We consider supergravity theories with 16 supercharges in Minkowski space with dimensions $d>3$. We argue that there is an upper bound on the number of massless modes in such theories depending on $d$. In particular, we show that the rank of the gauge symmetry group $G$ in $d$ dimensions is bounded by $r_G\le 26-d$. This in particular demonstrates that four-dimensional $\mathcal{N}=4$ SYM theories with rank bigger than 22, despite being consistent and indeed finite before coupling to gravity, cannot be consistently coupled to $\mathcal{N}=4$ supergravity in Minkowski space and belong to the swampland. Our argument is based on the swampland conditions of completeness of spectrum of defects as well as a strong form of the distance conjecture and relies on unitarity as well as supersymmetry of the world sheet theory of BPS strings. The results are compatible with known string constructions and provide further evidence for the string lamppost principle: that string theory lamppost seems to capture all consistent quantum gravitational theories.

We evaluate abundance anomalies generated in patches of the Universe where the baryon-to-photon ratio was locally enhanced by possibly many orders of magnitude in the range $\eta ={10}^{-10}–{10}^{-1}$. Our study is motivated by the possible survival of rare dense regions in the early Universe, the most extreme of which, above a critical threshold, collapsed to form primordial black holes. If this occurred, one may expect there to also be a significant population of early-forming stars that formed in similar but subthreshold patches. We derive a range of element abundance signatures by performing BBN simulations at high values of the baryon-to-photon ratio that may be detectable in any surviving first-generation stars of around a solar mass. Our predictions apply to metal-poor Galactic halo stars, to old globular star clusters, and to dwarf galaxies, and we compare with observations in each of these cases.

We discuss the physics of stochastic particle acceleration in relativistic magnetohydrodynamic (MHD) turbulence, combining numerical simulations of test-particle acceleration in synthetic wave turbulence spectra with detailed analytical estimates. In particular, we study particle acceleration in wavelike isotropic fast mode turbulence, in Alfvén and slow Goldreich-Sridhar type wave turbulence (properly accounting for anisotropy effects), including resonance broadening due to wave decay and pitch-angle randomization. At high particle rigidities, the contributions of those three modes to acceleration are comparable to within an order of magnitude, as a combination of several effects (partial disappearance of transit-time damping for fast modes, increased scattering rate for Alfvén, and slow modes due to resonance broadening). Additionally, we provide analytical arguments regarding acceleration beyond the regime of MHD wave turbulence, addressing the issue of nonresonant acceleration in a turbulence comprised of structures rather than waves, as well as the issue of acceleration in small-scale parallel electric fields. Finally, we compare our results to the existing literature and provide ready-to-use formulas for applications to high-energy astrophysical phenomenology.

The cosmological phenomenology of gravity is typically studied in two limits: relativistic perturbation theory (on large scales) and Newtonian gravity (required for smaller, nonlinear, scales). Traditional approaches to model-independent modified gravity are based on perturbation theory, so do not apply on nonlinear scales. Future surveys such as Euclid will produce significant data on both linear and nonlinear scales, so a new approach is required to constrain model-independent modified gravity by simultaneously using all of the data from these surveys. We use the higher order equations from the post-Friedmann approach to derive a single set of “simple 1PF” (first post-Friedmann) equations that apply in both the small scale and large scale limits, and we examine the required conditions for there to be no intermediate regime, meaning that these simple equations are valid on all scales. We demonstrate how the simple 1PF equations derived here can be used as a model-independent framework for modified gravity that applies on all cosmological scales, and we present an algorithm for determining which modified gravity theories are subsumed under this approach. This modified gravity framework provides a rigorous approach to phenomenological N-body simulations, and paves the way to consistently using all of the data from upcoming surveys to constrain modified gravity in a model-independent fashion.

The memory effect at null infinity, ${\mathcal{I}}^{+}$, can be defined in terms of the permanent relative displacement of test particles (at leading order in $1/r$) resulting from the passage of a burst of gravitational radiation. In $D=4$ spacetime dimensions, the memory effect can be characterized by the supertranslation relating the “good cuts” of ${\mathcal{I}}^{+}$ in the stationary eras at early and late retarded times. It also can be characterized in terms of charges and fluxes associated with supertranslations. Black hole event horizons are in many ways analogous to ${\mathcal{I}}^{+}$. We consider here analogous definitions of memory for a black hole, assuming that the black hole is approximately stationary at early and late advanced times, so that its event horizon is described by a Killing horizon (assumed nonextremal) at early and late times. We give prescriptions for defining preferred foliations of nonextremal Killing horizons. We give a definition of the memory tensor for a black hole in terms of the “permanent relative displacement” of the null geodesic generators of the event horizon between the early and late time stationary eras. We show that preferred foliations of the event horizon in the early and late time eras are related by a Chandrasekaran-Flanagan-Prabhu (CFP) supertranslation. However, we find that the memory tensor for a black hole horizon does not appear to be related to the CFP symmetries or their charges and fluxes in a manner similar to that occurring at ${\mathcal{I}}^{+}$.

New physics in the neutrino sector might be necessary to address anomalies between different neutrino oscillation experiments. Intriguingly, it also offers a possible solution to the discrepant cosmological measurements of $H_0$ and ${\sigma }_8$. We show here that delaying the onset of neutrino free streaming until close to the epoch of matter-radiation equality can naturally accommodate a larger value for the Hubble constant $H_0=72.3\pm 1.4\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$ and a lower value of the matter fluctuations ${\sigma }_8=0.786\pm 0.020$, while not degrading the fit to the cosmic microwave background (CMB) damping tail. We achieve this by introducing neutrino self-interactions in the presence of a nonvanishing sum of neutrino masses. Without explicitly incorporating additional neutrino species, this strongly interacting neutrino cosmology prefers $N_{\mathrm{eff}}=4.02\pm 0.29$, which has interesting implications for particle model building and neutrino oscillation anomalies. We show that the absence of the neutrino free-streaming phase shift on the CMB can be compensated for by shifting the values of several cosmological parameters, hence providing an important caveat to the detections made in the literature. Due to their impact on the evolution of the gravitational potential at early times, self-interacting neutrinos and their subsequent decoupling leave a rich structure on the matter power spectrum. In particular, we point out the existence of a novel localized feature appearing on scales entering the horizon at the onset of neutrino free streaming. While the interacting neutrino cosmology provides a better global fit to current cosmological data, we find that traditional Bayesian analyses penalize the model as compared to the standard cosmological scenario due to the relatively narrow range of neutrino interaction strengths that is favored by the data. The model we present illustrates desirable cosmological impacts to simultaneously resolve the Hubble constant and matter clustering tensions rather than proposing a viable particle model. Our analysis shows that it is possible to find radically different cosmological models that nonetheless provide excellent fits to the data, hence providing an impetus to thoroughly explore alternate cosmological scenarios.

We study the potential of future electron-ion collider (EIC) data to probe four-fermion operators in the Standard Model effective field theory (SMEFT). The ability to perform measurements with both polarized electron and proton beams at the EIC provides a powerful tool that can disentangle the effects from different SMEFT operators. We compare the potential constraints from an EIC with those obtained from Drell-Yan data at the Large Hadron Collider. We show that EIC data play an important complementary role since they probe combinations of Wilson coefficients not accessible through available Drell-Yan measurements.

We present a fast implementation of the next-to-leading order (one-loop) redshift-space galaxy power spectrum by using FFTLog-based methods. Desjacques et al. [J. Cosmol. Astropart. Phys. 12 (2018) 035] have shown that the one-loop galaxy power spectrum in redshift space can be computed with 28 independent loop integrals with 22 bias parameters. Analytical calculation of the angular part of the loop integrals leaves the radial part in the form of a spherical Bessel transformation that is ready to be integrated numerically by using the FFTLog transformation. We find that the original 28 loop integrals can be solved with a total of 85 unique FFTLog transformations, yet leading to a few orders of magnitude speed up over traditional multidimensional integration.

Fast radio bursts (FRBs) probe the electron density of the universe along the path of propagation, making high redshift FRB sensitive to the helium reionization epoch. We analyze the signal to noise with which a detection of the amplitude of reionization can be made, and its redshift, for various cases of future FRB survey samples, assessing survey characteristics including total number, redshift distribution, peak redshift, redshift depth, and number above the reionization redshift, as well as dependence on reionization redshift. We take into account scatter in the dispersion measure due to an inhomogeneous intergalactic medium (IGM) and uncertainty in the FRB host and environment dispersion measure, as well as cosmology. For a future survey with 7000 FRBs extending out to $z=5$, and a sudden reionization, the detection of helium reionization can approach the $5\sigma$ level and the reionization redshift be determined to $\sigma (z_r)\approx 0.24$ in an optimistic scenario, or $2\sigma$ and $\sigma (z_r)\approx 0.34$ taking into account further uncertainties on IGM fraction evolution and redshift uncertainties.

We present results from a numerical study of rotating black hole formation in 3-dimensional asymptotically anti–de Sitter (AdS) spacetime, focusing on the structure of the black hole interior. While black holes in ${\mathrm{AdS}}_3$ are of theoretical interest for a wide variety of reasons, we choose to study this system primarily as a toy model for astrophysical (4-dimensional) black holes formed from gravitational collapse. We investigate the effect of angular momentum on the geometry inside the event horizon, and see qualitative changes in the interior structure as a function of the spin parameter. For low spins, we find that a central spacelike curvature singularity forms, connecting to a singular, null Cauchy horizon. For spins above a threshold consistent with the linear analysis of Dias, Reall and Santos, curvature on the Cauchy horizon remains bounded, signaling a violation of the strong cosmic censorship conjecture. Further increasing the spin leads to a decrease in the relative size of the spacelike branch of the singularity, which vanishes completely above a second threshold. In these high-spin cases, the interior evolution is bounded by a regular Cauchy horizon, which extends all the way inward to a regular, timelike origin. We further explore the geodesic focusing (“gravitational shock-wave”) effect predicted to occur along the outgoing branch of the inner horizon, first described by Marolf and Ori. Remarkably, we observe the effect at late times in all of the black holes we form, even those in which the inner apparent horizon collapses to zero radius early in their evolution.

We investigate the prospect of an alternative laboratory-based search for the coupling of axions and axionlike particles to photons. Here, the collision of two laser beams resonantly produces axions, and a signal photon is detected after magnetic reconversion, as in light-shining-through-walls (LSW) experiments. Conventional searches, such as LSW or anomalous birefringence measurements, are most sensitive to axion masses for which substantial coherence can be achieved; this is usually well below optical energies. We find that using currently available high-power laser facilities, the bounds that can be achieved by our approach outperform traditional LSW at axion masses between 0.5–6 eV, set by the optical laser frequencies and collision angle. These bounds can be further improved through coherent scattering off laser substructures, probing axion-photon couplings down to $g_{a\gamma \gamma }\sim {10}^{-8}{\mathrm{GeV}}^{-1}$, comparable with existing CAST bounds. Assuming a day long measurement per angular step, the QCD axion band can be reached.

We propose a generalization of $S$-folds to 4d $\mathcal{N}=2$ theories. This construction is motivated by the classification of rank one 4d $\mathcal{N}=2$ super-conformal field theories (SCFTs), which we reproduce from D3-branes probing a configuration of $\mathcal{N}=2$ $S$-folds combined with 7-branes. The main advantage of this point of view is that realizes both Coulomb and Higgs branch flows and allows for a straightforward generalization to higher rank theories.

There are currently several existing and proposed experiments designed to probe sub-GeV dark matter (DM) using electron ionization in various materials. The projected signal rates for these experiments assume that this ionization yield arises only from DM scattering directly off electron targets, ignoring secondary ionization contributions from DM scattering off nuclear targets. We investigate the validity of this assumption and show that if sub-GeV DM couples with comparable strength to both protons and electrons, as would be the case for a dark photon mediator, the ionization signal from atomic scattering via the Migdal effect scales with the atomic number $Z$ and 3-momentum transfer $\mathbf{q}$ as $Z^2{\mathbf{q}}^2$. The result is that the Migdal effect is always subdominant to electron scattering when the mediator is light, but that Migdal-induced ionization can dominate over electron scattering for heavy mediators and DM masses in the hundreds of MeV range. We put these two ionization processes on identical theoretical footing, address some theoretical uncertainties in the choice of atomic wave functions used to compute rates, and discuss the implications for DM scenarios where the Migdal process dominates, including for XENON10, XENON100, and the recent XENON1T results on light DM scattering.

The element $|V_{cb}|$ of the Cabibbo-Kobayashi-Maskawa matrix is measured using semileptonic $B_s^0$ decays produced in proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3{\mathrm{fb}}^{-1}$. Rates of $B_s^0\to D_s^{-}{\mu }^{+}{\nu }_{\mu }$ and $B_s^0\to D_s^{*-}{\mu }^{+}{\nu }_{\mu }$ decays are analyzed using hadronic form-factor parametrizations derived either by Caprini, Lellouch and Neubert (CLN) or by Boyd, Grinstein and Lebed (BGL). The measured values of $|V_{cb}|$ are $(41.4\pm 0.6\pm 0.9\pm 1.2)\times {10}^{-3}$ and $(42.3\pm 0.8\pm 0.9\pm 1.2)\times {10}^{-3}$ in the CLN and BGL parametrization, respectively. The first uncertainty is statistical, the second systematic, and the third is due to the external inputs used in the measurement. These results are in agreement with those obtained from decays of $B^{+}$ and $B^0$ mesons. They are the first determinations of $|V_{cb}|$ at a hadron-collider experiment and the first using $B_s^0$ meson decays.

We reconsider our former determination of the chiral quark condensate $⟨\overline{q}q⟩$ from the related QCD spectral density of the Euclidean Dirac operator, using our renormalization group optimized perturbation (RGOPT) approach. Thanks to the recently available complete five-loop QCD RG coefficients, and some other related four-loop results, we can extend our calculations exactly to $N^{4}LO$ (five loops) RGOPT, and partially to $N^{5}LO$ (six loops), the latter within a well-defined approximation accounting for all six-loop contents exactly predictable from five-loop RG properties. The RGOPT results overall show a very good stability and convergence, giving primarily the RG-invariant (RGI) condensate, $⟨\overline{q}q{⟩}_{\mathrm{RGI}}^{1/3}(n_f=0)=-(0.840_{-0.016}^{+0.020}){\overline{\mathrm{\Lambda }}}_0$, $⟨\overline{q}q{⟩}_{\mathrm{RGI}}^{1/3}(n_f=2)=-(0.781_{-0.009}^{+0.019}){\overline{\mathrm{\Lambda }}}_2$, $⟨\overline{q}q{⟩}_{\mathrm{RGI}}^{1/3}(n_f=3)=-(0.751_{-0.010}^{+0.019}){\overline{\mathrm{\Lambda }}}_3$, where ${\overline{\mathrm{\Lambda }}}_{n_f}$ is the basic QCD scale in the $\overline{\mathrm{MS}}$ scheme for $n_f$ quark flavors, and the range spanned is our rather conservative estimated theoretical error. This leads e.g., to $⟨\overline{q}q{⟩}_{n_f=3}^{1/3}(2\mathrm{GeV})=-(273_{-4}^{+7}\pm 13)\mathrm{MeV}$, using the latest ${\overline{\mathrm{\Lambda }}}_3$ values giving the second uncertainties. We compare our results with some other recent determinations. As a by-product of our analysis we also provide complete five-loop and partial six-loop expressions of the perturbative QCD spectral density, that may be useful for other purposes.

Black hole images present an annular region of enhanced brightness. In the absence of propagation effects, this “photon ring” has universal features that are completely governed by general relativity and independent of the details of the emission. Here, we show that the polarimetric image of a black hole also displays universal properties. In particular, the photon ring exhibits a self-similar pattern of polarization that encodes the black hole spin. We explore the corresponding universal polarimetric signatures of the photon ring on long interferometric baselines, and propose a method for measuring the black hole spin using a sparse interferometric array. These signatures could enable spin measurements of the supermassive black hole in M87, as well as precision tests of general relativity in the strong field regime, via a future extension of the Event Horizon Telescope to space.

The framework of perturbative algebraic quantum field theory (pAQFT) is used to construct QFT models on causal sets. We discuss various discretised wave operators, including a new proposal based on the idea of a “preferred past,” which we also introduce, and show how they may be used to construct classical free and interacting field theory models on a fixed causal set; additionally, we describe how the sensitivity of observables to changes in the background causal set may be encapsulated in a relative Cauchy evolution. These structures are used as the basis of a deformation quantization, using the methods of pAQFT. The SJ state is defined and discussed as a particular quantum state on the free quantum theory. Finally, using the framework of pAQFT, we construct interacting models for arbitrary interactions that are smooth functions of the field configurations. This is the first construction of such a wide class of models achieved in QFT on causal sets.

Direct-detection experiments for light dark matter are making enormous leaps in reaching previously unexplored model space. Several recent proposals rely on collective excitations, where the experimental sensitivity is highly dependent on detailed properties of the target material, well beyond just nucleus mass numbers as in conventional searches. It is thus important to optimize the target choice when considering which experiment to build. We carry out a comparative study of target materials across several detection channels, focusing on electron transitions and single (acoustic or optical) phonon excitations in crystals, as well as the traditional nuclear recoils. We compare materials currently in use in nuclear recoil experiments (Si, Ge, NaI, CsI, ${\mathrm{CaWO}}_4$), a few of which have been proposed for light dark matter experiments (GaAs, ${\mathrm{Al}}_2{\mathrm{O}}_3$, diamond), as well as 16 other promising polar crystals across all detection channels. We find that target- and dark-matter-model-dependent reach is largely determined by a small number of material parameters: speed of sound, electronic band gap, mass number, Born effective charge, high-frequency dielectric constant, and optical phonon energies. We showcase, for each of the two benchmark models, an exemplary material that has a better reach than in any currently proposed experiment.

Inelastic dark matter and strongly interacting dark matter are poorly constrained by direct detection experiments since they both require the scattering event to deliver energy from the nucleus into the dark matter in order to have observable effects. We propose to test these scenarios by searching for the collisional deexcitation of metastable nuclear isomers by the dark matter particles. The longevity of these isomers is related to a strong suppression of $\gamma$- and $\beta$-transitions, typically inhibited by a large difference in the angular momentum for the nuclear transition. The collisional deexcitation by dark matter is possible since heavy dark matter particles can have a momentum exchange with the nucleus comparable to the inverse nuclear size, hence lifting tremendous angular momentum suppression of the nuclear transition. This deexcitation can be observed either by searching for the direct effects of the decaying isomer, or through the rescattering or decay of excited dark matter states in a nearby conventional dark matter detector setup. Existing nuclear isomer sources such as naturally occurring ${}^{180m}\mathrm{Ta}$, ${}^{137m}\mathrm{Ba}$ produced in decaying Cesium in nuclear waste, ${}^{177m}\mathrm{Lu}$ from medical waste, and ${}^{178m}\mathrm{Hf}$ from the Department of Energy storage can be combined with current dark matter detector technology to search for this class of dark matter.

We present 12 new simulations of unequal mass neutron star mergers. The simulations are performed with the spec code, and utilize nuclear-theory-based equations of state and a two-moment gray neutrino transport scheme with an improved energy estimate based on evolving the number density. We model the neutron stars with the SFHo, LS220, and DD2 equations of state (EOS) and we study the neutrino and matter emission of all 12 models to search for robust trends between binary parameters and emission characteristics. We find that the total mass of the dynamical ejecta exceeds $0.01M_{\odot }$ only for SFHo with weak dependence on the mass ratio across all models. We find that the ejecta have a broad electron fraction ($Y_e$) distribution ($\approx 0.06–0.48$), with mean 0.2. $Y_e$ increases with neutrino irradiation over time, but decreases with increasing binary asymmetry. We also find that the models have ejecta with a broad asymptotic velocity distribution ($\approx 0.05–0.7c$). The average velocity lies in the range $0.2c-0.3c$ and decreases with binary asymmetry. Furthermore, we find that disk mass increases with binary asymmetry and stiffness of the EOS. The $Y_e$ of the disk increases with softness of the EOS. The strongest neutrino emission occurs for the models with soft EOS. For (anti) electron neutrinos we find no significant dependence of the magnitude or angular distribution or neutrino luminosity with mass ratio. The heavier neutrino species have a luminosity dependence on mass ratio but an angular distribution which does not change with mass ratio.