We introduce consideration of a new factor, synchronization of spacetime mixmaster oscillations, that may play a simplifying role in understanding the nature of the general inhomogeneous cosmological solution to Einstein’s equations. We conjecture that, on approach to a singularity, the interaction of spacetime mixmaster oscillations in different regions of an inhomogeneous universe can produce a synchronization of these oscillations through a coupling to their mean field in the way first demonstrated by the Kuramoto coupled oscillator model.

Gravitational waves (GWs) from presumed binary black hole mergers are now being detected on a regular basis with the Advanced LIGO and Advanced Virgo interferometers. Exotic compact objects (ECOs) have been proposed that differ from Kerr black holes, and which could leave an imprint upon the GW signal in a variety of ways. Here we consider excitations of ECOs during inspiral, which may occur when the monotonically increasing GW frequency matches a resonant frequency of an exotic object. This causes orbital energy to be taken away, leading to a speed-up of the orbital phase evolution. We show that resonances with induced phase shifts $\lesssim 10$ radians can be detectable with second-generation interferometers, using Bayesian model selection. We apply our methodology to detections in the GWTC-1 catalog from the first and second observing runs of Advanced LIGO and Advanced Virgo, finding consistency with the binary black hole nature of the sources.

We calculate energy carried by a massless spin-2 field using Fierz-Lanczos representation of the theory. For this purpose Hamiltonian formulation of the field dynamics is thoroughly analyzed. Final expression for the energy is very much analogous to the Maxwell energy in electrodynamics (spin-1 field) and displays the locality property. This quantity, known as a “superenergy” in gravity theory, differs considerably from the well understood gravitational field energy (represented in linear gravity by the quadratic term in Taylor expansion of the Arnowitt-Deser-Misner energy) which cannot be localized.

We construct hybrid binary black holes merger waveforms using analytical model waveforms for the early inspiral phase and numerical relativity waveforms for late inspiral to merger and post merger phases. To hybridize analytical and numerical waveforms, we first perform a 3-dimensional rotation to align the instantaneous orbital planes associated with the two waveforms at some fiducial frequency; we then find appropriate phase and time translations that maximize the overlap of the two waveforms in a hybridization interval. We discuss the accuracy and limitations for hybrids constructed by this procedure in the context of LIGO-Virgo-KAGRA observations. Our goal is to hybridize waveforms for more generic precessing binaries and construct longer waveforms that are sufficiently accurate for the parameter estimation techniques for upcoming LIGO observations.

It has been found that the primordial non-Gaussianity of the curvature perturbation in the case of non-Bunch-Davies initial states can be enhanced compared with those in the case of the Bunch-Davies one due to the interactions among the perturbations on subhorizon scales. The purpose of the present paper is to investigate whether tensor non-Gaussianities can also be enhanced or not by the same mechanism. We consider general gravity theory in the presence of an inflaton, and evaluate the tensor auto-bispectrum and the cross-bispectrum involving one tensor and two scalar modes with the non-Bunch-Davies initial states for tensor modes. The crucial difference from the case of the scalar auto-bispectrum is that the tensor three-point function vanishes at the flattened momentum triangles. We point out that the cross-bispectrum can potentially be enhanced at nontrivial triangle shapes due to the non-Bunch-Davies initial states.

The stability of “visible” electroweak-type cosmic strings is investigated in an extension of the Standard Model by a minimal dark sector, consisting of a $U(1)$ gauge field, broken spontaneously by a scalar. The visible and dark sectors are coupled through a Higgs-portal and a gauge-kinetic mixing term. It is found that strings whose core is “filled” with a dark scalar condensate exhibit better stability properties than their analogues in the Standard Model, when the electroweak mixing angle is close to ${\theta }_W=\pi /2$. They become unstable as one lets ${\theta }_W$ approach its physical value. The instability mechanism appears to be a $W$-boson condensation mechanism found in previous studies on the stability of electroweak strings.

In order to perform Bayesian parameter estimation to infer the source properties of gravitational waves from compact binary coalescences (CBCs), the noise characteristics of the detector must be understood. It is typically assumed that the detector noise is stationary and Gaussian, characterized by a power spectral density (PSD) that is measured with infinite precision. We present a new method to incorporate the uncertainty in the power spectral density estimation into the Bayesian inference of the binary source parameters and apply it to the first 11 CBC detections reported by the LIGO-Virgo Collaboration. We find that incorporating the PSD uncertainty only leads to variations in the positions and widths of the binary parameter posteriors on the order of a few percent.

The local distance ladder measurement of the Hubble constant requires a connection between geometric distances at low redshift and Type Ia supernovae in the Hubble flow, which may be achieved through either the Cepheid period–luminosity relation or the luminosity of the tip of the Red Giant branch (TRGB) feature of the Hertzsprung–Russell diagram. Any potential solution to the Hubble tension that works by altering the distance ladder must produce consistency of both the Cepheid and TRGB $H_0$ calibrations with the CMB. In this paper we extend our models of screened fifth forces [H. Desmond, B. Jain, and J. Sakstein, Phys. Rev. D 100, 043537 (2019)] to cover the TRGB framework. A fifth force lowers TRGB luminosity, so a reduction in inferred $H_0$ requires that the stars that calibrate the luminosity—currently in the LMC—are on average less screened than those that calibrate the supernova magnitude. We show that even under pessimistic assumptions for the extinction to the LMC, full consistency with Planck can be achieved for a fifth force strength in unscreened RGB stars $\sim 0.2$ that of Newtonian gravity. This is allowed by the comparison of Cepheid and TRGB distance measurements to nearby galaxies. Our results indicate that the framework of [H. Desmond, B. Jain, and J. Sakstein, Phys. Rev. D 100, 043537 (2019)] is more versatile than initially demonstrated, capable of ameliorating the Hubble tension on a second front.

The sensitivity of wide-parameter-space searches for continuous gravitational waves is limited by computational cost. Recently it was shown that deep neural networks (DNNs) can perform all-sky searches directly on (single-detector) strain data [C. Dreissigacker , Phys. Rev. D 100, 044009 (2019)], potentially providing a low-computing-cost search method that could lead to a better overall sensitivity. Here we expand on this study in two respects: (i) using (simulated) strain data from two detectors simultaneously, and (ii) training for directed (i.e., single sky-position) searches in addition to all-sky searches. For a data time span of $T=10^5\mathrm{s}$, the all-sky two-detector DNN is about 7% less sensitive (in amplitude $h_0$) at low frequency ($f=20\mathrm{Hz}$), and about 51% less sensitive at high frequency ($f=1000\mathrm{Hz}$) compared to fully-coherent matched-filtering (using weave). In the directed case the sensitivity gap compared to matched-filtering ranges from about 7%–14% at $f=20\mathrm{Hz}$ to about 37%–49% at $f=1500\mathrm{Hz}$. Furthermore we assess the DNN’s ability to generalize in signal frequency, spin down and sky-position, and we test its robustness to realistic data conditions, namely gaps in the data and using real LIGO detector noise. We find that the DNN performance is not adversely affected by gaps in the test data or by using a relatively undisturbed band of LIGO detector data instead of Gaussian noise. However, when using a more disturbed LIGO band for the tests, the DNN’s detection performance is substantially degraded due to the increase in false alarms, as expected.

The worldwide advanced gravitational-wave (GW) detector network has so far primarily consisted of the two Advanced LIGO observatories at Hanford and Livingston, with Advanced Virgo joining the 2016-7 O2 observation run at a relatively late stage. However Virgo has been observing alongside the LIGO detectors since the start of the O3 run; in the near future, the KAGRA detector will join the global network and a further LIGO detector in India is under construction. Gravitational-wave search methods would therefore benefit from the ability to analyse data from an arbitrary network of detectors. In this paper, we extend the PyCBC offline compact binary coalescence (CBC) search analysis to three or more detectors, and describe resulting updates to the coincident search and event ranking statistic. For a three-detector network, our improved multi-detector search finds 23% more simulated signals at fixed false alarm rate in idealized colored Gaussian noise, and up to 40% more in real data, compared to the two-detector analysis previously used during O2.

We use the latest solution of the ephemeris INPOP (19a) in order to improve our previous constraint on the existence of a Yukawa suppression to the Newtonian potential, generically associated to a graviton’s mass. Unlike the ephemeris INPOP17a, several residuals are found to degrade significantly at roughly the same amplitudes of the Compton wavelength ${\lambda }_g$. As a consequence, we introduce a novel statistical criterion in order to derive the constraint with INPOP19a. After checking that it leads to a constraint consistent with our previous result when applied on INPOP17b, we apply the method to the new solution INPOP19a. We show that the residuals of Mars orbiters, Cassini, Messenger, and Juno, degrade significantly when ${\lambda }_g\le 3.43\times {10}^{13}\mathrm{km}$ with a 99.7% confidence level—corresponding to a graviton mass bigger than $3.62\times {10}^{-23}\mathrm{eV}/c^2$. This is a stronger constraint on the Compton wavelength than the one obtained from the first gravitational-wave transient catalog by the LIGO-Virgo Collaboration in the radiative regime, since our 90% C.L. limit reads ${\lambda }_g>3.93\times {10}^{13}\mathrm{km}$ ($m_g<3.16\times {10}^{-23}\mathrm{eV}/c^2$).

We show that the on-shell effective theory (OSEFT) is the quantum field theory counterpart of a Foldy-Wouthuysen diagonalization of relativistic quantum mechanics for massless fermions. Thus, it is free of the Zitterbewegung oscillations that would yield an ill-defined meaning to the semiclassical transport approach at short distances if derived from the pure Dirac picture. We present a detailed derivation of the collision terms in the chiral kinetic theory using the OSEFT. Collision integrals are derived up to order $1/E$, where $E$ is the energy of an on-shell fermion. At this order, the collision terms depend on the spin tensor of the fermion, and in the presence of chiral imbalance, it describes how a massless fermion of a given helicity interacts differently with the transverse photons of different circular polarization. In order to back up our results, we check that they allow us to reproduce the fermion decay rate in an ultradegenerate plasma with a chiral imbalance computed directly from QED.

The $\mu \text{−}\tau$ exchange symmetry in the neutrino mass matrix and its breaking as a perturbation are discussed. The exact $\mu \text{−}\tau$ symmetry restricts the 2-3 and 1-3 neutrino mixing angles as ${\theta }_{23}=\pi /4$ and ${\theta }_{13}=0$ at a zeroth-order level. We claim that the $\mu \text{−}\tau$ symmetry breaking prefers a large $CP$ violation to realize the observed value of ${\theta }_{13}$ and to keep ${\theta }_{23}$ nearly maximal, though an artificial choice of the $\mu \text{−}\tau$ breaking can tune ${\theta }_{23}$, irrespective of the $CP$ phase. We exhibit several relations among the deviation of ${\theta }_{23}$ from $\pi /4$, ${\theta }_{13}$, and the Dirac $CP$ phase $\delta$, which are useful to test the $\mu \text{−}\tau$ breaking models in near-future experiments. We also propose a concrete model to break the $\mu \text{−}\tau$ exchange symmetry spontaneously, and its breaking is mediated by the gauge interactions radiatively in the framework of the extended gauge model with $B-L$ and $L_{\mu }-L_{\tau }$ symmetries. As a result of the gauge-mediated $\mu \text{−}\tau$ breaking in the neutrino mass matrix, the artificial choice is unlikely, and a large Dirac $CP$ phase is preferable.

We scrutinize the novel chiral transport phenomenon driven by spacetime torsion, namely, the chiral torsional effect (CTE). We calculate the torsion-induced chiral currents with finite temperature, density, and curvature in the most general torsional gravity theory. The conclusion complements the previous study on the CTE by including curvature and substantiates the relation between the CTE and the Nieh-Yan anomaly. We also analyze the response of chiral torsional current to an external electromagnetic field. The resulting topological current is analogous to that in the axion electrodynamics.

Dual representations are constructed for non-Abelian lattice spin models with $U(N)$ and $SU(N)$ symmetry groups, for all $N$ and in any dimension. These models are usually related to the effective models describing the interaction between Polyakov loops in the strong coupled QCD. The original spin degrees of freedom are explicitly integrated out and a dual theory appears to be a local theory for the dual integer-valued variables. The construction is performed for the partition function and for the most general correlation function. The latter include the two-point function corresponding to quark–anti-quark free energy and the $N$-point function related to the free energy of a baryon. We consider both pure gauge models and models with static fermion determinant for both the staggered and Wilson fermions with an arbitrary number of flavours. While the Boltzmann weights of such models are complex in the presence of nonzero chemical potential the dual Boltzmann weights appear to be strictly positive on admissible configurations. An essential part of this work with respect to previous studies is an extension of the dual representation to the case of (1) an arbitrary value of the temporal coupling constant in the Wilson action and (2) an arbitrary number of flavors of static quark determinants. The applications and extensions of the results are discussed in detail. In particular, we outline a possible approach to Monte-Carlo simulations of the dual theory, to the large N expansion and to the development of a tensor renormalization group.

A symmetry-preserving continuum approach to meson bound states in quantum field theory, employed elsewhere to describe numerous $\pi$- and $K$-meson electroweak processes, is used to analyze leptonic and semileptonic decays of $D_{(s)}$ mesons. Each semileptonic transition is conventionally characterized by the value of the dominant form factor at $t=0$ and the following results are obtained herein: $f_{+}^{D_s\to K}(0)=0.673(40)$; $f_{+}^{D\to \pi }(0)=0.618(31)$ and $f_{+}^{D\to K}(0)=0.756(36)$. Working with the computed $t$-dependence of these form factors and standard averaged values for $|V_{cd}|$, $|V_{cs}|$, one arrives at the following predictions for the associated branching fractions: ${\mathcal{B}}_{D_s^{+}\to K^0{e}^{+}{\nu }_e}=3.31(33)\times {10}^{-3}$, ${\mathcal{B}}_{D^0\to {\pi }^{-}{e}^{+}{\nu }_e}=2.73(22)\times {10}^{-3}$, and ${\mathcal{B}}_{D^0\to K^{-}{e}^{+}{\nu }_e}=3.83(28)\%.$ Alternatively, using the calculated $t$-dependence, agreement with contemporary empirical results for these branching fractions requires $|V_{cd}|=0.221(9)$, $|V_{us}|=0.953(34)$. With all $D_{(s)}$ transition form factors in hand, the nature of SU(3)-flavor symmetry breaking in this array of processes can be analysed; and just as in the $\pi \text{−}K$ sector, the magnitude of such effects is found to be determined by the scales associated with emergent mass generation in the Standard Model, not those originating with the Higgs mechanism.

Heavy fermion pair production in $e^{+}{e}^{-}$ annihilation is a fundamental process in hadron physics and is of considerable interest for various phenomena. In this paper, we will apply the principle of maximum conformality (PMC) to provide a comprehensive analysis of these processes. The PMC provides a systematic, unambiguous method for determining the renormalization scales of the QCD coupling constant for single-scale and multiple-scale applications. The resulting predictions eliminate any renormalization scheme-and-scale ambiguities, eliminate the factorial renormalon divergences, and are consistent with the requirements of the renormalization group. It is remarkable that two distinctly different scales are determined by using the PMC for heavy fermion pair production near the threshold region. One scale is the order of the fermion mass $m_f$, which enters the hard virtual corrections, and the other scale is of order $v{m}_f$, where $v$ is the quark velocity, which enters the Coulomb rescattering amplitude. The PMC scales yield the correct physical behavior and reflect the virtuality of the propagating gluons (photons) for the QCD (QED) processes. Moreover, we demonstrate the consistency of PMC scale setting from QCD to QED. Perfect agreement between the Abelian unambiguous Gell-Mann-Low and the PMC scale-setting methods in the limit of zero number of colors is demonstrated.

The mass spectra of singly charmed and bottom baryons, ${\mathrm{\Lambda }}_{c/b}(1/2^{\pm },3/2^{-})$ and ${\mathrm{\Xi }}_{c/b}(1/2^{\pm },3/2^{-})$, are investigated using a nonrelativistic potential model with a heavy quark and a light diquark. The masses of the scalar and pseudoscalar diquarks are taken from a chiral effective theory. The effect of $U_A(1)$ anomaly induces an inverse hierarchy between the masses of strange and nonstrange pseudoscalar diquarks, which leads to a similar inverse mass ordering in $\rho$-mode excitations of singly heavy baryons.

We study tensor meson photoproduction outside of the resonance region, at beam energies of a few GeVs. We build a model based on Regge theory that includes the leading vector and axial exchanges. We consider two determinations of the unknown helicity couplings and fit to the recent $a_2$ photoproduction data from CLAS. Both choices give a similar description of the $a_2$ cross section but result in different predictions for the parity asymmetries and the $f_2$ photoproduction cross section. We conclude that new measurements of $f_2$ photoproduction in the forward region are needed to pin down the correct production mechanism. We also extend our predictions to the 8.5 GeV beam energy, where current experiments are running.

We present the results of the first Dalitz plot analysis of the decay $D^0\to K^{-}{\pi }^{+}\eta$. The analysis is performed on a data set corresponding to an integrated luminosity of $953{\mathrm{fb}}^{-1}$ collected by the Belle detector at the asymmetric-energy $e^{+}{e}^{-}$ KEKB collider. The Dalitz plot is well described by a combination of the six resonant decay channels ${\overline{K}}^{*}(892{)}^0\eta$, $K^{-}{a}_0(980{)}^{+}$, $K^{-}{a}_2(1320{)}^{+}$, ${\overline{K}}^{*}(1410{)}^0\eta$, $K^{*}(1680{)}^{-}{\pi }^{+}$ and $K_2^{*}(1980{)}^{-}{\pi }^{+}$, together with $K\pi$ and $K\eta$ S-wave components. The decays $K^{*}(1680{)}^{-}\to K^{-}\eta$ and $K_2^{*}(1980{)}^{-}\to K^{-}\eta$ are observed for the first time. We measure ratio of the branching fractions, $\frac{\mathcal{B}(D^0\to K^{-}{\pi }^{+}\eta )}{\mathcal{B}(D^0\to K^{-}{\pi }^{+})}=0.500\pm 0.002(\mathrm{stat})\pm 0.020(\mathrm{syst})\pm 0.003({\mathcal{B}}_{\mathrm{PDG}})$. Using the Dalitz fit result, the ratio $\frac{\mathcal{B}(K^{*}(1680)\to K\eta )}{\mathcal{B}(K^{*}(1680)\to K\pi )}$ is measured to be $0.11\pm 0.02{(\mathrm{stat})}_{-0.04}^{+0.06}(\mathrm{syst})\pm 0.04({\mathcal{B}}_{\mathrm{PDG}})$; this is much lower than the theoretical expectations ($\approx 1$) made under the assumption that $K^{*}(1680)$ is a pure $1^3{D}_1$ state. The product branching fraction $\mathcal{B}(D^0\to [K_2^{*}(1980{)}^{-}\to K^{-}\eta ]{\pi }^{+})=(2.2_{-1.9}^{+1.7})\times {10}^{-4}$ is determined. In addition, the $\pi {\eta }^{\prime }$ contribution to the $a_0(980{)}^{\pm }$ resonance shape is confirmed with $10.1\sigma$ statistical significance using the three-channel Flatté model. We also measure $\mathcal{B}(D^0\to {\overline{K}}^{*}(892{)}^0\eta )=(1.41_{-0.12}^{+0.13})\%$. This is consistent with, and more precise than, the current world average $(1.02\pm 0.30)\%$, deviates with a significance of more than $3\sigma$ from the theoretical predictions of (0.51–0.92)%.