We consider scattering of massless higher-spin particles in the eikonal regime in four dimensions. By demanding the absence of asymptotic superluminality, corresponding to positivity of the eikonal phase, we place constraints on the possible cubic couplings which can appear in the theory. The cubic couplings come in two types: lower-derivative non-Abelian vertices and higher-derivative Abelian vertices made out of gauge-invariant curvature tensors. We find that the Abelian couplings between massless higher spins lead to an asymptotic time advance for certain choices of polarizations, indicating that these couplings should be absent unless new states come in at the scale suppressing the derivatives in these couplings. A subset of non-Abelian cubic couplings are consistent with eikonal positivity, but are ruled out by consistency of the four-particle amplitude away from the eikonal limit. The eikonal constraints are, therefore, complementary to the four-particle test, ruling out even trivial cubic curvature couplings in any theory with a finite number of massless higher spins and no new physics at the scale suppressing derivatives in these vertices.

Cosmological measurements over the next decade will enable us to shed light on the content and evolution of the Universe. Complementary measurements of the cosmic microwave background (CMB) and baryon acoustic oscillations are expected to allow an indirect determination of the sum of neutrino masses, within the framework of the flat $\mathrm{\Lambda }\mathrm{CDM}$ model. However, possible deviations from $\mathrm{\Lambda }\mathrm{CDM}$ such as a nonzero cosmological curvature or a dark energy equation of state with $w\ne -1$ would leave similar imprints on the expansion rate of the Universe and clustering of matter. We show how future CMB measurements can be combined with late-time measurements of galaxy clustering and cosmic shear from the Large Synoptic Survey Telescope to alleviate this degeneracy. Together, they are projected to reduce the uncertainty on the neutrino mass sum to 30 meV within this more general cosmological model. Achieving a $3\sigma$ measurement of the minimal 60 meV mass sum (or $4\sigma$ assuming $w=-1$) will require a fivefold improved measurement of the optical depth to reionization, obtainable through a large-scale CMB polarization measurement.

We propose a universal mechanism of producing dark matter and baryon (lepton) charge at the stage of the quasi-de Sitter expansion of the Universe—inflation. The key ingredient of the mechanism is a linear coupling of the field, responsible for a generation of dark matter or baryon (lepton) charge, to a function of the inflaton. During inflation this induces almost constant force dragging the corresponding field to the nonzero value. This force explicitly breaks quantum numbers associated with dark matter/baryon abundance at later stages. As a particular realization of the mechanism we introduce a superheavy complex scalar field with the mass larger than the Hubble rate during the last e-folds of inflation. The global $U(1)$ symmetry is violated due to the linear coupling of the phase of the complex scalar to the inflaton. The symmetry breaking leads to the generation of a nonzero Noether charge. The latter is directly related to the dark matter abundance, or, alternatively, can be converted into baryon asymmetry, if the complex scalar carries the baryon charge.

Parametrized representations of the equation of state play an important role in efforts to measure the properties of the matter in the cores of neutron stars using astronomical observations. New representations are presented here that are capable of representing any equation of state to any desired level of accuracy, while automatically imposing causality and thermodynamic stability constraints. Numerical tests are presented that measure how accurately and efficiently these new parameterizations represent a collection of causal nuclear-theory model equations of state.

A component of the dark matter could consist of two darkly charged particles with a large mass ratio and a massless force carrier. This “atomic” dark sector could behave much like the baryonic sector, cooling and fragmenting down to stellar-mass or smaller scales. Past studies have shown that cosmic microwave background and large-scale structure constraints rule out $\gtrsim 5\%$ of the dark matter to behave in this manner. However, we show that, even with percent level mass fractions, a dark atomic sector could affect some extragalactic and galactic observables. We track the cooling and merger history of an atomic dark component for much of the interesting parameter space. Unlike the baryons, where stellar feedback (driven by nuclear physics) delays the formation and growth of galaxies, cooling dark atomic gas typically results in disks forming earlier, leaving more time for their destruction via mergers. Rather than disks in Milky Way sized halos, we find the end product is typically spheroidal structures on galactic scales or dark atom fragments distributed on halo scales. This result contrasts with previous studies, which had assumed that the dark atoms would result in dark disks. Furthermore the dark atoms condense into dense clumps, analogous to how the baryons fragment on solar-mass scales. We estimate the size of these dark clumps, and use these estimates to show that viable atomic dark matter parameter space is ruled out by stellar microlensing, by the half-light radii of ultrafaint dwarf galaxies, and by Milky Way mass-to-light inferences.

In this paper, we present a model for sub-MeV dark matter with strong self-interactions which can solve some of the small-scale crisis of the $\mathrm{\Lambda }\mathrm{CDM}$. The dark matter is a Majorana fermion with only off-diagonal interactions with a hidden $U(1{)}_D$ gauge boson. The relic density is obtained by freeze-out of Boltzmann suppressed annihilations to a light fermionic species. The self-interaction is a one-loop process and constrained to be between 0.1 to $1{\mathrm{cm}}^2/\mathrm{g}$. Severe constraints from the BBN on $N_{\mathrm{eff}}$ require that the dark and visible sector are not in thermal equilibrium during freeze-out. The effect of this temperature asymmetry is studied.

We consider the cosmological dynamics of a scalar field in a potential with multiple troughs and peaks. We show that the dynamics of the scalar field will evolve from light dark matter–like behavior (such as that of a light axion) to a combination of heavy dark matter–like and dark energy–like behavior. We discuss the phenomenology of such a model, explaining how it can give rise to the cosmological constant as well as how it can decouple the dark sector densities between the time of recombination and today, for both the homogeneous background and perturbations. The final form of the dark matter is axionlike, but with abundance and primordial isocurvature modes taking very different values from traditional, axionic, dark matter.

Above a critical dark matter-nucleus scattering cross section any terrestrial direct detection experiment loses sensitivity to dark matter, since the Earth crust, atmosphere, and potential shielding layers start to block off the dark matter particles. This critical cross section is commonly determined by describing the average energy loss of the dark matter particles analytically. However, this treatment overestimates the stopping power of the Earth crust. Therefore the obtained bounds should be considered as conservative. We perform Monte Carlo simulations to determine the precise value of the critical cross section for various direct detection experiments and compare them to other dark matter constraints in the low mass regime. In this region we find parameter space where typical underground and surface detectors are completely blind to dark matter. This “hole” in the parameter space can hardly be closed with an increase in the detector exposure. Dedicated surface or high-altitude experiments may be the only way to directly probe this part of the parameter space.

Partial compositeness is a key ingredient of models where the electroweak symmetry is broken by a composite Higgs state. Recently, a UV completion of partial compositeness was proposed, featuring a new, strongly coupled gauge interaction as well as new fundamental fermions and scalars. We work out the full flavor structure of the minimal realization of this idea and investigate in detail the consequences for flavor physics. While $CP$ violation in kaon mixing represents a significant constraint on the model, we find many viable parameter points passing all precision tests. We also demonstrate that the recently observed hints for a violation of lepton flavor universality in $B\to K^{(*)}\ell \ell$ decays can be accommodated by the model, while the anomalies in $B\to D^{(*)}\tau \nu$ cannot be explained while satisfying constraints on $Z$ couplings from measurements at the Large Electron-Positron Collider.

We consider the $A_4$, $S_4$, and $A_5$ discrete lepton flavor symmetries in the case of 3-neutrino mixing, broken down to nontrivial residual symmetries in the charged lepton and neutrino sectors in such a way that at least one of them is a $Z_2$. Such symmetry breaking patterns lead to predictions for some of the three neutrino mixing angles and/or the leptonic Dirac $CP$ violation phase $\delta$ of the neutrino mixing matrix. We assess the viability of these predictions by performing a statistical analysis which uses as an input the latest global data on the neutrino mixing parameters. We find 14 phenomenologically viable cases providing distinct predictions for some of the mixing angles and/or the Dirac phase $\delta$. Employing the current best fit values of the three neutrino mixing angles, we perform a statistical analysis of these cases taking into account the prospective uncertainties in the determination of the mixing angles, planned to be achieved in currently running (Daya Bay) and the next generation (JUNO, T2HK, DUNE) of neutrino oscillation experiments. We find that only six cases would be compatible with these prospective data. We show that this number is likely to be further reduced by a precision measurement of $\delta$.

The nature of the thermal phase transition of two flavor QCD in the chiral limit has an important implication for the QCD phase diagram. We carry out lattice QCD simulations in an attempt to address this problem. Simulations are conducted with a Symanzik-improved gauge action and the Highly Improved Staggered Quark fermion action. Within the imaginary chemical potential formulation, five different quark masses, $am=0.020$, 0.018, 0.015, 0.013, 0.010, and four different lattice volumes, $N_s=8$, 12, 16, 20, with temporal extent $N_t=4$ are used to explore the scaling behavior. At each of the quark masses, the Binder cumulants of the chiral condensate on different lattice volumes approximately intersect at one point. We find that at the intersection point the Binder cumulant $B_4(am,a{\mu }_c)$ is around 3, which deviates from the $Z(2)$ universality class value 1.604. However, based on the expectations of $Z(2)$ criticality, the fitting result only with the data from the largest lattice volume $N_s=20$ agrees well with earlier result [Phys. Rev. D 90, 074030 (2014). This fact implies that, although the finite cutoff effects could be reduced with Highly Improved Staggered Quark fermions even on $N_t=4$ lattices, larger lattices with spatial extent $N_s>=20$ for such studies are needed to control finite volume effects.

A cluster expansion model (CEM), representing a relativistic extension of Mayer’s cluster expansion, is constructed to study baryon number fluctuations in QCD. The temperature dependent first two coefficients, corresponding to the partial pressures in the baryon number $B=1$ and $B=2$ sectors, are the only model input, which we fix by recent lattice data at imaginary baryochemical potential. All other coefficients are constructed in terms of the first two and required to match the Stefan-Boltzmann limit of noninteracting quarks and gluons at $T\to \infty$. The CEM allows calculations of the baryon number susceptibilities ${\chi }_k^B$ to arbitrary order. We obtain excellent agreement with all available lattice data for the baryon number fluctuation measures ${\chi }_2^B$, ${\chi }_4^B$, ${\chi }_6^B$ and predict higher order susceptibilities, that are not yet available from Lattice QCD. The calculated susceptibilities are then used to extract the radius of convergence of the Taylor expansion of the pressure. The commonly used ratio test fails due to the nontrivial asymptotic behavior of the Taylor coefficients. At the same time, a more elaborate estimator provides finite convergence radii at all considered temperatures and in agreement with the singularities of Padé approximants. The associated singularities lie in the complex ${\mu }_B/T$-plane and appear smoothly connected to the Roberge-Weiss transition at high temperatures and imaginary chemical potential. No evidence for a phase transition at ${\mu }_B/T\lesssim \pi$ and $T>135\mathrm{MeV}$ is found.

The black hole area theorem implies that when two black holes merge, the area of the final black hole should be greater than the sum of the areas of the two original black holes. We examine how this prediction can be tested with gravitational-wave observations of binary black holes. By separately fitting the early inspiral and final ringdown stages, we calculate the posterior distributions for the masses and spins of the two initial and the final black holes. This yields posterior distributions for the change in the area and thus a statistical test of the validity of the area increase law. We illustrate this method with a GW150914-like binary black hole waveform calculated using numerical relativity, and detector sensitivities representative of both the first observing run and the design configuration of Advanced LIGO. We obtain a $\sim 74.6\%$ probability that the simulated signal is consistent with the area theorem with current sensitivity, improving to $\sim 99.9\%$ when Advanced LIGO reaches design sensitivity. An important ingredient in our test is a method of estimating when the postmerger signal is well fit by a damped sinusoid ringdown waveform.

A novel idea is proposed for a natural solution of the dark energy and its cosmic coincidence problem. The existence of local antigravity sources, associated with astrophysical matter configurations distributed throughout the Universe, can lead to a recent cosmic acceleration effect. Various physical theories can be compatible with this idea, but here, in order to test our proposal, we focus on quantum originated spherically symmetric metrics matched with the cosmological evolution through the simplest Swiss cheese model. In the context of asymptotically safe gravity, we have explained the observed amount of dark energy using Newton’s constant, the galaxy or cluster length scales, and dimensionless order-one parameters predicted by the theory, without fine-tuning or extra unproven energy scales. The interior modified Schwarzschild–de Sitter metric allows us to approximately interpret this result as that the standard cosmological constant is a composite quantity made of the above parameters, instead of a fundamental one.

We examine “dynamical similarities” in the Lagrangian framework. These are symmetries of an intrinsically determined physical system under which observables remain unaffected, but the extraneous information is changed. We establish three central results in this context: (i) Given a system with such a symmetry there exists a system of invariants which form a subalgebra of phase space, whose evolution is autonomous; (ii) this subalgebra of autonomous observables evolves as a contact system, in which the frictionlike term describes evolution along the direction of similarity; (iii) the contact Hamiltonian and one-form are invariants, and reproduce the dynamics of the invariants. As the subalgebra of invariants is smaller than phase space, dynamics is determined only in terms of this smaller space. We show how to obtain the contact system from the symplectic system, and the embedding which inverts the process. These results are then illustrated in the case of homogeneous Lagrangians, including flat cosmologies minimally coupled to matter; the n-body problem and homogeneous, anisotropic cosmology.

The lensing convergence measurable with future CMB surveys like CMB-S4 will be highly correlated with the clustering observed by deep photometric large scale structure (LSS) surveys such as the LSST, with cross-correlation coefficient as high as 95%. This will enable use of sample variance cancellation techniques to determine cosmological parameters, and use of cross-correlation measurements to break parameter degeneracies. Assuming large sky overlap between CMB-S4 and LSST, we show that a joint analysis of CMB-S4 lensing and LSST clustering can yield very tight constraints on the matter amplitude ${\sigma }_8(z)$, halo bias, and $f_{\mathrm{NL}}$, competitive with the best stage IV experiment predictions, but using complementary methods, which may carry different and possibly lower systematics. Having no sky overlap between experiments degrades the precision of ${\sigma }_8(z)$ by a factor of 20, and that of $f_{\mathrm{NL}}$ by a factor of 1.5 to 2. Without CMB lensing, the precision always degrades by an order of magnitude or more, showing that a joint analysis is critical. Our results also suggest that CMB lensing in combination with LSS photometric surveys is a competitive probe of the evolution of structure in the redshift range $z\simeq 1–7$, probing a regime that is not well tested observationally. We explore predictions against other surveys and experiment configurations, finding that wide patches with maximal sky overlap between CMB and LSS surveys are most powerful for ${\sigma }_8(z)$ and $f_{\mathrm{NL}}$.

All-sky surveys for isolated continuous gravitational waves present a significant data-analysis challenge. Semicoherent search methods are commonly used to efficiently perform the computationally-intensive task of searching for these weak signals in the noisy data of gravitational-wave detectors such as LIGO and Virgo. We present a new implementation of a semicoherent search method, weave, that for the first time makes full use of a parameter-space metric to generate banks of search templates at the correct resolution, combined with optimal lattices to minimize the required number of templates and hence the computational cost of the search. We describe the implementation of weave and associated design choices and characterize its behavior using semianalytic models.

The extragalactic $\gamma$-ray background (EGB) arises from the accumulation of $\gamma$-ray emissions from resolved and unresolved extragalactic sources as well as diffuse processes. It is important to study the statistical properties of the EGB in the context of cosmological structure formation. Known astrophysical $\gamma$-ray sources such as blazars, star-forming galaxies, and radio galaxies are expected to trace the underlying cosmic matter density distribution. We explore the correlation of the EGB from Fermi-LAT data with the large-scale matter density distribution from the Subaru Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) survey. We reconstruct an unbiased surface matter density distribution $\kappa$ at $z\lesssim 1$ by applying weak gravitational lensing analysis to the first-year HSC data. We then calculate the $\gamma -\kappa$ cross-correlation. Our measurements are consistent with a null detection, but a weak correlation is found at angular scales of 30–60 arcmin, especially when distant source galaxies at $z>1$ are used for the lensing $\kappa$ reconstruction. The large-scale correlation suggests strong clustering of high-redshift $\gamma$-ray sources such as blazars. However, the inferred bias factor of 4–5 is larger by about a factor of 2 than results from other clustering analyses. The final HSC data covering 1400 squared degrees will play an essential role to determine accurately the blazar bias at $z>0.5$.

For third generation gravitational wave detectors, such as the Einstein Telescope, gravitational wave signals from binary neutron stars can last up to a few days before the neutron stars merge. To estimate the measurement uncertainties of key signal parameters, we develop a Fisher matrix approach which accounts for effects on such long duration signals of the time-dependent detector response and the Earth’s rotation. We use this approach to characterize the sky localization uncertainty for gravitational waves from binary neutron stars at 40, 200, 400, 800, and 1600 Mpc, for the Einstein Telescope and Cosmic Explorer individually and operating as a network. We find that the Einstein Telescope alone can localize the majority of detectable binary neutron stars at a distance of $\le 200\mathrm{Mpc}$ to within $100{\mathrm{deg}}^2$ with 90% confidence. A network consisting of the Einstein Telescope and Cosmic Explorer can enhance the sky localization performance significantly—with the 90% credible region of $\mathcal{O}(1){\mathrm{deg}}^2$ for most sources at $\le 200\mathrm{Mpc}$ and $\le 100{\mathrm{deg}}^2$ for most sources at $\le 1600\mathrm{Mpc}$. We also investigate the prospects for third generation detectors identifying the presence of a signal prior to merger. To do this, we require a signal to have a network signal-to-noise ratio of $\ge 12$ and $\ge 5.5$ for at least two interferometers, and to have a 90% credible region for the sky localization that is no larger than $100{\mathrm{deg}}^2$. We find that the Einstein Telescope can send out such “early-warning” detection alerts 1–20 hours before merger for 100% of detectable binary neutron stars at 40 Mpc and for $\sim 58\%$ of sources at 200 Mpc. For sources at a distance of 400 Mpc, a network of the Einstein telescope and Cosmic Explorer can produce detection alerts up to $\sim 3$ hours prior to merger for 98% of detectable binary neutron stars.

We present a phenomenological study of Dirac electroweakinos in a $U(1{)}_R$ extension of the minimal supersymmetric standard model with a strictly $R$-symmetric Higgs sector (minimal $R$-symmetric supersymmetric standard model) and gauge-mediated supersymmetry breaking. One of the distinguishing features of the MRSSM is that the lightest chargino can be lighter than the lightest neutralino. Decays from the next-to-lightest-supersymmetric particle (NLSP) chargino to the gravitino lightest supersymmetric particle will produce exotic signals. We apply LHC-13 mass limits from both prompt and long-lived searches to the chargino NLSP regime of the MRSSM. Imposing the additional constraints coming from the 125 GeV Higgs and from the electroweak sector, regions of the parameter space are found where the gravitino lightest supersymmetric particle, chargino NLSP scenario survives all current bounds. We also show that the fine-tuning of the model can reach a level slightly better than sub-percent with our choice of parameters.