We analyze the global behavior of the growth index of cosmic inhomogeneities in an isotropic homogeneous universe filled by cold nonrelativistic matter and dark energy (DE) with an arbitrary equation of state. Using a dynamical system approach, we find the critical points of the system. That unique trajectory for which the growth index $\gamma$ is finite from the asymptotic past to the asymptotic future is identified as the so-called heteroclinic orbit connecting the critical points $({\mathrm{\Omega }}_m=0,{\gamma }_{\infty })$ in the future and $({\mathrm{\Omega }}_m=1,{\gamma }_{-\infty })$ in the past. The first is an attractor while the second is a saddle point, confirming our earlier results. Further, in the case when a fraction of matter (or DE tracking matter) $ϵ{\mathrm{\Omega }}_m^{\mathrm{tot}}$ remains unclustered, we find that the limit of the growth index in the past ${\gamma }_{-\infty }^{ϵ}$ does not depend on the equation of state of DE, in sharp contrast with the case $ϵ=0$ (for which ${\gamma }_{-\infty }$ is obtained). We show indeed that there is a mathematical discontinuity: one cannot obtain ${\gamma }_{-\infty }$ by taking ${\lim }_{ϵ\to 0}{\gamma }_{-\infty }^{ϵ}$ (i.e., the limits $ϵ\to 0$ and ${\mathrm{\Omega }}_m^{\mathrm{tot}}\to 1$ do not commute). We recover in our analysis that the value ${\gamma }_{-\infty }^{ϵ}$ corresponds to tracking DE in the asymptotic past with constant $\gamma ={\gamma }_{-\infty }^{ϵ}$ found earlier.

Gravitational waves from compact binary coalescence sources can be decomposed into spherical-harmonic multipoles, the dominant being the quadrupole ($(l,|m|)=(2,2)$) modes. The contribution of subdominant modes toward total signal power increases with increasing binary mass ratio and source inclination to the detector. It is well known that in these cases neglecting higher modes could lead to measurement biases, but these have not yet been quantified with a higher-mode model that includes spin effects. In this study, we use the multimode aligned-spin phenomenological waveform model imrphenomhm [1] to investigate the effects of including multimode content in estimating source parameters and contrast the results with using a quadrupole-only model (imrphenomd). We use as sources imrphenomhm and hybrid effective-one-body–numerical-relativity waveforms with zero spin over a range of mass-ratio and inclination combinations, and recover the parameters with imrphenomhm and imrphenomd. These allow us to quantify the accuracy of parameter measurements using a multimode model, the biases incurred when using a quadrupole-only model to recover full (multimode) signals, and the systematic errors in the imrphenomhm model. We see that the parameters recovered by multimode templates are more precise for all nonzero inclinations as compared to quadrupole templates. For multimode injections, imrphenomd recovers biased parameters for nonzero inclinations with lower likelihood while imrphenomhm-recovered parameters are accurate for most cases, and if a bias exists, it can be explained as a combined effect of observational priors and (in the case of hybrid-NR signals) waveform inaccuracies. However, for cases where imrphenomhm recovers biased parameters, the bias is always significantly smaller than the corresponding imrphenomd recovery, and we conclude that imrphenomhm will be sufficiently accurate to allow unbiased measurements for most gravitational wave observations.

We develop a numerical algorithm for the solution of the Sturm-Liouville differential equation governing the stationary radial oscillations of nonrotating compact stars. Our algorithm is based on the Numerov’s method that turns the Sturm-Liouville differential equation in an eigenvalue problem. In our development, we provide a strategy to correctly deal with the star boundaries and the interfaces between layers with different mechanical properties. Assuming that the fluctuations obey the same equation of state of the background, we analyze various different stellar models and we precisely determine hundreds of eigenfrequencies and of eigenmodes. If the equation of state does not present an interface discontinuity, the fundamental radial eigenmode becomes unstable exactly at the critical central energy density corresponding to the largest gravitational mass. However, in the presence of an interface discontinuity, there exist stable configurations with a central density exceeding the critical one and with a smaller gravitational mass.

There is irresistible observational evidence that binary systems of compact objects with at least one neutron star are progenitors of short gamma-ray bursts, as well as a production site for $r$-process elements, at least when some matter is ejected by the merger and an accretion disk is formed. The recent observations of gravitational waves in conjunction with electromagnetic counterparts fuel the need for models predicting the outcome of a given merger and the properties of the associated matter outflows as a function of the initial parameters of the binary. In this manuscript, we provide updated fitting formulas that estimate the disk mass for double neutron star binaries and ejecta masses for black hole–neutron star and double neutron star binaries, fitted to the results of numerical simulations. Our proposed fitting formulas improve on existing models by aiming for analytical simplicity, by covering a larger region of parameter space, and by accounting for regions of parameter space not covered by numerical simulations but with physically manifest merger outcomes.

Local dwarf spheroidal galaxies (dSphs) are nearby dark-matter dominated systems, making them excellent targets for searching for gamma rays from particle dark matter interactions. If dark matter annihilates or decays directly into two gamma rays (or a gamma ray and a neutral particle), a monochromatic spectral line is created. At TeV energies, no other process is predicted to produce spectral lines, making this a very clean indirect dark matter search channel. With the development of event-by-event energy reconstruction, we can now search for spectral lines with the High Altitude Water Cherenkov (HAWC) Observatory. HAWC is a wide field of view survey instrument located in central Mexico that observes gamma rays from $\sim 200\mathrm{GeV}$ to $\sim 200\mathrm{TeV}$. In this work we present results from a recent search for spectral lines from local, dark matter dominated, dwarf galaxies using 1038 days of HAWC data. We also present updated limits on several continuum channels that were reported in a previous publication. Our gamma-ray spectral line limits are the most constraining obtained so far from 20 TeV to 100 TeV.

We study the basic integral equation in Lindhard’s theory describing the energy given to atomic motion by nuclear recoils in a pure material when the atomic binding energy is taken into account. The numerical solution, which depends only on the slope of the velocity-proportional electronic stopping power and the binding energy, leads to an estimation of the ionization efficiency which is in good agreement with the available experimental measurements for Si and Ge. In this model, the quenching factor for nuclear recoils features a cutoff at an energy equal to twice the assumed binding energy. We argue that the model is a reasonable approximation for Ge even for energies close to the cutoff, while for Si is valid up to recoil energies greater than $\sim 500\mathrm{eV}$.

We study scenarios where loop processes give the dominant contributions to dark matter decay or annihilation despite the presence of tree-level channels. We illustrate this possibility in a specific model where dark matter is part of a hidden sector that communicates with the Standard Model sector via a heavy neutrino portal. We explain the underpinning rationale for how loop processes mediated by the portal neutrinos can parametrically dominate over tree-level decay channels, and we demonstrate that this qualitatively changes the indirect detection signals in positrons, neutrinos, and gamma rays.

The aim of this work is to shed light on some lesser known aspects of Polyakov-loop-extended chiral models (namely, the Polyakov-loop-extended, Nambu–Jona-Lasinio, and quark-meson models), especially on the correlation of the quark sector with the Polyakov loop. We show that the ordering of chiral and Polyakov-loop transitions and their difference in temperature as seen in lattice QCD calculations could be realized with a critical scale of the Polyakov-loop potential that is larger than the one in pure gauge theory. The comparison of the results for the Polyakov-loop susceptibility obtained using the self-consistent medium-dependent quark mass with those obtained while keeping these masses at a fixed value allows us to disentangle chiral-symmetry restoration and center-symmetry breaking effects. Furthermore, a confined chirally restored phase is identified by a plateau in the quark contribution to thermodynamics and by sigma and pion spectral functions that coincide but have a small width. We also discuss that, for some large chemical potential values, the explicit center-symmetry breaking is so strong that statistical deconfinement is realized at infinitely small temperatures. Both the missing sensitivity of the Polyakov loop to the quark mass, except at close to the chiral transition, and the Polyakov loop, being zero at zero temperature at all chemical potentials, can be interpreted as indications of a missing mechanism which accounts for the quark backreaction on the Polyakov loop.

We present a new method of exactly calculating neutrino oscillation probabilities in matter. We leverage the “eigenvector-eigenvalue identity” to show that, given the eigenvalues, all mixing angles in matter follow surprisingly simply. The $CP$ violating phase in matter can then be determined from the Toshev identity. Then, to avoid the cumbersome expressions for the exact eigenvalues, we have applied previously derived perturbative, approximate eigenvalues to this scheme and discovered them to be even more precise than previously realized. We also find that these eigenvalues converge at a rate of 5 orders of magnitude per perturbative order which is the square of the previously realized expectation. Finally, we provide an updated speed versus accuracy plot for oscillation probabilities in matter, to include the methods of this paper.

We have measured new observables based on the final state kinematic imbalances in the mesonless production of ${\nu }_{\mu }+A\to {\mu }^{-}+p+X$ in the MINERνA tracker. Components of the muon-proton momentum imbalances parallel ($\delta p_{\mathrm{Ty}}$) and perpendicular ($\delta p_{\mathrm{Tx}}$) to the momentum transfer in the transverse plane are found to be sensitive to the nuclear effects such as Fermi motion, binding energy, and non-quasielastic (QE) contributions. The QE peak location in $\delta p_{\mathrm{Ty}}$ is particularly sensitive to the binding energy. Differential cross sections are compared to predictions from different neutrino interaction models. The Fermi gas models presented in this study cannot simultaneously describe features such as QE peak location, width, and the non-QE events contributing to the signal process. Correcting the genie’s binding energy implementation according to theory causes better agreement with data. Hints of proton left-right asymmetry are observed in $\delta p_{\mathrm{Tx}}$. Better modeling of the binding energy can reduce the bias in neutrino energy reconstruction, and these observables can be applied in current and future experiments to better constrain nuclear effects.

The response of chiral fermions to time and space dependent axial imbalance and constant magnetic field is analyzed. The axial-vector–vector–vector (AVV) three-point function is studied using a real-time approach at finite temperature in the weak external field approximation. The chiral magnetic conductivity is given analytically for noninteracting fermions. It is pointed out that local charge conservation plays an important role when the axial imbalance is inhomogeneous. Proper regularization is needed which makes the constant axial imbalance limit delicate: for static but spatially oscillating chiral charge the chiral magnetic effect (CME) current vanishes. In the homogeneous (but possible time-dependent) limit of the axial imbalance the CME current is determined solely by the chiral anomaly. As a phenomenological consequence, the observability of the charge asymmetry caused by the CME turns out to be a matter of interplay between various scales of the system. Possible plasma instabilities resulting from the gradient corrections to the CME current are also pointed out.

In this paper, we consider a novel realization of the Dynamical Dark Matter (DDM) framework in which the ensemble of particles which collectively constitute the dark matter are the composite states of a strongly coupled conformal field theory. Cosmological abundances for these states are then generated through mixing with an additional, elementary state. As a result, the physical fields of the DDM dark sector at low energies are partially composite—i.e., admixtures of elementary and composite states. Interestingly, we find that the degree of compositeness exhibited by these states varies across the DDM ensemble. We calculate the masses, lifetimes, and abundances of these states—along with the effective equation of state of the entire ensemble—by considering the gravity dual of this scenario in which the ensemble constituents are realized as the Kaluza-Klein states associated with a scalar propagating within a slice of five-dimensional anti-de Sitter (AdS) space. Surprisingly, we find that the warping of the AdS space gives rise to parameter-space regions in which the decay widths of the dark-sector constituents vary nonmonotonically with their masses. We also find that there exists a maximum degree of AdS warping for which a phenomenologically consistent dark-sector ensemble can emerge. Our results therefore suggest the existence of a potentially rich cosmology associated with partially composite DDM.

In this study, the sensitivity of future lepton colliders to weakly interacting massive particles (WIMP) dark matter is evaluated assuming WIMP pair production accompanied by a photon from initial state radiation, through which the process can be identified. A full detector simulation for the International Large Detector (ILD) concept at the International Linear Collider (ILC) is performed for a center-of-mass energy of 500 GeV. Energy scales of up to 3 TeV can be tested for different effective operators for WIMP masses almost up to half the center-of-mass energy. The sensitivity benefits from the polarized beams, which can reduce the main SM background from neutrino pair production substantially. In addition, systematic uncertainties are shown to be significantly reduced by combining data with several different polarization configurations. In comparison to a previous study, the reconstruction of the forward detectors has been improved, and the systematic uncertainties are fully treated. The results are also extrapolated to other center-of-mass energies, luminosities, and beam polarizations. This allows us to provide results for the full ILC program, i.e., from 250 GeV to 1 TeV, as well as to give approximate results for other planned lepton colliders.

In the present work, we reanalyzed the cross sections for $e^{+}{e}^{-}\to K^{+}{K}^{-}$, where a new structure $X(2240)$ was reported by the BES III collaboration. By including the interference between the direct coupling and vector meson intermediate processes, we find the mass and width of $X(2240)$ are $2197.4\pm 4.4$ and $75.6\pm 7.2\mathrm{MeV}$, respectively, which are well consistent with the Particle Data Group average values of the resonance parameters for $Y(2175)$, thus, we conclude that the $X(2240)$ should be the same state as the $Y(2175)$.

Based on the standard model (SM) of particle physics, we study the decays ${\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\ell }^{+}{\ell }^{-}$ in light of the available inputs from lattice simulations and data from LHCb. We fit the form factors of this decay mode using the available theoretical and experimental inputs after defining different fit scenarios and checking for consistency. The theory inputs include the relations between the form factors in heavy quark effective theory and soft collinear effective theory at the end points of the dilepton invariant mass squared $q^2$. Utilizing the fit results, we predict a few observables related to this mode. We also predict the observable $R_{\mathrm{\Lambda }}=\mathrm{Br}({\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\ell }_i^{+}{\ell }_i^{-})/\mathrm{Br}({\mathrm{\Lambda }}_b\to \mathrm{\Lambda }{\ell }_j^{+}{\ell }_j^{-})$, where ${\ell }_i$ and ${\ell }_j$ are charged leptons of different generations ($i\ne j$). At the moment, we do not observe noticeable differences in the extracted values of the observables in fully data-driven and SM-like fit scenarios.

We continue the study initiated in [P. Betzios, U. Gürsoy, M. Järvinen, and G. Policastro, Phys. Rev. D 97, 081901 (2018).] of the fluctuations of a strongly coupled nonconformal plasma described holographically by Einstein gravity coupled to a dilaton with an exponential potential. The plasma approaches a critical point of a continuous phase transition in a specific limit, where the metric becomes a linear-dilaton background. This results to an analytic description of the quasinormal mode spectrum, that can be extended perturbatively in the deviation away from the critical point. In the previous paper we showed that at criticality the quasinormal frequencies coalesce into a branch cut on the real axis. In this paper we give a more extended and complete discussion of these results. We compare in detail the numerical and analytical approximations in order to confirm their validity; we study (numerically and in a Wentzel-Kramers-Brillouin approximation) the momentum dependence of the modes, in order to determine the crossover scale that limits the validity of the hydrodynamic approximation, and which becomes arbitrarily low at the critical point; and we discuss in detail the procedure we use to complete the theory in the UV by gluing a slice of AdS geometry, and the extent to which it should provide a good approximation to a smooth UV-complete situation.

We present the quantization of the $2+1$ dimensional nonprojectable Hořava theory. The central point of the approach is that this is a theory with second-class constraints, hence the quantization procedure must take account of them. We consider all the terms in the Lagrangian that are compatible with the foliation-preserving-diffeomorphisms symmetry, up to the $z=2$ order which is the minimal order indicated by power-counting renormalizability. The measure of the path integral must be adapted to the second-class constraints, and this has consequences in the quantum dynamics of the theory. Since this measure is defined in terms of Poisson brackets between the second-class constraints, we develop all the Hamiltonian formulation of the theory with the full Lagrangian. We found that the propagator of the lapse function (and the one of the metric) acquires a totally regular form. The quantization requires the incorporation of a Lagrange multiplier for a second-class constraint and fermionic ghosts associated to the measure of the second-class constraints. These auxiliary variables have still nonregular propagators.

We present a formalism that incorporates hydrogen Lyman-alpha ($\mathrm{Ly}\alpha$) polarization arising from the scattering of radiation in galaxy halos into the intensity mapping approach. Using the halo model, and $\mathrm{Ly}\alpha$ emission profiles based on simulations and observations, we calculate auto and cross power spectra at redshifts $3\le z\le 13$ for the $\mathrm{Ly}\alpha$ total intensity, $I$, polarized intensity, $\mathcal{P}$, degree of polarization, $\mathrm{\Pi }=\mathcal{P}/I$, and two new quantities, the astrophysical $E$ and $B$ modes of $\mathrm{Ly}\alpha$ polarization. The one-halo terms of the $\mathrm{\Pi }$ power spectra show a turnover that signals the average extent of the polarization signal, and thus the extent of the scattering medium. The position of this feature depends on redshift, as well as on the specific emission profile shape and extent, in our formalism. Therefore, the comparison of various $\mathrm{Ly}\alpha$ polarization quantities and redshifts can break degeneracies between competing effects, and it can reveal the true shape of the emission profiles, which, in turn, are associated to the physical properties of the cool gas in galaxy halos. Furthermore, measurements of $\mathrm{Ly}\alpha$ $E$ and $B$ modes may be used as probes of galaxy evolution, because they are related to the average degree of anisotropy in the emission and in the halo gas distribution across redshifts. The detection of the polarization signal at $z\sim 3–5$ requires improvements in the sensitivity of current ground-based experiments by a factor of $\sim 10$, and of $\sim 100$ for space-based instruments targeting the redshifts $z\sim 9–10$, the exact values depending on the specific redshift and experiment. Interloper contamination in polarization is expected to be small, because the interlopers need to also be polarized. Overall, $\mathrm{Ly}\alpha$ polarization boosts the amount of physical information retrievable on galaxies and their surroundings, most of it not achievable with total emission alone.

In this work we present the results of a search for continuous gravitational waves from the Galactic Center using LIGO O2 data. The search uses the band-sampled-data directed search pipeline, which performs a semicoherent wide-parameter-space search, exploiting the robustness of the FrequencyHough transform algorithm. The search targets signals emitted by isolated asymmetric spinning neutron stars, located within 25–150 parsecs from the Galactic Center. The frequencies covered in this search range between 10 and 710 Hz with a spin-down range from $-1.8\times {10}^{-9}$ to $3.7\times {10}^{-11}\mathrm{Hz}/\mathrm{s}$. No continuous wave signal has been detected and upper limits on the gravitational wave amplitude are presented. The most stringent upper limit at 95% confidence level, for the Livingston detector, is $\sim 1.4\times {10}^{-25}$ at frequencies near 160 Hz. To date, this is the most sensitive directed search for continuous gravitational-wave signals from the Galactic Center and the first search of this kind using the LIGO second observing run.

In this paper we analyze in detail an $S_3$-symmetric three-Higgs-doublet model with a specific vacuum configuration. This analysis allows us to illustrate important features of models with several Higgs doublets, such as the possibility of having spontaneous $CP$ violation. We start with a real potential and pick a particularly interesting complex vacuum configuration, which does not violate $CP$ before adding soft breaking terms to the potential. We study the role played by different soft symmetry breaking terms. These are essential for our choice of vacuum in order to remove unwanted massless scalars that arise from the spontaneous breaking of an accidental continuous symmetry. We list scalar sector and scalar-gauge sector couplings for the particular case we consider in detail in this work. Results presented in this paper will be useful for model building, in particular for implementations of models with $S_3$ symmetry and spontaneous $CP$ violation, extensions of the fermionic sector with realistic Yukawa couplings and for dark matter studies.