incautious treatment of input parameters. We find that neutrino oscillation experiments can constrain LMM nonclosure, but, contrary to claims in the literature, are completely insensitive to the overall normalization of the LMM. Thus, we conclude that oscillation experiments, including the future DUNE experiment, have no power in excluding nonunitarity altogether.

The extension of the Standard Model lepton sector by three right-handed Majorana neutrinos [heavy neutral leptons (HNLs)] with masses up to GeV scale is considered. While the lightest heavy neutral lepton is the dark matter particle with mass of the order of 5 keV, the remaining two HNLs ensure standard (active) neutrino mass generation by means of the seesaw type I mechanism. Two heavy sterile neutrinos with quasidegenerate masses up to 5 GeV can induce the deviation of lepton universality violation parameter in the decays of ${\pi }^{+}$ and $K^{+}$ mesons from the Standard Model value. Contours are obtained for the permissible values of this parameter within the framework of two mixing scenarios, taking into account the lifetime boundary for heavy neutral lepton from big bang nucleosynthesis in the Universe. When calculating the HNL decay width in the framework of the model with six Majorana neutrinos, three active and three heavy, both two-particle and three-particle lepton decays, essential for masses below the mass of the pion, were taken into account. When calculating the decay widths, the limiting case known as the “Dirac limit” is not used. The results based on the explicit form of mixing matrices for three HNL generations and the diagram technique for Majorana neutrinos, which explicitly take into account the interference terms for diagrams with identical mass states, can lead to some differences in lifetime from the results using the Dirac limit and the displacement of the corresponding experimental exclusion contours of the “mass-mixing” type. For the second mixing scenario, a mass region of $460\mathrm{MeV}<M<485\mathrm{MeV}$ has been found that allows violation of lepton universality in charged kaon decays at the level observed in the experiment.

A lattice QCD approach to the calculation of the long-distance contributions to ${\epsilon }_K$ is presented. This parameter describes indirect $CP$ violation in $K\to \pi \pi$ decay. While the short-distance contribution to ${\epsilon }_K$ can be accurately calculated in terms of standard model parameters and a single hadronic matrix element, $B_K$, there is a long-distance part which is estimated to be approximately 5% of the total and is more difficult to determine. A method for determining this small but phenomenologically important contribution to ${\epsilon }_K$ using lattice QCD is proposed and a complete exploratory calculation of the contribution is presented. This exploratory calculation uses an unphysical light quark mass corresponding to a 339 MeV pion mass and an unphysical charm quark mass of 968 MeV, expressed in the $\overline{\mathrm{MS}}$ scheme at 2 GeV. This calculation demonstrates that future work should be able to determine this long-distance contribution from first principles with a controlled error of 10% or less.

The forward-backward asymmetry of the Drell-Yan process in dilepton decays at high invariant masses can be used to probe the parton distribution functions at large $x$. The behavior of three modern parton distribution function sets (CT18NNLO, MSHT20, and NNPDF4.0) are compared, and updated under various scenarios via epump using proton-proton collision pseudodata generated at $\sqrt{s}=13\mathrm{TeV}$ with $3000{\mathrm{fb}}^{-1}$ of integrated luminosity.

We determine the masses and residues of the ground and excited spin-$\frac{1}{2}$ baryons consist of two heavy b or c quark utilizing the QCD sum rule formalism. In the calculations, we consider the nonperturbative operators up to ten mass dimensions in order to increase the accuracy compared to the previous calculations. We report the obtained results for both the symmetric and antisymmetric currents defining the doubly heavy baryons of the ground state (1S), first orbitally excited state (1P), and first radially excited state (2S). We compare our results with the predictions of other nonperturbative approaches as well as existing experimental data which is available only for the ground state of ${\mathrm{\Xi }}_{cc}$ channel. These predictions can help the experimental groups in their searches for all members of the doubly heavy baryons in their ground and exited states.