We calculate conformal field theory data for the Gross-Neveu model in $2<d<4$ dimensions at the next-to-leading order in the $1/N$ expansion. In particular, we make use of the background field method to derive various conformal triangles involving the composite operator $s^2$, for the Hubbard-Stratonovich field $s$. We then apply these conformal triangles to obtain the corresponding one-pion exchange coefficients.

Extreme-mass-ratio inspirals (EMRIs) will be key sources for LISA. However, accurately extracting system parameters from a detected EMRI waveform will require self-force calculations at second order in perturbation theory, which are still in a nascent stage. One major obstacle in these calculations is the strong divergences that are encountered on the worldline of the small object. Previously, it was shown by one of us [A. Pound, Nonlinear gravitational self-force: Second-order equation of motion, Phys. Rev. D 95, 104056 (2017)] that a class of “highly regular” gauges exist in which the singularities have a qualitatively milder form, promising to enable more efficient numerical calculations. Here we derive expressions for the metric perturbation in this class of gauges, in a local expansion in powers of distance $r$ from the worldline, to sufficient order in $r$ for numerical implementation in a puncture scheme. Additionally, we use the highly regular class to rigorously derive a distributional source for the second-order field and a pointlike second-order stress-energy tensor (the Detweiler stress energy) for the small object. This makes it possible to calculate the second-order self-force using mode-sum regularization rather than the more cumbersome puncture schemes that have been necessary previously. Although motivated by EMRIs, our calculations are valid in an arbitrary vacuum background, and they may help clarify the interpretation of point masses and skeleton sources in general relativity more broadly.

Gravitational-wave signals from binary neutron-star coalescences carry information about the star’s equation of state in their tidal signatures. A major issue in the inference of the tidal parameters (or, directly, of the equation of state) is the systematic error introduced by the waveform approximants. We use a bottom-up approach based on gauge-invariant phase analysis and the Fisher information matrix to investigate waveform systematics and identify biases in parameter estimation. A mock analysis of 15 different binaries indicates that systematics in current waveform models dominate over statistical errors at signal-to-noise ratio (SNR) $\gtrsim 80$ for LIGO and Virgo at design sensitivity. This implies biases in the inference of the reduced tidal parameter that are larger than the statistical 90% credible intervals. For example, while the neutron-star radius could be constrained at the $\sim 5\%$ level at SNR 80, systematics can be at the $\sim 10\%$ level. We apply our approach to GW170817 ($\mathrm{SNR}\sim 30$) and confirm that no significant systematic effects are present. Using frequencies below $\lesssim 1\mathrm{kHz}$ for the analysis, we estimate a neutron-star radius of ${12.5}_{-1.8}^{+1.1}\mathrm{km}$. The latter is consistent with an electromagnetic-informed prior and the recent NICER measurement. Exploring $\mathrm{SNR}\gtrsim 100$ in view of third-generation detectors, we find that all the current waveform models lead to differences of at least $1\sigma$ in the inference of the reduced tidal parameter. We conclude that current waveform models, including those from numerical relativity, are insufficient to infer the equation of state in the loudest (and potentially most informative) events that will be observed by advanced and third-generation detectors.

We consider tests of short-distance modifications of gravity based on neutron interferometry in the scenario of large extra dimensions. Avoiding the noncomputability problem in the calculation of the internal gravitational potential of extended sources, typical of models with zero-width brane, we determine the neutron optical potential associated with the higher-dimension gravitational interaction between the incident neutron and a material medium in the context of thick brane theories. Proceeding this way, we identify the physical quantity of the extra dimension model that the neutron interferometry is capable of constraining. We also consider interferometric experiments in which the phase shifter is an electric field, as in the test of the Aharonov-Casher effect. We argue that this experiment, with this nonbaryonic source, can be viewed as a test of the short-range behavior of post-Newtonian parameters that measure the capacity of the pressure and the internal energy for producing gravity.

The ringdown of a perturbed black hole contains fundamental information about space-time in the form of quasinormal modes (QNM). Modifications to general relativity, or extended profiles of other fields surrounding the black hole, so called “black hole hair”, can perturb the QNM frequencies. Previous works have examined the QNM frequencies of spherically symmetric “dirty” black holes; that is black holes surrounded by arbitrary matter fields. Such analyses were restricted to static systems, making the assumption that the metric perturbation was independent of time. However, in most physical cases such black holes will actually be growing dynamically due to accretion of the surrounding matter. Here we develop a perturbative analytic method that allows us to compute for the first time the time dependent QNM deviations of such growing dirty black holes. Whilst both are small, we show that the change in QNM frequency due to the accretion can be of the same order or larger than the change due to the static matter distribution itself, and therefore should not be neglected in such calculations. We present the case of spherically symmetric accretion of a complex scalar field as an illustrative example, but the method has the potential to be extended to more complicated cases.

It has been proven that the general relativistic Poynting-Robertson effect in the equatorial plane of the Kerr metric shows a chaotic behavior for a suitable range of parameters. As a further step, we calculate the timescale for the onset of chaos through the Lyapunov exponents, estimating how this trend impacts the observational dynamics. We conclude our analyses with a discussion on the possibility to observe this phenomenon in neutron star and black hole astrophysical sources.

The advent of stage IV weak lensing surveys will open up a new era in precision cosmology. These experiments will offer more than an order-of-magnitude leap in precision over existing surveys, and we must ensure that the accuracy of our theory matches this. Accordingly, it is necessary to explicitly evaluate the impact of the theoretical assumptions made in current analyses on upcoming surveys. One effect typically neglected in present analyses is the Doppler shift of the measured source comoving distances. Using Fisher matrices, we calculate the biases on the cosmological parameter values inferred from a Euclid-like survey, if the correction for this Doppler shift is omitted. We find that this Doppler shift can be safely neglected for stage IV surveys.

Conventional estimators of the anisotropic power spectrum and two-point correlation function (2PCF) adopt the “Yamamoto approximation,” fixing the line of sight of a pair of galaxies to that of just one of its members. While this is accurate only to first-order in the characteristic opening angle ${\theta }_{\max }$, it allows for efficient implementation via fast Fourier transforms (FFTs). This work presents practical algorithms for computing the power spectrum and 2PCF multipoles using pairwise lines of sight, adopting either the galaxy midpoint or angle bisector definitions. Using newly derived infinite series expansions for spherical harmonics and Legendre polynomials, we construct estimators accurate to arbitrary order in ${\theta }_{\max }$, though note that the midpoint and bisector formalisms themselves differ at fourth-order. Each estimator can be straightforwardly implemented using FFTs, requiring only modest additional computational cost relative to the Yamamoto approximation. We demonstrate the algorithms by applying them to a set of realistic mock galaxy catalogs, and find that both procedures produce comparable results for the 2PCF, with a slight preference for the bisector power spectrum algorithm, albeit at the cost of greater memory usage. Such estimators provide a useful method to reduce wide-angle systematics for future surveys.

We study the principal core $g$-mode oscillation in hybrid stars containing quark matter and find that they have an unusually large frequency range ($\approx 200–600\mathrm{Hz}$) compared to ordinary neutron stars or self-bound quark stars of the same mass. Theoretical arguments and numerical calculations that trace this effect to the difference in the behavior of the equilibrium and adiabatic sound speeds in the mixed phase of quarks and nucleons are provided. We propose that the sensitivity of core $g$-mode oscillations to non-nucleonic matter in neutron stars could be due to the presence of a mixed quark-nucleon phase. Based on our analysis, we conclude that for binary mergers where one or both components may be a hybrid star, the fraction of tidal energy pumped into resonant $g$-modes in hybrid stars can exceed that of a normal neutron star by a factor of 2 to 3, although resonance occurs during the last stages of inspiral. A self-bound star, on the other hand, has a much weaker tidal overlap with the $g$-mode. The cumulative tidal phase error in hybrid stars, $\mathrm{\Delta }\varphi \cong 0.5\mathrm{rad}$, is comparable to that from tides in ordinary neutron stars, presenting a challenge in distinguishing between the two cases. However, should the principal $g$-mode be excited to sufficient amplitude for detection in a postmerger remnant with quark matter in its interior, its frequency would be a possible indication for the existence of non-nucleonic matter in neutron stars.

Beyond-the-Standard-Model interactions of neutrinos among themselves—secret interactions—in the supernova core may prevent the shock revival, halting the supernova explosion. Besides, if supernova neutrinos en route to Earth undergo secret interactions with relic neutrinos, the neutrino burst reaching Earth may be down-scattered in energy, falling below the detection threshold. We probe secret neutrino interactions through supernova neutrinos and apply our findings to the supernova SN 1987A. We place the most stringent bounds on flavor-universal secret interactions occurring through a new mediator with mass between 10 MeV and 1 GeV.

The Hubble parameter inferred from cosmic microwave background observations is consistently lower than that from local measurements, which could hint towards new physics. Solutions to the Hubble tension typically require a sizable amount of extra radiation $\mathrm{\Delta }{N}_{\mathrm{eff}}$ during recombination. However, the amount of $\mathrm{\Delta }{N}_{\mathrm{eff}}$ in the early Universe is unavoidably constrained by big bang nucleosynthesis (BBN), which causes problems for such solutions. We present a possibility to evade this problem by introducing neutrino self-interactions via a simple Majoron-like coupling. The scalar is slightly heavier than 1 MeV and allowed to be fully thermalized throughout the BBN era. The rise of neutrino temperature due to the entropy transfer via $\varphi \to \nu \overline{\nu }$ reactions compensates for the effect of a large $\mathrm{\Delta }{N}_{\mathrm{eff}}$ on BBN. Values of $\mathrm{\Delta }{N}_{\mathrm{eff}}$ as large as 0.7 are in this case compatible with BBN. We perform a fit to the parameter space of the model.

An exploratory study of the timelike pion electromagnetic form factor in a Poincaré-covariant bound state formalism in the isospin symmetric limit is presented. Starting from a quark interaction kernel representing gluon-intermediated interactions for valence-type quarks, nonvalence effects are included by introducing pions as explicit degrees of freedom. The two most important qualitative aspects are, in view of the presented study, the opening of the dominant $\rho$-meson decay channel and the presence of a multiparticle branch cut setting in which the two-pion threshold is crossed. Based on a recent respective computation of the quark-photon vertex, the pion electromagnetic form factor for spacelike and timelike kinematics is calculated. The obtained results for its absolute value and its phase compare favorably to the available experimental data, and they are analyzed in detail by comparing them to the expectations based on an isospin-symmetric version of a vector-meson dominance model.

The coupling between the spin of a massive Dirac fermion and the angular momentum of the medium, i.e. the gravitomagnetic moment, is shown here to be renormalized by QED interactions at finite temperature. This means that the anomalous gravitomagnetic moment (AGM) does not vanish, and implies that thermal effects can break the Einstein equivalence principle in quantum field theory, as argued previously. We also show that the AGM causes radiative corrections to the axial current of massive fermions induced by vorticity in quantum relativistic fluids, similarly to the previous findings for massless fermions. The radiative QCD effects on the AGM should significantly affect the production of polarized hadrons in heavy-ion collisions.

A TeV spectral break in the total flux of cosmic-ray electrons and positrons (CREs) at which the spectral power index softens from $\sim 3$ to $\sim 4$ has been observed by H.E.S.S. and recently confirmed by DAMPE with a high significance of $6.6\sigma$. Such an observation is apparently inconsistent with the data from other experiments such as Fermi-LAT, AMS-02, and CALET. We perform a global analysis on the latest CRE data including Fermi-LAT, AMS-02, CALET, DAMPE, and H.E.S.S., with energy scale uncertainties taken into account to improve the consistency between the datasets. The fit result strongly favors the existence of the break at $\sim 1\mathrm{TeV}$ with an even higher statistical significance of $13.3\sigma$. In view of the tentative CRE break, we revisit a number of models of nearby sources, such as a single generic pulsar wind nebula (PWN), known multiple PWNe from the ATNF catalog, and their combinations with either an additional dark matter (DM) component or a supernova remnant (SNR). We show that the CRE break at $\sim 1\mathrm{TeV}$, together with the known CR positron excess, points towards the possibility that the nearby sources should be highly charge asymmetric. Among the models under consideration, the one with a PWN plus a SNR is the most favored by the current data. The favored distances and ages of the PWN and SNR sources are both within 0.6 kpc and around ${10}^5\mathrm{yr}$, respectively. Possible candidate sources include PSR J0954-5430, Vela and the Monogem ring, etc. We find that for the models under consideration, the additional DM component is either unnecessary or predicts too much photon emission in tension with the H.E.S.S. data of $\gamma$-rays from the direction of the Galactic Center. We also show that the current measurement of the anisotropies in the arrival direction of the CRE can be useful in determining the properties of the sources.

We consider the direct $s$-channel gravitational production of dark matter during the reheating process. Independent of the identity of the dark matter candidate or its nongravitational interactions, the gravitational process is always present and provides a minimal production mechanism. During reheating, a thermal bath is quickly generated with a maximum temperature $T_{\max }$, and the temperature decreases as the inflaton continues to decay until the energy densities of radiation and inflaton oscillations are equal, at $T_{\mathrm{RH}}$. During these oscillations, $s$-channel gravitational production of dark matter occurs. We show that the abundance of dark matter (fermionic or scalar) depends primarily on the combination $T_{\max }^4/T_{\mathrm{RH}}{M}_P^3$. We find that a sufficient density of dark matter can be produced over a wide range of dark matter masses: from 1 GeV to 1 ZeV.

In this paper, an approach for neutral Higgs boson searches is described based on 2HDM type I at electron-positron linear colliders operating at $\sqrt{s}=1\mathrm{TeV}$. The beam is assumed to be unpolarized and fast detector simulation is included. The signal process produces a fully hadronic final state through $e^{+}{e}^{-}\to AH\to b\overline{b}b\overline{b}$ where both $CP$-even and $CP$-odd Higgs bosons ($H$ and $A$) are assumed to decay to a pair of $b$-jets. Several benchmark scenarios are introduced as the baseline for the analysis taking $m_{H/A}$ in the range 150–300 GeV. In order to avoid Higgs boson conversion $A\to ZH$, Higgs boson masses are chosen with $m_A-m_H<m_Z$. It is shown that with a proper kinematic correction applied on final state $b$-jet four momenta, true combinations of $b$-jets can be found for simultaneous reconstruction of both Higgs bosons through $b\overline{b}$ invariant mass calculation. Results show that observable signals can be achieved with statistical significance exceeding $5\sigma$ well before the target integrated luminosity of $8{\mathrm{ab}}^{-1}$.

The deviations of $B$-meson decays measured in $R_{D^{(*)}}^{\tau \ell }$ and $R_{K^{(*)}}^{\mu e}$ can be explained by the presence of two scalar leptoquarks, a singlet $S_1$ and a triplet $S_3$, mostly coupled to the third generation. We consider a theory of resonances, as an effective description of a strongly interacting theory, that generates the leptoquarks and the Higgs as Nambu-Goldstone bosons, with the rest of the resonances at a scale of order 10–30 TeV. We assume anarchic partial compositeness for the flavor of the SM fermions. Under this hypothesis, we study whether it is possible to reproduce the deviations in the $B$ decays without being in conflict with flavor and electroweak bounds. We find a tension between $R_{D^{(*)}}^{\tau \ell }$ and some flavor observables, dominated by flavor violating $\tau$ decays and $\mathrm{\Delta }{m}_{B_s}$, that require a tuning of order 10%–25%. We also compute the potential of the scalars showing that leptoquarks with masses $O(2–3)\mathrm{TeV}$ can be naturally expected in the model. We discuss briefly the phenomenology of the other resonances.

We demonstrate that multiple-Higgs production at the LHC is the most sensitive probe of first- and second-generation quark flavor in the Higgs sector. In models where new scalars couple to light quarks, gigantic di-Higgs and even sizable tri-Higgs production rates can be obtained, which can be used to either discover or severely constrain such theories. As an example, we show that the most stringent bounds on enhanced interactions of the 125 GeV Higgs to the down quark in extended Higgs sectors are obtained by looking for the extra Higgs bosons that provide for such enhancements using the di-Higgs and $Zh$ topologies. In this context, we set new limits on the 125 GeV Higgs coupling to the down quark as strong as ${\lambda }_{hd\overline{d}}\lesssim 20{\lambda }_{hd\overline{d}}^{\mathrm{SM}}$—a dramatic improvement over previously available bounds. Regarding second-generation quark flavor, we obtain new limits in the coupling to strange as strong as ${\lambda }_{hs\overline{s}}\lesssim 10{\lambda }_{hs\overline{s}}^{\mathrm{SM}}$. In addition, we show that the currently unexplored triple-Higgs production topology could be a potential discovery channel of a wide variety of extended Higgs sectors at the LHC, including not only models where extra Higgses couple to light quarks, but also more frequently studied theories where they have preferential couplings to the top.

We discuss gluon-gluon mechanisms for production of mesons with hidden strangeness, such as ${\eta }^{\prime }$ and $\varphi$ meson, in proton-proton collisions at large energies. The $g^{*}{g}^{*}\to {\eta }^{\prime }$ and $g^{*}{g}^{*}\to \varphi g$ mechanisms are considered only, and the corresponding cross sections are calculated in the $k_t$-factorization approach. The $F_{{\gamma }^{*}{\gamma }^{*}\to {\eta }^{\prime }}$ and $F_{g^{*}{g}^{*}\to {\eta }^{\prime }}$ form factors are calculated from the quark-antiquark ${\eta }^{\prime }$ light-cone wave function including quark/antiquark transverse momenta. The result for the two-photon transition form factor demonstrates that higher twists may survive even to large photon virtualities. The result is compared with the result of a recent leading-twist next-to-leading-order analysis, which uses phenomenological distribution amplitudes fitted to exclusive production of ${\eta }^{\prime }$ in $e^{+}{e}^{-}\to e^{+}{e}^{-}{\eta }^{\prime }$ reaction. We calculate transverse momentum distributions of both ${\eta }^{\prime }$ and $\varphi$ mesons in proton-proton collisions for Relativistic Heavy Ion Collider and LHC energies. The results are compared to experimental data whenever available. The results of the Lund string model are shown for comparison for ${\eta }^{\prime }$ production at LHC energies. It seems that the two-gluon fusion is not the dominant mechanism for both $\varphi$ and ${\eta }^{\prime }$ production, although the situation for ${\eta }^{\prime }$, especially at larger energies, is less clear due to lack of experimental data.