Using $N$-body simulations we study the impact of various systematic effects on the low-order moments of the cosmic velocity field: the bulk flow (BF) and the cosmic Mach number (CMN). We consider two types of systematics: those related to survey properties and those induced by the observer’s location in the Universe. In the former category we model sparse sampling, velocity errors, and survey incompleteness (radial and geometrical). In the latter, we consider local group (LG) analogue observers, placed in a specific location within the cosmic web, satisfying various observational criteria. We differentiate such LG observers from Copernican ones, who are at random locations. We report strong systematic effects on the measured BF and CMN induced by sparse sampling, velocity errors and radial incompleteness. For BF most of these effects exceed 10% for scales $R\lesssim 100h^{-1}\mathrm{Mpc}$. For CMN some of these systematics can be catastrophically large (i.e., $>50\%$) also on bigger scales. Moreover, we find that the position of the observer in the cosmic web significantly affects the locally measured BF (CMN), with effects as large as $\sim 20\%$ ($30\%$) at $R\lesssim 50h^{-1}\mathrm{Mpc}$ for a LG-like observer as compared to a random one. This effect is comparable to the sample variance at the same scales. Such location-dependent effects have not been considered previously in BF and CMN studies and here we report their magnitude and scale for the first time. To highlight the importance of these systematics, we additionally study a model of modified gravity with $\sim 15\%$ enhanced growth rate (compared to general relativity). We found that the systematic effects can mimic the modified gravity signal. The worst-case scenario is realized for a case of a LG-like observer, when the effects induced by local structures are degenerate with the enhanced growth rate fostered by modified gravity. Our results indicate that dedicated constrained simulations and realistic mock galaxy catalogs will be absolutely necessary to fully benefit from the statistical power of the forthcoming peculiar velocity data from surveys such as TAIPAN, WALLABY, COSMICFLOWS-4 and SKA.

The theory of inflation is one of the fundamental and revolutionary developments of modern cosmology that became able to explain many issues of the early Universe in the context of the standard cosmological model (SCM). However, the initial singularity of the Universe, where physics is indefinite, is still obscure in the combined $\mathrm{SCM}+\mathrm{inflation}$ scenario. An alternative to $\mathrm{SCM}+\mathrm{inflation}$ without the initial singularity is thus always welcome, and bouncing cosmology is an attempt at that. The current work is thus motivated to investigate the bouncing solutions in modified gravity theories when the background universe is described by the spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) geometry. We show that the simplest way to obtain the bouncing cosmologies in such spacetime is to consider some kind of Lagrangian whose gravitational sector depends only on the square of the Hubble parameter of the FLRW universe. For these modified Lagrangians, the corresponding Friedmann equation, a constraint in the dynamics of the Universe, depicts a curve in the phase space $(H,\rho )$, where $H$ is the Hubble parameter and $\rho$ is the energy density of the Universe. As a consequence, a bouncing cosmology is obtained when this curve is closed and crosses the axis $H=0$ at least twice, and whose simplest particular example is the ellipse depicting the well-known holonomy corrected Friedmann equation in loop quantum cosmology (LQC). Sometimes, a crucial point in such theories is the appearance of the Ostrogradski instability at the perturbative level; however, fortunately enough, in the present work, as long as the linear level of perturbations is concerned, this instability does not appear, although it may appear at the higher order of perturbations.

The Horndeski scalar-tensor theory and its recent extensions allow nonlinear derivative interactions of the scalar degree of freedom. We study the matter bispectrum of large scale structure as a probe of these modified gravity theories, focusing in particular on the effect of the terms that newly appear in the so-called “beyond Horndeski” theories. We derive the second-order solution for the matter density perturbations and find that the interactions beyond Horndeski lead to a new time-dependent coefficient in the second-order kernel which differs in general from the standard value of general relativity and the Horndeski theory. This can deform the matter bispectrum at the folded triangle configurations ($k_1+k_2=k_3$), while it is never possible within the Horndeski theory.

We describe scalar-bimetric theories where the dynamics of the Universe are governed by two separate metrics, each with an Einstein-Hilbert term. In this setting, the baryonic and dark matter components of the Universe couple to metrics which are constructed as functions of these two gravitational metrics. More precisely, the two metrics coupled to matter are obtained by a linear combination of their vierbeins, with scalar-dependent coefficients. The scalar field, contrary to dark-energy models, does not have a potential of which the role is to mimic a late-time cosmological constant. The late-time acceleration of the expansion of the Universe can be easily obtained at the background level in these models by appropriately choosing the coupling functions appearing in the decomposition of the vierbeins for the baryonic and dark matter metrics. We explicitly show how the concordance model can be retrieved with negligible scalar kinetic energy. This requires the scalar coupling functions to show variations of order unity during the accelerated expansion era. This leads in turn to deviations of order unity for the effective Newton constants and a fifth force that is of the same order as Newtonian gravity, with peculiar features. The baryonic and dark matter self-gravities are amplified although the gravitational force between baryons and dark matter is reduced and even becomes repulsive at low redshift. This slows down the growth of baryonic density perturbations on cosmological scales, while dark matter perturbations are enhanced. These scalar-bimetric theories have a perturbative cutoff scale of the order of 1 AU, which prevents a precise comparison with Solar System data. On the other hand, we can deduce strong requirements on putative UV completions by analyzing the stringent constraints in the Solar System. Hence, in our local environment, the upper bound on the time evolution of Newton’s constant requires an efficient screening mechanism that both damps the fifth force on small scales and decouples the local value of Newton constant from its cosmological value. This cannot be achieved by a quasistatic chameleon mechanism and requires going beyond the quasistatic regime and probably using derivative screenings, such as Kmouflage or Vainshtein screening, on small scales.

Weak lensing maps contain information beyond two-point statistics on small scales. Much recent work has tried to extract this information through a range of different observables or via nonlinear transformations of the lensing field. Here we train and apply a two-dimensional convolutional neural network to simulated noiseless lensing maps covering 96 different cosmological models over a range of $\{{\mathrm{\Omega }}_m,{\sigma }_8\}$. Using the area of the confidence contour in the $\{{\mathrm{\Omega }}_m,{\sigma }_8\}$ plane as a figure of merit, derived from simulated convergence maps smoothed on a scale of 1.0 arcmin, we show that the neural network yields $\approx 5\times$ tighter constraints than the power spectrum, and $\approx 4\times$ tighter than the lensing peaks. Such gains illustrate the extent to which weak lensing data encode cosmological information not accessible to the power spectrum or even other, non-Gaussian statistics such as lensing peaks.

As recently pointed out in [Phys. Rev. D 96, 083502 (2017)] the evolution of the linear matter perturbations in nonadiabatic dynamical dark energy models is almost indistinguishable (quasidegenerated) to the standard $\mathrm{\Lambda }\mathrm{CDM}$ scenario. In this work we extend this analysis to CMB observables in particular the integrated Sachs-Wolfe effect and its cross-correlation with large scale structure. We find that this feature persists for such CMB related observable reinforcing that new probes and analysis are necessary to reveal the nonadiabatic features in the dark energy sector.

The combined observation of GW170817 and its electromagnetic counterpart GRB170817A reveals that gravitational waves propagate at the speed of light in high precision. We apply the standard analysis of cosmological perturbations, as well as the effective field theory approach, to investigate the experimental consequences for the theory of $f(T)$ gravity. Our analysis verifies for the first time that the speed of gravitational waves within $f(T)$ gravity is equal to the light speed, and hence, the constraints from GW170817 and GRB170817A are trivially satisfied. Nevertheless, by examining the dispersion relation and the frequency of cosmological gravitational waves, we observe a deviation from the results of general relativity, quantified by a new parameter. Although its value is relatively small in viable $f(T)$ models, its possible future measurement in advancing gravitational-wave astronomy would be the smoking gun of testing this type of modified gravity.

Cosmic rays are an important tool to study dark matter (DM) annihilation in our Galaxy. Recently, a possible hint for dark matter annihilation was found in the antiproton spectrum measured by AMS-02, even though the result might be affected by theoretical uncertainties. A complementary way to test its dark matter interpretation would be the observation of low-energy antinuclei in cosmic rays. We determine the chances to observe antideuterons with GAPS and AMS-02 and the implications for the ongoing AMS-02 antihelium searches. We find that the corresponding antideuteron signal is within the GAPS and AMS-02 detection potential. If, more conservatively, the putative signal was considered as an upper limit on DM annihilation, our results would indicate the highest possible fluxes for antideuterons and antihelium compatible with current antiproton data.

If any violation of Lorentz symmetry exists in the hadron sector, its ultimate origins must lie at the quark level. We continue the analysis of how the theories at these two levels are connected, using chiral perturbation theory. Considering a 2-flavor quark theory, with dimension-4 operators that break Lorentz symmetry, we derive a low-energy theory of pions and nucleons that is invariant under local chiral transformations and includes the coupling to external fields. The pure meson and baryon sectors, as well as the couplings between them and the couplings to external electromagnetic and weak gauge fields, contain forms of Lorentz violation which depend on linear combinations of quark-level coefficients. In particular, at leading order the electromagnetic couplings depend on the very same combinations as appear in the free particle propagators. This means that observations of electromagnetic processes involving hadrons—such as vacuum Cerenkov radiation, which may be allowed in Lorentz-violating theories—can only reliably constrain certain particular combinations of quark coefficients.

We examine the capabilities of the DUNE experiment as a probe of the neutrino mixing paradigm. Taking the current status of neutrino oscillations and the design specifications of DUNE, we determine the experiment’s potential to probe the structure of neutrino mixing and $CP$ violation. We focus on the poorly determined parameters ${\theta }_{23}$ and ${\delta }_{CP}$ and consider both two and seven years of run. We take various benchmarks as our true values, such as the current preferred values of ${\theta }_{23}$ and ${\delta }_{CP}$, as well as several theory-motivated choices. We determine quantitatively DUNE’s potential to perform a precision measurement of ${\theta }_{23}$, as well as to test the $CP$ violation hypothesis in a model-independent way. We find that, after running for seven years, DUNE will make a substantial step in the precise determination of these parameters, bringing to quantitative test the predictions of various theories of neutrino mixing.

The two-Higgs-doublet model (2HDM) provides an excellent benchmark to study physics beyond the Standard Model (SM). In this work, we discuss how the behavior of the model at high-energy scales causes it to have a scalar with properties very similar to those of the SM—which means the 2HDM can be seen to naturally favor a decoupling or alignment limit. For a type II 2HDM, we show that requiring the model to be theoretically valid up to a scale of 1 TeV, by studying the renormalization group equations (RGE) of the parameters of the model, causes a significant reduction in the allowed magnitude of the quartic couplings. This, combined with $B$-physics bounds, forces the model to be naturally decoupled. As a consequence, any nondecoupling limits in type II, like the wrong-sign scenario, are excluded. On the contrary, even with the very constraining limits for the Higgs couplings from the LHC, the type I model can deviate substantially from alignment. An RGE analysis similar to that made for type II shows, however, that requiring a single scalar to be heavier than about 500 GeV would be sufficient for the model to be decoupled. Finally, we show that the 2HDM is stable up to the Planck scale independently of which of the $CP$-even scalars is the discovered 125 GeV Higgs boson.

The three-particle $N\pi \pi$ state contribution to the QCD two-point function of standard nucleon interpolating fields is computed to leading order in chiral perturbation theory. Using the experimental values for two low-energy coefficients, the impact of this contribution on lattice QCD calculations of the nucleon mass is estimated. The impact is found to be at the per mille level at most and negligible in practice.

We revisit the line of nonunitary theories that interpolate between the Virasoro minimal models. Numerical bootstrap applications have brought about interest in the four-point function involving the scalar primary of lowest dimension. Using recent progress in harmonic analysis on the conformal group, we prove the conjecture that global conformal blocks in this correlator appear with positive coefficients. We also compute many such coefficients in the simplest mixed correlator system. Finally, we comment on the status of using global conformal blocks to isolate the truly unitary points on this line.

Analogous to the work of hidden charm molecular pentaquarks, we study possible hidden strange molecular pentaquarks composed of $\mathrm{\Sigma }$ (or ${\mathrm{\Sigma }}^{*}$) and $K$ (or $K^{*}$) in the framework of a quark delocalization color screening model. Our results suggest that the $\mathrm{\Sigma }K$, $\mathrm{\Sigma }{K}^{*}$, and ${\mathrm{\Sigma }}^{*}{K}^{*}$ with $I{J}^P=\frac{1}{2}{\frac{1}{2}}^{-}$ and $\mathrm{\Sigma }{K}^{*}$, ${\mathrm{\Sigma }}^{*}K$, and ${\mathrm{\Sigma }}^{*}{K}^{*}$ with $I{J}^P=\frac{1}{2}{\frac{3}{2}}^{-}$ are all resonance states by coupling the open channels. The molecular pentaquark ${\mathrm{\Sigma }}^{*}K$ with quantum numbers $I{J}^P=\frac{1}{2}{\frac{3}{2}}^{-}$ can be seen as a strange partner of the LHCb $P_c(4380)$ state. The possibility of identifying the resonances as nucleon resonances is proposed.

We perform the investigation of two-body hidden-bottom transitions of the $\mathrm{\Upsilon }(6S)$, which include $\mathrm{\Upsilon }(6S)\to \mathrm{\Upsilon }(1^3{D}_J)\eta (J=1,2,3)$ decays. For estimating the branching ratios of these processes, we consider contributions from the triangle hadronic loops composed of $S$-wave $B_{(s)}$ and $B_{(s)}^{*}$ mesons, which are a bridge to connect the $\mathrm{\Upsilon }(6S)$ and final states. Our results show that both of the branching ratios of these decays can reach ${10}^{-3}$. Because of such considerable potential to observe these two-body hidden-bottom transitions of the $\mathrm{\Upsilon }(6S)$, we suggest the forthcoming Belle II experiment to explore them.

It is shown that explicitly broken scale symmetry is essential for dense skyrmion matter in hidden local symmetry theory. Consistency with the vector manifestation fixed point for the hidden local symmetry of the lowest-lying vector mesons and the dilaton limit fixed point for scale symmetry in dense matter is found to require that the anomalous dimension ($|{\gamma }_{G^2}|$) of the gluon field strength tensor squared ($G^2$) that represents the quantum trace anomaly should be $1.0\lesssim |{\gamma }_{G^2}|\lesssim 3.5$. The magnitude of $|{\gamma }_{G^2}|$ estimated here will be useful for studying hadron and nuclear physics based on the scale-chiral effective theory. More significantly, that the dilaton limit fixed point can be arrived at with ${\gamma }_{G^2}\ne 0$ at some high density signals that scale symmetry can arise in dense medium as an “emergent” symmetry.

The relatively large value of the neutrino mixing angle ${\theta }_{13}$ set by recent measurements allows us to use solar neutrinos to set a limit on the neutrino magnetic moment involving the second and third flavor families, ${\mu }_{23}$. The existence of a random magnetic field in the solar convective zone can produce a significant antineutrino flux when a nonvanishing neutrino magnetic moment is assumed. Even if we consider a vanishing neutrino magnetic moment involving the first family, electron antineutrinos are indirectly produced through the mixing between the first and third families and ${\mu }_{23}\ne 0$. Using KamLAND limits on the solar flux of electron antineutrino, we set the limit ${\mu }_{23}<0.95\times {10}^{-11}{\mu }_B$ as a reasonable assumption on the behavior of solar magnetic fields. This is the first time that a limit on ${\mu }_{23}$ has been established in the literature directly from neutrino interactions with magnetic fields, and, interestingly enough, is comparable with the limits on the neutrino magnetic moment involving the first family and with the ones coming from modifications to the electroweak cross section.

We present a study of the $X^{\pm }(5568)$ using semileptonic decays of the $B_s^0$ meson using the full run II integrated luminosity of $10.4{\mathrm{fb}}^{-1}$ in proton-antiproton collisions at a center of mass energy of 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. We report evidence for a narrow structure, $X^{\pm }(5568)$, in the decay sequence $X^{\pm }(5568)\to B_s^0{\pi }^{\pm }$ where $B_s^0\to {\mu }^{\mp }{D}_s^{\pm }\mathrm{X}$, $D_s^{\pm }\to \varphi {\pi }^{\pm }$ which is consistent with the previous measurement by the D0 Collaboration in the hadronic decay mode, $X^{\pm }(5568)\to B_s^0{\pi }^{\pm }$ where $B_s^0\to J/\psi \varphi$. The mass and width of this state are measured using a combined fit of the hadronic and semileptonic data, yielding $m={5566.9}_{-3.1}^{+3.2}{(\mathrm{stat})}_{-1.2}^{+0.6}(\mathrm{syst})\mathrm{MeV}/c^2$, $\mathrm{\Gamma }={18.6}_{-6.1}^{+7.9}{(\mathrm{stat})}_{-3.8}^{+3.5}(\mathrm{syst})\mathrm{MeV}/c^2$ with a significance of $6.7\sigma$.