We describe a new form of retrocausality, which is found in the behavior of a class of causal set theories, called energetic causal sets (ECS). These are discrete sets of events, connected by causal relations. They have three orders: (1) a birth order, which is the order in which events are generated; this is a total order which is the true causal order, (2) a dynamical partial order, which prescribes the flows of energy and momentum among events, (3) an emergent causal order, which is defined by the geometry of an emergent Minkowski spacetime, in which the events of the causal sets are embedded. However, the embedding of the events in the emergent Minkowski spacetime may preserve neither the true causal order in (1) nor correspond completely with the microscopic partial order in (2). We call this disordered causality, and we here demonstrate its occurrence in specific ECS models. This is the second in a series of papers centered around the question: should we accept violations of causality as a lesser price to pay in order to keep realist formulations of quantum theory? We begin to address this in the first paper [E. Cohen, M. Cortês, A. C. Elitzur, and L. Smolin, preceding paper, Realism and causality. I. Pilot wave and retrocausal models as possible facilitators, Phys. Rev. D 102, 124027 (2020).] and continue here by giving an explicit example of an ECS model in the classical regime, in which causality is disordered.

Of all basic principles of classical physics, realism should arguably be the last to be given up when seeking a better interpretation of quantum mechanics. We examine the de Broglie-Bohm pilot wave theory as a well-developed example of a realistic theory. We present three challenges to a naive reading of pilot wave theory, each based on a system of several entangled particles. With the help of a coarse graining of pilot wave theory into a discrete system, we show how these challenges can be answered. However, this comes with a cost. In the description of individual systems, particles appear to scatter off empty branches of the wave function as if they were particles and conversely travel through particles as if they were waves. More generally, the “particles” of pilot wave theory are led by the guidance equation to move in ways no classical particle would, involving apparent violations of the principles of inertia and momentum conservation. We next argue that the aforementioned cost can be avoided within a retrocausal model. In the proposed version of the pilot wave theory, the particle is guided by a combination of advanced and retarded waves. The resulting account for quantum physics seems to have greater heuristic power, demands less damage to intuition, and moreover provides some general hints regarding spacetime and causality. This is the first of two papers. In the second [E. Cohen, M. Cortês, A. C. Elitzur, and L. Smolin, Realism and causality. II. Retrocausality in energetic causal sets, Phys. Rev. D 102, 124028 (2020).], we show that, in the context of an explicit model, retrocausality, with respect to an effective, emergent spacetime metric, can coexist with a strict irreversibility of causal processes.

We obtain analytic approximate black hole solutions for higher derivative gravity in the presence of Maxwell electromagnetic sources. We construct near horizon and asymptotic solutions and then use these to obtain an approximate analytic solution using a continued fraction method to get a complete solution. We compute the thermodynamic quantities and check the first law and Smarr formula. Finally, we investigate the null and timelike geodesics of these black holes.

Using the Effective Field Theory approach together with the boundary-to-bound map, we compute the next-to-leading order (NLO) post-Minkowskian (PM) tidal effects in the conservative dynamics of compact binary systems. We derive the mass and current quadrupole and, for the first time, octupole corrections to the binding energy for circular orbits at $\mathcal{O}(G^3)$. Our results are consistent with the test-body limit as well as the existent post-Newtonian literature. We also reconstruct a Hamiltonian incorporating tidal effects to NLO in the PM expansion and find complete agreement with the recent derivation of its quadrupolar part using the classical limit of scattering amplitudes.

The canonical acoustic dark energy model (cADE), which is based on a scalar field with a canonical kinetic term that rapidly converts potential to kinetic energy around matter radiation equality, alleviates the Hubble tension found in $\mathrm{\Lambda }\mathrm{CDM}$. We show that it successfully passes new consistency tests in the cosmic microwave background (CMB) damping tail provided by the ACT data, while being increasingly constrained and distinguished from alternate mechanisms by the improved CMB acoustic polarization data from $Planck$. The best fit cADE model to a suite of cosmological observations, including the SH0ES $H_0$ measurement, has $H_0=70.25$ compared with $68.23(\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1})$ in $\mathrm{\Lambda }\mathrm{CDM}$ and a finite cADE component is preferred at the $2.8\sigma$ level. The ability to raise $H_0$ is now mainly constrained by the improved $Planck$ acoustic polarization data, which also plays a crucial role in distinguishing cADE from the wider class of early dark energy models. Atacama Cosmology Telescope and $Planck$ TE polarization data are currently mildly discrepant in normalization and drive correspondingly different preferences in parameters. Improved constraints on intermediate scale polarization approaching the cosmic variance limit will be an incisive test of the acoustic dynamics of these models and their alternatives.

In this paper, we present a careful study on the impact of neutrino pair-production on core-collapse supernovae via spherically-symmetric, general-relativistic simulations of two different massive star progenitors with energy-dependent neutrino transport. We explore the impact and consequences of both the underlying microphysics and the implementation in the radiation transport algorithms on the supernova evolution, neutrino signal properties, and the explosion dynamics. We consider the two dominant neutrino pair-production processes found in supernovae, electron-positron annihilation as well as nucleon-nucleon bremsstrahlung in combination with both a simplified and a complete treatment of the processes in the radiation transport algorithms. We find that the use of the simplified prescription quantitatively impacts the neutrino signal at the 10% level and potentially the supernova dynamics, as we show for the case of a zero-metallicity, $9.6{\mathrm{M}}_{\odot }$ progenitor. We also show that the choice of nucleon-nucleon bremsstrahlung interaction can also have a quantitative impact on the neutrino signal. A self-consistent treatment with state-of-the-art microphysics is suggested for precision simulations of core collapse, however the simplified treatment explored here is both computationally less demanding and results in a qualitatively similar evolution.

Higher-order Laguerre-Gauss (LG) modes have previously been investigated as a candidate for reducing test-mass thermal noise in ground-based gravitational-wave detectors like Advanced LIGO. It has been shown however that LG modes’ fragility against mirror surface figure imperfections limits their compatibility with the current state-of-the-art test masses. In this paper we explore the alternative of using higher-order Hermite-Gauss (HG) modes for thermal noise reduction, and show that with the deliberate addition of astigmatism they are orders of magnitude more robust against mirror surface distortions than LG modes of equivalent order. We present simulations of Advanced LIGO-like arm cavities with realistic mirror figures which can support ${\mathrm{HG}}_{33}$ modes with average arm losses and contrast defects in a Fabry-Perot Michelson interferometer configuration which are well below the typical measured values in Advanced LIGO. This demonstrates that the mirror surface flatness errors will not be a limiting factor for the use of these modes in future gravitational-wave detectors.

We point out that in models of macroscopic topological defects composed of one or more scalar fields that interact with standard model fields via scalar-type couplings the back action of ambient matter on the scalar field(s) produces an environmental dependence of the fundamental constants of nature as well as spatial variations of the fundamental constants in the vicinity of dense bodies such as Earth due to the formation of a “bubblelike” defect structure surrounding the dense body. In sufficiently dense environments, spontaneous symmetry breaking may be inhibited altogether for ${\varphi }^2$ interactions, potentially delaying the cosmological production of topological defects to rather late times. We derive bounds on nontransient variations of the fundamental constants from torsion-pendulum experiments that search for equivalence-principle-violating forces, experiments comparing the frequencies of ground- and space-based atomic clocks as well as ground-based clocks at different heights in the recent Tokyo Skytree experiment, and measurements comparing atomic and molecular transition frequencies in terrestrial and low-density astrophysical environments. Our results constrain the present-day mass-energy fraction of the Universe due to a network of infinite domain walls produced shortly after the big bang nucleosynthesis or cosmic microwave background epochs to be ${\mathrm{\Omega }}_{\text{walls},0}\ll {10}^{-10}$ for the symmetron model with a ${\varphi }^4$ potential and ${\varphi }^2$ interactions, improving over cosmic microwave background quadrupolar temperature anisotropy bounds by at least 5 orders of magnitude. Our newly derived bounds on domain walls with ${\varphi }^2$ interactions via their effects of nontransient variations of the fundamental constants are significantly more stringent than previously reported clock- and cavity-based limits on passing domain walls via transient signatures (regardless of their possible degradation due to previously neglected effects of the strongly repulsive potential generated by Earth on the passing domain walls) and previous bounds from different types of nontransient signatures (by about 10 orders of magnitude for wall thicknesses comparable to the size of Earth), under the same set of assumptions.

Extending previous work on this subject, we evaluate the impact of vectorlike fermions at next-to-leading order accuracy in models with a massive vector leptoquark embedded in the $SU(4)\times SU(3{)}^{\prime }\times SU(2{)}_L\times U(1{)}_X$ gauge group. Vectorlike fermions induce new sources of flavor symmetry breaking, resulting in tree-level flavor-changing couplings for the leptoquark not present in the minimal version of the model. These, in turn, lead to a series of nonvanishing flavor-changing neutral-current amplitudes at the loop level. We systematically analyze these effects in semileptonic, dipole and $\mathrm{\Delta }F=2$ operators. The impact of these corrections in $b\to s\nu \nu$ and $b\to c\tau \nu$ observables are discussed in detail. In particular, we show that, in the parameter region providing a good fit to the $B$-physics anomalies, the model predicts a 10% to 50% enhancement of $\mathcal{B}(B\to K^{(*)}\nu \nu )$.

We continue our study of spectroscopy data for the SU(3) gauge theory with eight fundamental fermions, motivated by the effective field theory framework of dilaton chiral perturbation theory (dChPT). At leading order dChPT predicts a constant mass anomalous dimension ${\gamma }_m$, consistent with the assumed proximity of an infrared fixed point. For the relatively large fermion masses simulated by the LatKMI Collaboration, the influence of the infrared fixed point diminishes, and our fits suggest that ${\gamma }_m$ starts running. Since a complete higher-order analysis is not feasible with presently available data, we adopt a more phenomenological approach. We propose a partial extension to higher orders, which incorporates the running of ${\gamma }_m$ into the tree-level Lagrangian. We find that this extension successfully describes the full fermion-mass range of the LatKMI data, including the pion taste splittings which arise from using staggered fermions in the lattice simulations. We also investigate a more general class of dilaton potentials proposed in the literature, using both the LSD and LatKMI datasets, concluding that these data favor the form predicted by dChPT.

In the effective field theory framework the interaction between two heavy hadrons can be decomposed into a long- and a short-range piece. The long-range piece corresponds to the one-pion-exchange potential and is relatively well known. The short-range piece is given by a series of contact-range interactions with unknown couplings, which substitute the less well-known short-range dynamics. While the general structure of the short-range potential between heavy hadrons is heavily constrained from heavy-quark symmetry, the couplings are still free parameters. Here we argue that the relative strength and the sign of these couplings can be estimated from the hypothesis that they are saturated by the exchange of light mesons, in particular the vector mesons $\rho$ and $\omega$, i.e., from resonance saturation. However, we propose a novel saturation procedure that effectively removes form-factor artifacts. From this we can determine in which spin and isospin configurations the low-energy constants are most attractive for specific two-heavy-hadron systems. In general the molecular states with lower isospins and higher spins will be more attractive and thus more probable candidates to form heavy-hadron molecules. This pattern is compatible with the interpretation of the $X(3872)$ and $P_c(4312/4440/4457)$ as molecular states, but it is not applicable to states with maximum isospin like the $Z_c(3900/4020)$.

We generalize the framework of chiral effective field theory to study the interactions of the isovector $D^{*}{\overline{D}}^{(*)}$ and $B^{*}{\overline{B}}^{(*)}$ systems up to the next-to-leading order, in which the long-, mid-, and short-range force contributions as well as the $S\text{−}D$ wave mixing are incorporated. Based on the Lippmann-Schwinger equation, we fit the invariant mass distributions of the elastic channels measured by the BESIII and Belle Collaborations. Our results indicate that the four charged charmoniumlike and bottomoniumlike states $Z_c(3900)$, $Z_c(4020)$ and $Z_b(10610)$, $Z_b(10650)$ can be well identified as the $D{\overline{D}}^{*}$, $D^{*}{\overline{D}}^{*}$ and $B{\overline{B}}^{*}$, $B^{*}{\overline{B}}^{*}$ molecular resonances. The bound state explanations are vetoed in our framework. Our study favors the $Z_c$ and $Z_b$ states are the twin partners under the heavy quark symmetry.

Ten hadronic final states of the $h_c$ decays are investigated via the process $\psi (3686)\to {\pi }^0{h}_c$, using a data sample of $(448.1\pm 2.9)\times {10}^6\psi (3686)$ events collected with the BESIII detector. The decay channel $h_c\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}{\pi }^0$ is observed for the first time and has a measured significance of $6.0\sigma$. The corresponding branching fraction is determined to be $\mathcal{B}(h_c\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}{\pi }^0)=(3.3\pm 0.6\pm 0.6)\times {10}^{-3}$ (where the uncertainties are statistical and systematic, respectively). Evidence for the decays $h_c\to {\pi }^{+}{\pi }^{-}{\pi }^0\eta$ and $h_c\to K_S^0{K}^{\pm }{\pi }^{\mp }{\pi }^{+}{\pi }^{-}$ is found with a significance of $3.6\sigma$ and $3.8\sigma$, respectively. The corresponding branching fractions (and upper limits) are obtained to be $\mathcal{B}(h_c\to {\pi }^{+}{\pi }^{-}{\pi }^0\eta )=(7.2\pm 1.8\pm 1.3)\times {10}^{-3}$ $(<1.8\times {10}^{-2})$ and $\mathcal{B}(h_c\to K_S^0{K}^{\pm }{\pi }^{\mp }{\pi }^{+}{\pi }^{-})=(2.8\pm 0.9\pm 0.5)\times {10}^{-3}$ ($<4.7\times {10}^{-3}$). Upper limits on the branching fractions for the final states $h_c\to K^{+}{K}^{-}{\pi }^0$, $K^{+}{K}^{-}\eta$, $K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}\eta$, $2(K^{+}{K}^{-}){\pi }^0$, $K^{+}{K}^{-}{\pi }^0\eta$, $K_S^0{K}^{\pm }{\pi }^{\mp }$, and $p\overline{p}{\pi }^0{\pi }^0$ are determined at a confidence level of 90%.

In this paper we consider a massive vector field in the background of a space-time obtained by certain ${\mathbb{Z}}_2$ quotient of the Banados-Teitelboim-Zanelli black hole. We analyze the backreaction of the matter field on the space-time geometry up to first order in metric perturbation. The expectation value of the stress-energy tensor can be computed exactly by considering its pullback onto the covering space. Upon a suitable choice of the boundary condition on the vector field around a noncontractible cycle of the quotient manifold it is possible to obtain the average energy on a null geodesic to be negative there by resulting a traversable wormhole.

The spectra of pions—known as the pseudo-Goldstone bosons of spontaneous chiral symmetry breaking—and their relationship with the chiral and pion superfluidity phase transitions have been investigated in the framework of soft-wall AdS/QCD. We prove that pions are massless Goldstone bosons in the chiral limit even at finite temperature, which was usually considered an assumption in soft-wall models. Above $T_c$, at which the chiral condensate $⟨\overline{q}q⟩$ vanishes, the spectra of pions and scalar mesons merge, showing evidence of restored chiral symmetry at the hadronic spectrum level. Extending to finite quark mass, pion masses increase with quark mass. Further, it is more interesting to observe that the pole masses of pions decrease with temperature below $T_c$, which agrees with the analysis by Son and Stephanov [Phys. Rev. Lett. 88, 202302 (2002)]. Meanwhile, symmetry restoration above $T_c$ could be seen in the scalar and pseudoscalar meson spectra. With finite temperature and isospin chemical potential ${\mu }_I$, we show that the masses of charged pions are split. The mass of a positively charged pion ${\pi }^{+}$ decreases almost linearly to zero when ${\mu }_I$ grows to its critical value ${\mu }_I^c$, where pion condensation begins. This reveals the Goldstone nature of ${\pi }^{+}$ after the pion superfluidity transition, which is closely related to experimental observations.

The study of scattering encounters continues to provide new insights into the general relativistic two-body problem. The local-in-time conservative dynamics of an aligned-spin binary, for both unbound and bound orbits, is fully encoded in the gauge-invariant scattering-angle function, which is most naturally expressed in a post-Minkowskian (PM) expansion, and which exhibits a remarkably simple dependence on the masses of the two bodies (in terms of appropriate geometric variables). This dependence links the PM and small-mass-ratio approximations, allowing gravitational self-force results to determine new post-Newtonian (PN) information to all orders in the mass ratio. In this paper, we exploit this interplay between relativistic scattering and self-force theory to obtain the third-subleading (4.5PN) spin-orbit dynamics for generic spins, and the third-subleading (5PN) ${\mathrm{spin}}_1\text{−}{\mathrm{spin}}_2$ dynamics for aligned spins. We further implement these novel PN results in an effective-one-body framework and demonstrate the improvement in accuracy by comparing against numerical-relativity simulations.

Recent observation shows that general relativity (GR) is not valid in the strong regime. $f(R)$ gravity, where $R$ is the Ricci scalar, is regarded to be a good candidate able to cure the anomalies that appear in conventional general relativity. In this realm, we apply the equations of motion of $f(R)$ gravity to a spherically symmetric spacetime with two unknown functions and derive original black hole (BH) solutions without any constraints on the Ricci scalar as well as on the form of $f(R)$ gravity. Those solutions depend on a convolution function and are deviating from the Schwarzschild solution of the Einstein GR. These solutions are characterized by the gravitational mass of the system and the convolution function that in the asymptotic form gives extra terms that are responsible to make such BHs different from GR. Also, we show that these extra terms make the singularities of the invariants much weaker than those of the GR BH. We analyze such BHs using the trend of thermodynamics and show their consistency with well-known quantities in thermodynamics like Hawking radiation, entropy, and quasilocal energy. We also show that our BH solutions satisfy the first law of thermodynamics. Moreover, we study the stability analysis using the odd-type mode and show that all the derived BHs are stable and have radial speed equal to one. Finally, using geodesic deviations, we derive the stability conditions of these BHs.

We describe perturbation theory (PT) models of galaxy bias for applications to photometric galaxy surveys. We model the galaxy-galaxy and galaxy-matter correlation functions in configuration space and validate against measurements from mock catalogs designed for the Dark Energy Survey (DES). We find that an effective PT model with five galaxy bias parameters provides a good description of the 3D correlation functions above scales of $4\mathrm{Mpc}/h$ and $z<1$. Our tests show that at the projected precision of the DES Year 3 analysis, two of the nonlinear bias parameters can be fixed to their coevolution values, and a third (the $k^2$ term for higher derivative bias) set to zero. The agreement is typically at the 2% level over scales of interest, which is the statistical uncertainty of our simulation measurements. To achieve this level of agreement, our fiducial model requires using the full nonlinear matter power spectrum (rather than the one-loop PT one). We also measure the relationship between the nonlinear and linear bias parameters and compare them to their expected coevolution values. We use these tests to motivate the galaxy bias model and scale cuts for the cosmological analysis of the Dark Energy Survey; our conclusions are generally applicable to all photometric surveys.

We use analytic covariance matrices to carry out a full-shape analysis of the galaxy power spectrum multipoles from the Baryon Oscillation Spectroscopic Survey (BOSS). We obtain parameter estimates that agree well with those based on the sample covariance from two thousand galaxy mock catalogs, thus validating the analytic approach and providing substantial reduction in computational cost. We also highlight a number of additional advantages of analytic covariances. First, the analysis does not suffer from sampling noise, which biases the constraints and typically requires inflating parameter error bars. Second, it allows us to study convergence of the cosmological constraints when recomputing the analytic covariances to match the best-fit power spectrum, which can be done at a negligible computational cost, unlike when using mock catalogs. These effects reduce the systematic error budget of cosmological constraints, which suggests that the analytic approach may be an important tool for upcoming high-precision galaxy redshift surveys such as DESI and Euclid. Finally, we study the impact of various ingredients in the power spectrum covariance matrix and show that the non-Gaussian part, which includes the regular trispectrum and supersample covariance, has a marginal effect ($\lesssim 10\%$) on the cosmological parameter error bars. We also suggest improvements to analytic covariances that are commonly used in Fisher forecasts.

Long-term viscous neutrino-radiation hydrodynamics simulations in full general relativity are performed for a massive disk surrounding spinning stellar-mass black holes with mass $M_{\mathrm{BH}}=4$, 6, and $10M_{\odot }$ and initial dimensionless spin $\chi \approx 0.8$. The initial disk is chosen to have mass $M_{\mathrm{disk}}\approx 0.1$ or $3M_{\odot }$ as plausible models of the remnants for the merger of black hole–neutron star binaries or the stellar core collapse from a rapidly rotating progenitor, respectively. For $M_{\mathrm{disk}}\approx 0.1M_{\odot }$ with the outer disk edge initially located at $r_{\mathrm{out}}\sim 200\mathrm{km}$, we find that 15%–20% of $M_{\mathrm{disk}}$ is ejected and the average electron fraction of the ejecta is $⟨Y_e⟩=0.30–0.35$ as found in the previous study. For $M_{\mathrm{disk}}\approx 3M_{\odot }$, we find that approximately $10\%–20\%$ of $M_{\mathrm{disk}}$ is ejected for $r_{\mathrm{out}}\approx 200–1000\mathrm{km}$. In addition, the average electron fraction of the ejecta can be enhanced to $⟨Y_e⟩\gtrsim 0.4$ because the electron fraction is increased significantly during the long-term viscous expansion of the disk with high neutrino luminosity until the mass ejection sets in. Our results suggest that not heavy $r$-process elements but light trans-iron elements would be synthesized in the matter ejected from a massive torus surrounding stellar-mass black holes. We also find that the outcomes of the viscous evolution for the high-mass disk case is composed of a rapidly spinning black hole surrounded by a torus with a narrow funnel, which appears to be suitable for generating gamma-ray bursts.