Most of the information on our cosmos stems from either late-time observations or the imprint of early-time inhomogeneities on the cosmic microwave background. We explore to what extent early modifications of gravity, which become significant after recombination but then decay toward the present, can be constrained by current cosmological observations. For the evolution of the gravitational modification, we adopt the decaying mode of a hybrid metric-Palatini $f(\mathcal{R})$ gravity model which is designed to reproduce the standard cosmological background expansion history and due to the decay of the modification is naturally compatible with Solar System tests. We embed the model in the effective field theory description of Horndeski scalar-tensor gravity with an early-time decoupling of the gravitational modification. Since the quasistatic approximation for the perturbations in the model breaks down at high redshifts, where modifications remain relevant, we introduce a computationally efficient correction to describe the evolution of the scalar field fluctuation in this regime. We compare the decaying early-time modification against geometric probes and recent Planck measurements and find no evidence for such effects in the observations. Current data constrains the scalar field value at $|f_{\mathcal{R}}(z=z_{\mathrm{on}})|\lesssim {10}^{-2}$ for modifications introduced at redshifts $z_{\mathrm{on}}\sim (500–1000)$ with the present-day value $|f_{\mathcal{R}0}|\lesssim {10}^{-8}$. Finally, we comment on constraints that will be achievable with future 21-cm surveys and gravitational wave experiments.

We have investigated a recently proposed halo-based model, Camelus, for predicting weak-lensing peak counts, and compared its results over a collection of 162 cosmologies with those from N-body simulations. While counts from both models agree for peaks with $\mathcal{S}/\mathcal{N}>1$ (where $\mathcal{S}/\mathcal{N}$ is the ratio of the peak height to the r.m.s. shape noise), we find $\approx 50\%$ fewer counts for peaks near $\mathcal{S}/\mathcal{N}=0$ and significantly higher counts in the negative $\mathcal{S}/\mathcal{N}$ tail. Adding shape noise reduces the differences to within 20% for all cosmologies. We also found larger covariances that are more sensitive to cosmological parameters. As a result, credibility regions in the $\{{\mathrm{\Omega }}_m,{\sigma }_8\}$ are $\approx 30\%$ larger. Even though the credible contours are commensurate, each model draws its predictive power from different types of peaks. Low peaks, especially those with $2<\mathcal{S}/\mathcal{N}<3$, convey important cosmological information in N-body data, as shown in previous studies, but Camelus constrains cosmology almost exclusively from high significance peaks $(\mathcal{S}/\mathcal{N}>3)$. Our results confirm the importance of using a cosmology-dependent covariance with at least a 14% improvement in parameter constraints. We identified the covariance estimation as the main driver behind differences in inference, and suggest possible ways to make Camelus even more useful as a highly accurate peak count emulator.

We investigate neutrino flavor transformation in the early Universe in the presence of a lepton asymmetry, focusing on a two-flavor system with 1–3 mixing parameters. We identify five distinct regimes that emerge in an approximate treatment neglecting collisions as the initial lepton asymmetry at high temperature is varied from values comparable to current constraints on the lepton number down to values at which the neutrino-neutrino forward-scattering potential is negligible. The characteristic phenomena occurring in these regimes are (1) large synchronized oscillations, (2) minimal flavor transformation, (3) asymmetric ($\nu$- or $\overline{\nu }$-only) MSW, (4) partial MSW, and (5) symmetric MSW. We examine our numerical results in the framework of adiabaticity, and we illustrate how they are modified by collisional damping. Finally, we point out the existence of matter-neutrino resonances in the early Universe and show that they suffer from nonadiabaticity.

The possibility that the dark matter comprises primordial black holes (PBHs) is considered, with particular emphasis on the currently allowed mass windows at $10^{16}–10^{17}\mathrm{g}$, $10^{20}–10^{24}\mathrm{g}$ and $1–10^3{M}_{\odot }$. The Planck mass relics of smaller evaporating PBHs are also considered. All relevant constraints (lensing, dynamical, large-scale structure and accretion) are reviewed and various effects necessary for a precise calculation of the PBH abundance (non-Gaussianity, nonsphericity, critical collapse and merging) are accounted for. It is difficult to put all the dark matter in PBHs if their mass function is monochromatic but this is still possible if the mass function is extended, as expected in many scenarios. A novel procedure for confronting observational constraints with an extended PBH mass spectrum is therefore introduced. This applies for arbitrary constraints and a wide range of PBH formation models and allows us to identify which model-independent conclusions can be drawn from constraints over all mass ranges. We focus particularly on PBHs generated by inflation, pointing out which effects in the formation process influence the mapping from the inflationary power spectrum to the PBH mass function. We then apply our scheme to two specific inflationary models in which PBHs provide the dark matter. The possibility that the dark matter is in intermediate-mass PBHs of $1–10^3{M}_{\odot }$ is of special interest in view of the recent detection of black-hole mergers by LIGO. The possibility of Planck relics is also intriguing but virtually untestable.

Under the existence of chiral non-Gaussian sources during inflation, the trispectrum of primordial curvature perturbations can break parity. We examine signatures of the induced trispectrum of the cosmic microwave background (CMB) anisotropies. It is confirmed via a harmonic-space analysis that, as a consequence of parity violation, such a CMB trispectrum has nonvanishing signal in the ${\ell }_1+{\ell }_2+{\ell }_3+{\ell }_4=\mathrm{odd}$ domain, which is prohibited in the concordance cosmology. When the curvature trispectrum is parametrized with Legendre polynomials, the CMB signal due to the Legendre dipolar term is enhanced at the squeezed configurations in $\ell$ space, yielding a high signal-to-noise ratio. A Fisher matrix computation results in a minimum detectable size of the dipolar coefficient in a cosmic-variance-limited-level temperature survey as $d_1^{\mathrm{odd}}=640$. In an inflationary model where the inflaton field couples to the gauge field via an $f(\varphi )(F^2+F\tilde{F})$ interaction, the curvature trispectrum contains such a parity-odd dipolar term. We find that, in this model, the CMB trispectrum yields a high signal-to-noise ratio compared with the CMB power spectrum or bispectrum. Therefore, the ${\ell }_1+{\ell }_2+{\ell }_3+{\ell }_4=\mathrm{odd}$ signal could be a promising observable of cosmological parity violation.

The exciting dark matter (XDM) model was proposed as a mechanism to efficiently convert the kinetic energy (in sufficiently hot environments) of dark matter into $\mathrm{e}+\mathrm{e}-$ pairs. The standard scenario invokes a doublet of nearly degenerate dark matter (DM) states and a dark force to mediate a large upscattering cross section between the two. For heavy ($\sim \mathrm{TeV}$) DM, the kinetic energy of weakly interacting massive particles in large (galaxy-sized or larger) halos is capable of producing low-energy positrons. For lighter dark matter, this is kinematically impossible, and the unique observable signature becomes an x-ray line, arising from $\chi \chi \to {\chi }^{*}{\chi }^{*}$, followed by ${\chi }^{*}\to \chi \gamma$. This variant of XDM is distinctive from other DM x-ray scenarios in that its signatures tend to be most present in more massive, hotter environments, such as clusters, rather than nearby dwarfs, and has different dependencies from decaying models. We find that it is capable of explaining the recently reported s-ray line at 3.56 keV. For very long lifetimes of the excited state, primordial decays can explain the signal without the presence of upscattering. Thermal models freeze out as in the normal XDM setup, via annihilations to the light boson $\varphi$. For suitable masses, the annihilation $\chi \chi \to \varphi \varphi$ followed by $\varphi \to \mathrm{SM}$ can explain the reported gamma-ray signature from the Galactic center. Direct detection is discussed, including the possibility of explaining DAMA via the “luminous” dark matter approach. Quite generally, the proximity of the 3.56 keV line to the energy scale of DAMA motivates a reexamination of electromagnetic explanations. Other signals, including lepton jets and the modification of cores of dwarf galaxies are also considered.

We present an analog quantum simulator of spacetimes containing traversable wormholes. A suitable spatial dependence in the external bias of a dc-SQUID array mimics the propagation of light in a 1D wormhole background. The impedance of the array places severe limitations on the type of spacetime that we are able to implement. However, we find that a wormhole throat radius in the submillimeter range is achievable. We show how to modify this spacetime in order to allow the existence of closed timelike curves. The quantum fluctuations of the phase associated to the finite array impedance might be seen as an analog of Hawking’s chronology-protection mechanism.

The evolution equations of anomalous magnetohydrodynamics are derived in the extreme relativistic regime and contrasted with the treatment of hydromagnetic nonlinearities pioneered by Lichnerowicz in the absence of anomalous currents. In particular we explore the situation where the conventional vector currents are complemented by the axial-vector currents arising either from the pseudo-Nambu-Goldstone bosons of a spontaneously broken symmetry or because of finite fermionic density effects. After expanding the generally covariant equations in inverse powers of the conductivity, the relativistic analog of the magnetic diffusivity equation is derived in the presence of vortical and magnetic currents. While the anomalous contributions are generally suppressed by the diffusivity, they are shown to disappear in the perfectly conducting limit. When the flow is irrotational, boost invariant and with vanishing four-acceleration, the corresponding evolution equations are explicitly integrated so that the various physical regimes can be directly verified.

We study the radiative symmetry breaking of $B-L$ in supersymmetric models with an inverse seesaw mechanism. We show that for a wide region of parameter space, the radiative corrections can drive the squared mass of the extra Higgs boson from positive initial values at the GUT scale to negative values at the TeV scale, leading to the spontaneous breaking of the $B-L$ symmetry. We also emphasize that in this class of models, unlike the supersymmetric $B-L$ models with a type-I seesaw, the right-handed sneutrino cannot get a nonzero vacuum expectation value. Therefore, $B-L$ can be radiatively broken, while $R$ parity remains an exact symmetry.

We introduce a class of unified supersymmetric axion theories with unified and Peccei-Quinn (PQ) symmetries broken by the same set of fields at a scale $\sim 2\times 10^{16}\mathrm{GeV}$. A typical domain wall number of order 30 leads to an axion decay constant $f_a$ of order $10^{15}\mathrm{GeV}$. Inflation generates a large saxion condensate, giving a reheat temperature $T_R$ below the QCD scale for supersymmetry breaking of order 1–10 TeV. Axion field oscillations commence in the saxion matter-dominated era near the QCD scale, and recent lattice computations of the temperature dependence of the axion mass in this era allow a controlled calculation of the axion dark matter abundance. The observed abundance can be successfully explained by an initial axion misalignment angle of order unity, ${\theta }_i\sim 1$. A highly correlated set of predictions is discussed for $f_a$, $T_R$, the supersymmetric Higgs mass parameter $\mu$, the amount of dark radiation $\mathrm{\Delta }{N}_{\mathrm{eff}}$, the proton decay rate $\mathrm{\Gamma }(p\to e^{+}{\pi }^0)$, isocurvature density perturbations and the $B$ mode of the cosmic microwave background. The last two are particularly interesting when the energy scale of inflation is also of order $10^{16}\mathrm{GeV}$.

We investigate the masses of $cs\overline{c}\overline{s}$ tetraquark states in a diquark-antidiquark picture employing the relativized quark model proposed by Godfrey and Isgur. Only the antitriplet diquark states in color space are calculated. The diquark masses are obtained with the relativized potential first, and then the diquark and antidiquark are treated as the usual antiquark and quark, respectively, and the masses of the tetraquark states are obtained by solving the Schrödinger equation with the relativized potential between the diquark and antidiquark. The theoretical uncertainties induced by screening effects are also taken into account. It is found that the resonance of $X(4140)$ can be regarded as the $cs\overline{c}\overline{s}$ tetraquark ground states, and the $X(4700)$ can be assigned as the $2S$ excited tetraquark state. When the internal excited diquarks are taken into account, the resonance of $X(4500)$ can be explained as the tetraquark composed of one $2S$ scalar diquark and one scalar antidiquark. In our approach, the $X(4274)$ cannot be explained as a tetraquark state; however, it can be a good candidate of the conventional ${\chi }_{c1}(3{{}^{3}P}_1)$ state. In addition, other charmoniumlike states ${\chi }_{c0}(3915)$, $X(4350)$, $X(4630)$, and $X(4660)$, as the $cs\overline{c}\overline{s}$ tetraquark states, are also discussed.

We present an improvement of the Monte Carlo (MC) event generator Herwiri2, where we recall the latter MC was a prototype for the inclusion of CEEX resummed electroweak (EW) corrections in hadron-hadron scattering at high center of momentum system (cms) energies. In this improvement the new exact $\mathcal{O}({\alpha }^{2}L)$ resummed EW generator $\mathcal{K}\mathcal{K}\mathrm{MC}$ 4.22, featuring as it does the CEEX realization of resummation in the EW sector, is put in union with the Herwig parton shower environment. The Les Houches (LHE) format of the attendant output event file means that all other conventional parton shower environments are available to the would-be user of the resulting new MC. For this reason (and others—see the text) we henceforth refer to the new improvement of the Herwiri2 MC as $\mathcal{K}\mathcal{K}\mathrm{MC}$-hh. Since this new MC features exact $\mathcal{O}(\alpha )$ pure weak corrections from the DIZET EW library and features the CEEX and the EEX YFS-style resummation of large multiple photon effects, it provides already the concrete path to 0.05% precision on such effects if we focus on the EW effects themselves. We therefore show predictions for observable distributions and comparisons with other approaches in the literature. This MC represents an important step in the realization of the exact amplitude-based $\mathrm{QED}\otimes \mathrm{QCD}$ resummation paradigm. Independently of this latter observation, the MC rigorously quantifies important EW effects in the current LHC experiments.

We present a study of the flavor form factors in the framework of a hard-wall AdS/QCD model and compare with the available experimental data. We obtain the flavor form factors by decomposing the Dirac and Pauli form factors for the nucleons using the charge and isospin symmetry. Further, we present a detailed study of the flavor structures of the charge and anomalous magnetization densities in the transverse plane. Both the unpolarized and the transversely polarized nucleons are considered here. We compare the AdS/QCD results with two standard phenomenological parametrizations.

We present a fully differential next-to-next-to-leading-order calculation of $t$-channel single top quark production and decay at the LHC under a narrow-width approximation and neglecting cross talk between incoming protons. We focus on the fiducial cross sections at 13 TeV, finding that the next-to-next-to-leading-order QCD corrections can reach the level of $-6\%$. The scale variations are reduced to the level of a percent. Our results can be used to improve experimental acceptance estimates and the measurements of the single top quark production cross section and the top quark electroweak couplings.

We introduce a general framework for describing deformed phase spaces with group valued momenta. Using techniques from the theory of Poisson-Lie groups and Lie bialgebras we develop tools for constructing Poisson structures on the deformed phase space starting from the minimal input of the algebraic structure of the generators of the momentum Lie group. The tools developed are used to derive Poisson structures on examples of group momentum space much studied in the literature such as the $n$-dimensional generalization of the $\kappa$-deformed momentum space and the $SL(2,\mathbb{R})$ momentum space in three space-time dimensions. We discuss classical momentum observables associated to multiparticle systems and argue that these combine according the usual four-vector addition despite the non-Abelian group structure of momentum space.

We consider a compact Abelian Higgs model in $3+1$ dimensions with a topological axion term and construct its dual theories for both bulk and boundary at strong coupling. The model may be viewed as describing a superconductor with magnetic monopoles, which can also be interpreted as a field theory of a topological Mott insulator. We show that this model is dual to a noncompact topological field theory of particles and vortices. It has exactly the same form as a model for superconducting cosmic strings with an axion term. We consider the duality of the boundary field theory at strong coupling and show that in this case $\theta$ is quantized as $-8\pi n/m$, where $n$ and $m$ are the quantum numbers associated with electric and magnetic charges. These topological states lack a noninteracting equivalent.

Consistent theories of hydrodynamics necessarily include nonhydrodynamic modes, which can be viewed as a regulator necessary to ensure causality. Under many circumstances the choice of regulator is not relevant, but this is not always the case. In particular, for sufficiently small systems (such as those arising in pA or pp collisions) such dependence may be inevitable. We address this issue in the context of the modern version of Müller-Israel-Stewart theory of relativistic hydrodynamics. In this case, by demanding that the nonhydrodynamic modes do not dominate, we find that regulator dependence becomes inevitable only for multiplicities $dN/dY$ of the order of a few. This conclusion supports earlier studies based on hydrodynamic simulations of small systems, at the same time providing a simple physical picture of how hydrodynamics can be reliable even in such seemingly extreme conditions.

We regulate in Euclidean space the Jacobian under scale transformations for two-dimensional nonrelativistic fermions and bosons interacting via contact interactions and compare the resulting scaling anomalies. For fermions, Grassmannian integration inverts the Jacobian; however, this effect is canceled by the regularization procedure and a result similar to that of bosons is attained. We show the independence of the result with respect to the regulating function, and show the robustness of our methods by comparing the procedure with an effective potential method using both cutoff and $\zeta$-function regularization.

Discontinuous Galerkin (DG) methods coupled to weighted essentially nonoscillatory (WENO) algorithms allow high order convergence for smooth problems and for the simulation of discontinuities and shocks. In this work, we investigate WENO-DG algorithms in the context of numerical general relativity, in particular for general relativistic hydrodynamics. We implement the standard WENO method at different orders, a compact (simple) WENO scheme, as well as an alternative subcell evolution algorithm. To evaluate the performance of the different numerical schemes, we study nonrelativistic, special relativistic, and general relativistic test beds. We present the first three-dimensional simulations of general relativistic hydrodynamics, albeit for a fixed spacetime background, within the framework of WENO-DG methods. The most important test bed is a single Tolman-Oppenheimer-Volkoff star in three dimensions, showing that long term stable simulations of single isolated neutron stars can be obtained with WENO-DG methods.

We propose a model of gravity in which a General Relativity metric tensor and an effective metric generated from a single scalar formulated in geometric scalar gravity are mixed. We show that the model yields the exact Schwarzschild solution, along with accelerating behavior of scale factors in cosmological solutions.