The Galactic Center GeV excess (GCE) has garnered great interest as a possible signal of either dark matter annihilation or some novel astrophysical phenomenon, such as a new population of gamma-ray emitting pulsars. In a companion paper, we showed that in a 10° radius region of interest (ROI) surrounding the Galactic Center, apparent evidence for GCE point sources (PSs) from non-Poissonian template fitting (NPTF) is actually an artifact of unmodeled north-south asymmetry of the GCE. In this work, we develop a simplified analytic description of how signal mismodeling can drive an apparent preference for a PS population, and demonstrate how the behavior pointed out in the companion paper also appears in simpler simulated datasets that contain no PS signals at all. We explore the generality of this behavior in the real gamma-ray data, and discuss the implications for past and future studies using NPTF techniques. While the drop in PS preference once north-south asymmetry is included is not ubiquitous in larger ROIs, we show that any overly-rigid signal model is expected to yield a spurious PS signal that can appear very convincing: as well as apparent significance comparable to what one would expect from a true PS population, the signal can exhibit stability against a range of variations in the analysis, and a source count function that is very consistent with previous apparent NPTF-based detections of a GCE PS population. This contrasts with previously studied forms of systematic mismodeling which are unlikely to mimic a PS population in the same way. In the light of this observation, and its explicit realization in the region where the GCE is brightest, we argue that a dominantly smooth origin for the GCE is not in tension with existing NPTF analyses.

We study the fully nonlinear fast flavor evolution of neutrinos in $1+1$ dimensions. Our numerical analysis shows that at late times, the system reaches an approximately steady state. Using the steady-state approximation, we analytically show that the spatial variation of the polarization vectors is given by their precession around a common axis, which itself has a motion reminiscent of a gyroscopic pendulum. We then show that the steady-state solution to the equations of motion cannot be separated in position and velocity—that is, the motion is not collective in the usual sense. However, the fast evolution allows spectral-swap-like dynamics leading to partial decoherence over a range of velocities, constrained by the conservation of lepton number(s). Finally, we numerically show that at late times, the transverse components of the polarization vectors become randomly oriented at different spatial locations for any velocity mode and lepton asymmetry.

Recent gamma-ray and radio observations provide stringent constraints for annihilating dark matter. The current $2\sigma$ lower limits of dark matter mass can be constrained to $\sim 100\mathrm{GeV}$ for thermal relic annihilation cross section. In this article, we use the radio continuum spectral data of a nearby galaxy NGC4214 and differentiate the thermal contribution, dark matter annihilation contribution and cosmic-ray contribution. We can get more stringent constraints of dark matter mass and annihilation cross sections. The $5\sigma$ lower limits of thermal relic annihilating dark matter mass obtained are 300 GeV, 220 GeV, 220 GeV, 500 GeV, and 600 GeV for $e^{+}{e}^{-}$, ${\mu }^{+}{\mu }^{-}$, ${\tau }^{+}{\tau }^{-}$, $W^{+}{W}^{-}$. and $b\overline{b}$ channels respectively. These limits challenge the dark matter interpretation of the gamma-ray, positron, and antiproton excess in our Milky Way.

The axion-gravity Chern-Simons coupling is well motivated but is relatively weakly constrained, partly due to difficult measurements of gravity. We study the sensitivity of LIGO measurements of chirping gravitational waves (GWs) on such coupling. When the frequency of the propagating GW matches with that of the coherent oscillation of axion dark matter field, the decay of axions into gravitons can be stimulated, resonantly enhancing the GW. Such a resonance peak can be detected at LIGO as a deviation from the chirping waveform. Since all observed GWs will undergo similar resonant enhancement from the Milky Way (MW) axion halo, LIGO $\mathrm{O}1+\mathrm{O}2$ observations can potentially provide the strongest constraint on the coupling, at least for the axion mass $m_a=5\times {10}^{-13}-5\times {10}^{-12}\mathrm{eV}$. Along the course, we also emphasize the relevance of the finite coherence of axion fields and the ansatz separating forward and backward propagations of GWs. As a result, the parity violation of the Chern-Simons coupling is not observable from chirping GWs.

We discuss a few tests of the $\mathrm{ER}=\mathrm{EPR}$ proposal. We consider certain conceptual issues as well as explicit physical examples that could be experimentally realized. In particular, we discuss the role of the Bell bounds, the large N limit, as well as the consistency of certain theoretical assumptions underlying the $\mathrm{ER}=\mathrm{EPR}$ proposal. As explicit tests of the $\mathrm{ER}=\mathrm{EPR}$ proposal we consider limits coming from the entropy-energy relation and certain limits coming from measurements of the speed of light as well as measurements of effective weights of entangled states. We also discuss various caveats of such experimental tests of the $\mathrm{ER}=\mathrm{EPR}$ proposal.

In this paper we construct the Fermi coordinates along any arbitrary line in a simple analytical way without use of orthogonal frames and their transport. In this manner we extend the Eddington approach to the construction of the Fermi metric in terms of the Riemann tensor. In the second part of the present article we show how the proposed approach works practically by applying it for deriving the Fermi coordinates for the static observer in the Schwarzschild spacetime.

In this paper, we systematically study spherically symmetric static spacetimes in the framework of Einstein-aether theory and pay particular attention to the existence of black holes (BHs). In the theory, two additional gravitational modes (one scalar and one vector) appear, due to the presence of a timelike aether field. To avoid the vacuum gravi-Čerenkov radiation, they must all propagate with speeds greater than or at least equal to the speed of light. In the spherical case, only the scalar mode is relevant, so BH horizons are defined by this mode, which are always inside or at most coincide with the metric (Killing) horizons. In the present studies, we first clarify several subtle issues. In particular, we find that, out of the five nontrivial field equations, only three are independent, so the problem is well posed, as now generically there are only three unknown functions, $F(r)$, $B(r)$, $A(r)$, where $F$ and $B$ are metric coefficients, and $A$ describes the aether field. In addition, the two second-order differential equations for $A$ and $F$ are independent of $B$, and once they are found, $B$ is given simply by an algebraic expression of $F$, $A$ and their derivatives. To simplify the problem further, we explore the symmetry of field redefinitions, and work first with the redefined metric and aether field, and then obtain the physical ones by the inverse transformations. These clarifications significantly simplify the computational labor, which is important, as the problem is highly involved mathematically. In fact, it is exactly because of these, we find various numerical BH solutions with an accuracy that is at least two orders higher than previous ones. More important, these BH solutions are the only ones that satisfy the self-consistent conditions and meantime are consistent with all the observational constraints obtained so far. The locations of universal horizons are also identified, together with several other observationally interesting quantities, such as the innermost stable circular orbits (ISCO), the ISCO frequency, and the maximum redshift $z_{\max }$ of a photon emitted by a source orbiting the ISCO. All of these quantities are found to be quite close to their relativistic limits.

In the present paper, we consider the multiscalar extension of Einstein-Gauss-Bonnet gravity. We focus on multiscalar Einstein-Gauss-Bonnet models whose target space is a three-dimensional maximally symmetric space, namely, either ${\mathbb{S}}^3$, ${\mathbb{H}}^3$, or ${\mathbb{R}}^3$, and in the case in which the map $\mathit{\text{spacetime}}\to \mathit{\text{target space}}$ is nontrivial. We prove numerically the existence of black holes in this class of models for several Gauss-Bonnet coupling functions, including the case of scalarization. We also perform systematic study of a variety of black hole characteristics and the spacetime around them, such as the area of the horizon, the entropy, and the radius of the photon sphere. One of the most important properties of the obtained solutions is that the scalar charge is zero and thus the scalar dipole radiation is suppressed, which leads to much weaker observational constraints compared to the majority of modified theories possessing a scalar degree of freedom. For one of the coupling functions, we could find branches of scalarized black holes which have a nontrivial structure—there is nonuniqueness of the scalarized solutions belonging to a single branch, and there is a region of the parameter space where most probably stable scalarized black holes coexist with the stable Schwarzschild black holes. Such a phenomenon can have a clear observational signature.

One of the primary aims of upcoming spaceborne gravitational wave detectors is to measure radiation in the mHz range from extreme-mass-ratio inspirals. Such a detection would place strong constraints on hypothetical departures from a Kerr description for astrophysically stable black holes. The Kerr geometry, which is unique in general relativity, admits a higher-order symmetry in the form of a Carter constant, which implies that the equations of motion describing test particle motion in a Kerr background are Liouville-integrable. In this article, we investigate whether the Carter symmetry itself is discernible from a generic deformation of the Kerr metric in the gravitational waveforms for such inspirals. We build on previous studies by constructing a new metric which respects current observational constraints, describes a black hole, and contains two non-Kerr parameters, one of which controls the presence or absence of the Carter symmetry, thereby controlling the existence of chaotic orbits, and another which serves as a generic deformation parameter. We find that these two parameters introduce fundamentally distinct features into the orbital dynamics, and evince themselves in the gravitational waveforms through a significant dephasing. Although only explored in the quadrupole approximation, this, together with a Fisher metric analysis, suggests that gravitational wave data analysis may be able to test, in addition to the governing theory of gravity, the underlying symmetries of spacetime.

The characteristic difference between a black hole and other exotic compact objects (ECOs) is the presence of the horizon. The horizon of a classical black hole acts as a one-way membrane. Due to this nature, any perturbation on the black hole must satisfy ingoing boundary conditions at the horizon. For an ECO either the horizon is replaced or modified with a surface with nonzero reflectivity. This results in a modification of the boundary condition of the perturbation around such systems. In this work, we study how tidal heating of an ECO gets modified due to the presence of a reflective surface and what implication it brings for the gravitational wave observations. We argue that the position of the reflective surface, $ϵ\gtrsim {10}^{-5}$, can have an observational impact in extreme mass ratio inspirals. We also discuss a possible degeneracy between $ϵ$ and reflectivity, $|\mathcal{R}{|}^2$, in the context of parameter estimation.

We examine the swampland conjectures in the context of generic slow-roll thawing quintessence models. Defining $\lambda \equiv |V^{\prime }({\varphi }_i)/V({\varphi }_i)|$ and $K\equiv \sqrt{1-4V^{\prime \prime }({\varphi }_i)/3V({\varphi }_i)}$, where ${\varphi }_i$ is the initial value of $\varphi$, we find regions of parameter space consistent with both observational data and with the refined de Sitter conjecture, and we show that all such models satisfy the distance conjecture. We quantify the degree of fine-tuning on $\lambda$ needed to achieve these results.

The simplest model of mirror sector dark matter maintains exact mirror symmetry, but has a baryon abundance ${\mathrm{\Omega }}_{b^{\prime }}=\beta {\mathrm{\Omega }}_b$ and a suppressed temperature $T^{\prime }=xT$ in the mirror sector; hence it depends only on two parameters, $\beta$, $x$. For sufficiently small $x$, early cosmological observables may not constrain mirror baryons from constituting all of the dark matter despite their strong self-interactions, depending on the unknown details of structure formation in the hidden sector. Here we close this loophole by simulating mirror structure formation, mapping out the allowed regions of parameter space using cosmological and astronomical data. We find that the Milky Way disk surface density and bulge mass constrain ${\mathrm{\Omega }}_{b^{\prime }}\lesssim 0.3{\mathrm{\Omega }}_b$ at the highest $T^{\prime }$ allowed by BBN and CMB ($T^{\prime }=0.5T$), or ${\mathrm{\Omega }}_{b^{\prime }}\lesssim 0.8{\mathrm{\Omega }}_b$ at lower values of $T^{\prime }$. We also briefly discuss the realization of the necessary temperature asymmetry between the SM and the mirror sector in our model with unbroken mirror symmetry.

Extragalactic foregrounds in temperature maps of the cosmic microwave background (CMB) severely limit the ability of standard estimators to reconstruct the weak lensing potential. These foregrounds are not fully removable by multifrequency cleaning or masking and can lead to large biases if not properly accounted for. For foregrounds made of a number of unclustered point sources, an estimator for the source amplitude can be derived and deprojected, removing any bias to the lensing reconstruction. We show with simulations that all of the extragalactic foregrounds in temperature can be approximated by a collection of sources with identical profiles, and that a simple bias hardening technique is effective at reducing any bias to lensing, at a minimal noise cost. We compare the performance and bias to other methods such as “shear-only” reconstruction, and discuss how to jointly deproject any arbitrary number of foregrounds, each with an arbitrary profile. In particular, for a Simons Observatory-like experiment foreground-hardened estimators allow us to extend the maximum multipole used in the reconstruction, increasing the overall statistical power by $\sim 50\%$ over the standard quadratic estimator, both in auto and cross-correlation. We conclude that source hardening outperforms the standard lensing quadratic estimator both in auto- and cross-correlation, and in terms of lensing signal-to-noise and foreground bias.

The cosmological electroweak phase transition can be strongly first order in extended particle physics models. To accurately predict the speed and shape of the bubble walls during such a transition, Boltzmann equations for the $CP$-even fluid perturbations must be solved. We point out that the equations usually adopted lead to unphysical behavior of the perturbations, for walls traveling close to or above the speed of sound in the plasma. This is an artifact that can be overcome by more carefully truncating the full Boltzmann equation. We present an improved set of fluid equations, suitable for studying the dynamics of both subsonic and supersonic walls, of interest for gravitational wave production and electroweak baryogenesis.

Systems consisting of a massive black hole and a stellar-origin compact object (CO), known as extreme-mass-ratio inspirals (EMRIs), are of great significance for space-based gravitational-wave detectors, as they will allow for testing gravitational theories in the strong field regime, and for checking the validity of the black hole no-hair theorem. In this work, we present a calculation of the EMRI rate and parameter estimation capabilities of the TianQin observatory, for various astrophysical models for these sources. We find that TianQin can observe EMRIs involving COs with a mass of $10M_{\odot }$ up to redshift $\sim 2$. We also find that detections could reach tens or hundreds per year in the most optimistic astrophysical scenarios. Intrinsic parameters are expected to be recovered to within fractional errors of $\sim {10}^{-6}$, while typical errors on the luminosity distance and sky localization are 10% and $10{\mathrm{deg}}^2$, respectively. TianQin observation of EMRIs can also constrain possible deviations from the Kerr quadrupole moment to within fractional errors $\lesssim {10}^{-4}$. We also find that a network of multiple detectors would allow for improvements in both detection rates (by a factor $\sim 1.5–3$) and in parameter estimation precision (20-fold improvement for the sky localization and fivefold improvement for the other parameters).

Ultrahigh energy cosmic rays provide the highest known energy source in the Universe to measure proton cross sections. Though conditions for collecting such data are less controlled than an accelerator environment, current generation cosmic ray observatories have large enough exposures to collect significant statistics for a reliable measurement for energies above what can be attained in the laboratory. Cosmic ray measurements of cross section use atmospheric calorimetry to measure depth of air shower maximum ($X_{\max }$), which is related to the primary particle’s energy and mass. The tail of the $X_{\max }$ distribution is assumed to be dominated by showers generated by protons, allowing measurement of the inelastic proton-air cross section. In this work, the proton-air inelastic cross section measurement, ${\sigma }_{\mathrm{p}\text{-air}}^{\mathrm{inel}}$, using data observed by Telescope Array’s Black Rock Mesa and Long Ridge fluorescence detectors and surface detector array in hybrid mode is presented. ${\sigma }_{\mathrm{p}\text{-air}}^{\mathrm{inel}}$ is observed to be $520.1\pm 35.8{[\mathrm{Stat}]}_{-42.9}^{+25.3}[\mathrm{Sys}]\mathrm{mb}$ at $\sqrt{s}=73\mathrm{TeV}$. The total proton-proton cross section is subsequently inferred from Glauber formalism and is found to be ${\sigma }_{\mathrm{pp}}^{\mathrm{tot}}={139.4}_{-21.3}^{+23.4}[\mathrm{Stat}{]}_{-25.4}^{+15.7}[\mathrm{Sys}]\mathrm{mb}$.

It is commonly stated that because terms in the beta function of a theory at the level of $\ell \ge 3$ loops and higher are scheme dependent, it is possible to define scheme transformations that can be used to remove these terms, at least in the vicinity of zero coupling. We prove that this is not, in general, possible in the situation where a beta function is not identically zero but has a vanishing one-loop term.

The Standard Model effective field theory (SMEFT) provides a consistent framework for comparing precision measurements at the LHC to the Standard Model. The observation of statistically significant nonzero SMEFT coefficients would correspond to physics beyond the Standard Model (BSM) of some sort. A more difficult question to answer is what, if any, detailed information about the nature of the underlying high scale model can be obtained from these measurements. In this work, we consider the patterns of SMEFT operators present in five example models and discuss the assumptions inherent in using global fits to make BSM conclusions. We find that including renormalization group effects has a significant impact on the interpretation of the results. As a by-product of our study, we present an updated global fit to SMEFT coefficients in the Warsaw basis including some next-to-leading order QCD corrections in the SMEFT theory.