Light sterile neutrinos represent a well-motivated extension of the 3-neutrino paradigm. However, the impressive agreement between standard cosmology and data casts doubts on their existence. Here, we present a class of scenarios that robustly avoids this tension. In these models the sterile neutrinos are light, chiral states of a new sector interacting with the Standard Model via the right-handed neutrino portal, and crucially active-sterile neutrino oscillations require a phase transition in the hidden sector. We explore the hidden-couplings/critical-temperature plane and identify regions where several sterile neutrinos can be accommodated. A late phase transition is usually preferred and may also ward off a potential threat posed by the formation of topologically stable defects.

The $U$-spin symmetry provides a powerful tool to extract the angle $\gamma$ of the Unitarity Triangle and the $B_s^0–{\overline{B}}_s^0$ mixing phase ${\varphi }_s$ from $CP$ violation in the $B_s^0\to K^{-}{K}^{+}$, $B_d^0\to {\pi }^{-}{\pi }^{+}$ system. LHCb has obtained first results with uncertainties at the 7° level. Due to $U$-spin-breaking corrections, it will be challenging to reduce the uncertainty below $\mathcal{O}(5°)$ at Belle II and the LHCb upgrade. We propose a new strategy, using $\gamma$ as input and utilizing $B_s^0\to K^{-}{\ell }^{+}{\nu }_{\ell }$, $B_d^0\to {\pi }^{-}{\ell }^{+}{\nu }_{\ell }$ decays, which allows an extraction of ${\varphi }_s$ with a future theoretical precision of up to $\mathcal{O}(0.5°)$, thereby matching the experimental prospects. Since $B_s^0\to K^{-}{K}^{+}$ is dominated by penguin topologies, new sources of $CP$ violation may be revealed.

We investigate the temperature and magnetic field dependence of the Polyakov loop and heavy quark entropy in a bottom-up Einstein-Maxwell-dilaton (EMD) holographic model for the strongly coupled quark-gluon plasma that quantitatively matches lattice data for the ($2+1$)-flavor QCD equation of state at finite magnetic field and physical quark masses. We compare the holographic EMD model results for the Polyakov loop at zero and nonzero magnetic fields and the heavy quark entropy at vanishing magnetic field with the latest lattice data available for these observables and find good agreement for temperatures $T\gtrsim 150\mathrm{MeV}$ and magnetic fields $eB\lesssim 1{\mathrm{GeV}}^2$. Predictions for the behavior of the heavy quark entropy at nonzero magnetic fields are made that could be readily tested on the lattice.

We put forward the idea that all the theoretically consistent models of gravity have contributions to the observed gravity interaction. In this formulation, each model comes with its own Euclidean path-integral weight where general relativity (GR) has automatically the maximum weight in high-curvature regions. We employ this idea in the framework of Lovelock models and show that in four dimensions the result is a specific form of the $f(R,G)$ model. This specific $f(R,G)$ satisfies the stability conditions and possesses self-accelerating solutions. Our model is consistent with the local tests of gravity since its behavior is the same as in GR for the high-curvature regime. In the low-curvature regime the gravitational force is weaker than in GR, which can be interpreted as the existence of a repulsive fifth force for very large scales. Interestingly, there is an intermediate-curvature regime where the gravitational force is stronger in our model compared to GR. The different behavior of our model in comparison with GR in both low- and intermediate-curvature regimes makes it observationally distinguishable from $\mathrm{\Lambda }\mathrm{CDM}$.

We investigate behaviors of the three-dimensional gravity coupled to a dynamical unit timelike vector, the aether, and present two new classes of exact charged solutions. When $c_{13}=0$, ${\mathrm{\Lambda }}^{\prime }=0$, we find the solution is the usual BTZ black hole but now with a universal horizon. In the frame of black hole chemistry, we then calculate the temperature of the universal horizons and construct the Smarr formulas and first law in the three cases: (quasi)asymptotically flat, aether asymptotically flat, and quasi-BTZ black hole spacetime. We found these universal horizons obey an exact (or slightly modified) first law of black hole mechanics and may have an entropy, and the black hole mass can be interpreted as enthalpy of spacetime. Then the holography may be extended to these horizons under violating Lorentz symmetry.

We study cosmological structure formation with ultralight axion dark matter, or “fuzzy dark matter” (FDM), using a particle-mesh scheme to account for the quantum pressure arising in the Madelung formulation of the Schrödinger-Poisson equations. Subpercent-level energy conservation and correct linear behavior are demonstrated. Whereas the code gives rise to the same core-halo profiles as direct simulations of the Schrödinger equation, it does not reproduce the detailed interference patterns. In cosmological simulations with FDM initial conditions, we find a maximum relative difference of O(10%) in the power spectrum near the quantum Jeans length compared to using a standard $N$-body code with identical initial conditions. This shows that the effect of quantum pressure during nonlinear structure formation cannot be neglected for precision constraints on a dark matter component consisting of ultralight axions.

We calculate the halo correlation function in redshift space using the Gaussian streaming model (GSM). To determine the scale-dependent functions entering the GSM, we use local Lagrangian bias together with convolution Lagrangian perturbation theory (CLPT), which constitutes an approximation to the Post-Zel’dovich approximation. On the basis of $N$-body simulations, we demonstrate that a smoothing of the initial conditions with the Lagrangian radius improves the Zel’dovich approximation and its ability to predict the displacement field of protohalos. Based on this observation, we implement a “truncated” CLPT by smoothing the initial power spectrum and investigate the dependence of the streaming model ingredients on the smoothing scale. We find that the real space correlation functions of halos and their mean pairwise velocity are optimized if the coarse graining scale is chosen to be $1\mathrm{Mpc}/h$ at $z=0$, while the pairwise velocity dispersion is optimized if the smoothing scale is chosen to be the Lagrangian size of the halo. We compare theoretical results for the halo correlation function in redshift space to measurements within the Horizon run 2 $N$-body simulation halo catalog. We find that this simple two-filter smoothing procedure in the spirit of the truncated Zel’dovich approximation significantly improves the $\mathrm{GSM}+\mathrm{CLPT}$ prediction of the redshift space halo correlation function over the whole mass range from large galaxy to galaxy cluster–sized halos. We expect that the necessity for two filter scales is an artifact of our local bias model, and that once a more physical bias model is implemented in CLPT, the only physically relevant smoothing scale will be related to the Lagrangian radius, in accord with our findings based on $N$-body simulations.

In the hope of avoiding model dependence of the cosmological observables, phenomenological parametrizations of cosmic inflation have recently been proposed. Typically, they are expressed in terms of two parameters associated with an expansion of the inflationary quantities matching the belief that inflation is characterized by two numbers only, the tensor-to-scalar ratio and the scalar spectral index. We give different arguments and examples showing that these new approaches are either not generic or insufficient to make predictions at the accuracy level needed by the cosmological data. We conclude that disconnecting inflation from high energy physics and gravity might not be the most promising way to learn about the physics of the early Universe.

We report an isoelectronic test of non-Newtonian forces at micrometer range by sensing the lateral force between a gold sphere and a density modulation source mass using a soft cantilever. Two-dimensional (2D) force mapping, in combination with in situ topographic imaging, is applied to verify the isoelectronic property of the surface. The force signal is found to be electrostatic force dominated, which is correlated with the density modulation structure for thinner gold coating and reduced by thicker gold coating and thermal annealing. Maximum likelihood estimation is used to extract the constraint on the hypothetical force based on the 2D data, and the experiment sets a constraint on the Yukawa type forces without subtraction of the model dependent force background. This result would be a meaningful complementary to previous tests with different methods.

Gravitational wave signals were recently detected directly by LIGO from the coalescences of two stellar mass black hole pairs. These detections have strengthened our long held belief that compact binary coalescences (CBCs) are the most promising gravitational wave detection prospects accessible to ground-based interferometric detectors. For detecting CBC signals, it is of vital importance to characterize and identify non-Gaussian and nonstationary noise in these detectors. In this work, we model two important classes of transient artifacts that contribute to this noise and adversely affect the detector sensitivity to CBC signals. One of them is the sine-Gaussian “glitch,” characterized by a central frequency $f_0$ and a quality factor $Q$ and the other is the chirping sine-Gaussian glitch, which is characterized by $f_0$, $Q$ as well as a chirp parameter. We study the response that a bank of compact binary inspiral templates has to these two families of glitches when they are used to match filter data containing any of these glitches. Two important characteristics of this response are the distributions of the signal-to-noise ratio and the time lag (i.e., how long after the occurrence of a glitch the signal-to-noise ratio of a trigger arises from its matched filtering by a template peaks) of individual templates. We show how these distributions differ from those when the detector data has a real CBC signal instead of a glitch. We argue that these distinctions can be utilized to develop useful signal-artifact discriminators that add negligibly to the computational cost of a CBC search. Specifically, we show how the central frequency of a glitch can be used to set adaptive time windows around it so that any template trigger occurring in that window can be quarantined for further vetting of its supposed astrophysical nature. Second, we recommend focusing efforts on reducing the incidence of glitches with low central-frequency values because they create CBC triggers with the longest time lags. This work allows us to associate such triggers with the glitches that otherwise would have escaped attention.

It has been argued that an extended, quasi-rigid body evolving freely in curved spacetime can deviate from its natural trajectory by simply performing cyclic deformations. More interestingly, in the limit of rapid cycles, the amount of deviation, per cycle, would depend on the sequence of deformations but not on how fast they are performed—like the motion of a swimmer at low Reynolds number. Here, however, we show that the original analysis which supported this idea is inappropriate to investigate the motion of extended bodies in the context of general relativity, rendering its quantitative results invalid and casting doubts on the reality of this swimming effect. We illustrate this by showing that the original analysis leads to a nonzero deviation even in a scenario where no swimming can possibly occur. Notwithstanding, by applying a fully covariant, local formalism, we show that swimming in curved spacetime is indeed possible and that, in general, its magnitude can be of the same order as (fortuitously) anticipated—although it is highly suppressed in the particular scenario where it was originally investigated.

We analyze the possibility that the HESS $\gamma$-ray source at the Galactic center could be explained as the secondary flux produced by annihilation of TeV dark matter (DM) particles with locally enhanced density, in a region spatially compatible with the HESS observations themselves. We study the inner 100 pc considering (i) the extrapolation of several density profiles from state-of-the-art $\mathrm{N}\text{-body}+\text{hydrodynamics}$ simulations of Milky Way-like galaxies, (ii) the DM spike induced by the black hole, and (iii) the DM particles scattering off by bulge stars. We show that in some cases the DM spike may provide the enhancement in the flux required to explain the cutoff in the HESS $\mathrm{J}1745\text{−}290\gamma$-ray spectra as TeV DM. In other cases, it may help to describe the spatial tail reported by HESS II at angular scales $\lesssim 0.54°$ toward $\mathrm{Sgr}{\mathrm{A}}^{*}$.

We introduce an optimal renormalization group analysis pertinent to the analysis of polarization functions associated with the $s$-quark mass relevant in $\tau$-decay. The technique is based on the renormalization group invariance constraints which lead to closed form summation of all the leading and next-to-leading logarithms at each order in perturbation theory. The new perturbation series exhibits reduced sensitivity to the renormalization scale and improved behavior in the complex plane along the integration contour. Using improved experimental and theory inputs, we have extracted the value of the strange quark mass $m_s(2\mathrm{GeV})=106.70\pm 9.36\mathrm{MeV}$ and $m_s(2\mathrm{GeV})=74.47\pm 7.77\mathrm{MeV}$ from presently available ALEPH and OPAL data respectively. These determinations are in agreement with the determinations in other phenomenological methods and from the lattice.

A reanalysis of $\pi \pi$ amplitudes for all important partial waves below about 2 GeV is presented. A set of once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel amplitudes in the $S$, $P$, $D$, and $F$ waves. So far, these specific amplitudes constructed in our works and many other analyses have been fitted only to experimental data and therefore do not fulfill the crossing symmetry condition. In the present analysis, the self-consistent, i.e., unitary and fulfilling the crossing symmetry, amplitudes for the $S$, $P$, $D$, and $F$ waves are formed. The proposed very effective and simple method of modification of the $\pi \pi$ amplitudes does not change their previous original mathematical structure, and the method can be easily applied in various other analyses.

We discuss the Schwinger pair creation process for the system of massless Dirac fermions in the presence of constant external magnetic and electric fields. The pair production rate remains finite unlike the vacuum decay rate. In the recently discovered Dirac semimetals, where the massless Dirac fermions emerge, this pair production may be observed experimentally through the transport properties. We estimate its contribution to the ordinary conductivity of the semimetals.

In this paper, we discuss nonperturbative infrared features of Yang-Mills theory in Euclidean space-time dimensions greater than 4 in the Landau gauge and within the refined Gribov-Zwanziger framework, which enables us to take into account the existence of gauge copies by restricting the domain of integration in the path integral to the Gribov region. Evidences for a decoupling/massive solution for the gluon propagator in higher dimensions are provided. This behavior is strengthened the bigger the dimension is. Further, we show that, by a dimensional reduction of the refined Gribov-Zwanziger action from five to four dimensions, a nonperturbative coupling between the inverse of the Faddeev-Popov operator and the scalar field corresponding to the fifth component of the gauge field naturally arises, being in agreement with the recently proposed mechanism [M. A. L. Capri, M. S. Guimaraes, I. F. Justo, L. F. Palhares, and S. P. Sorella, Phys. Rev. D 90, 085010 (2014).] to generalize the refined Gribov-Zwanziger construction to the matter sector.

In this paper, we present the perturbative evaluation of the difference between the renormalization functions of flavor singlet and nonsinglet bilinear quark operators on the lattice. The computation is performed to two loops and to lowest order in the lattice spacing, for a class of improved lattice actions, including Wilson, tree-level Symanzik and Iwasaki gluons, twisted mass and Stout Link Non-perturbative Clover (SLiNC) Wilson fermions, as well as staggered fermions with twice stout-smeared links. In the staggered formalism, the stout smearing procedure is also applied to the definition of bilinear operators.

We demonstrate that underlying assumptions concerning the structure of constituent parton Fock states in hadrons make a strong impact on the predictions of hadronic interaction models for forward hadron spectra and for long-range correlations between central and forward hadron production. Our analysis shows that combined studies of proton-proton collisions at the Large Hadron Collider by central and forward-looking detectors have a rich potential for discriminating between the main model approaches.

We present a detailed study of the (pseudo)rapidity distributions of massive vector bosons produced in $p+p$ and $p+\mathrm{Pb}$ collisions at the LHC within the next-to-leading order approximation in perturbative quantum chromodynamics. In particular, we discuss the impact of different cold nuclear matter effects on this process using the nuclear parton distributions calculated from the microscopic model developed by Kulagin and Petti (KP). This model was successfully applied to study nuclear effects in the deep-inelastic scattering and the Drell-Yan reactions off various (fixed) target nuclei. Results are compared with the recent CMS and ATLAS $p+\mathrm{Pb}$ data with $\sqrt{s}=5.02\mathrm{TeV}$ per two colliding nucleons. We found an excellent agreement between the predictions of the KP model and the recent LHC data on $W^{\pm }$ and $Z^0$ production in $p+\mathrm{Pb}$ collisions, including the differential cross sections, the forward-backward asymmetries, and $W$ charge asymmetry. We also discuss the sensitivity of the current and future LHC data to the underlying mechanisms responsible for the nuclear modifications of parton density functions.

In this paper, we introduce a new variable $\xi$, namely, the number of tracks associated with the primary vertex, which are not parts of reconstructed objects such as jets, isolated leptons, etc. We demonstrate its usefulness in the context of new physics searches with compressed spectrum in the channel $\text{monojet}+\text{missing}$ transverse momentum (${\cancel{E}}_T$). In models such as in compressed supersymmetry, events are often characterized by a rather large number of soft partons from the cascade decays, none of which results in reconstructed objects. We find that $\xi$, binned in $p_T$, can discriminate these new physics events from events due to $Z+\text{jets}$, that is, the main background in the channel $\text{monojet}+{\cancel{E}}_T$. The information contained in soft tracks is largely uncorrelated with traditional variables such as the effective mass, ${\cancel{E}}_T$, $p_T$ of the jet, etc., and, therefore, can be combined with these to increase the discovery potential by more than 200% (depending on the spectra, of course). In fact we find that simple cuts on $\xi (p_T)$, when combined with cuts on the effective mass, outperforms sophisticated optimized Multivariate Data Analysis using all conventional variables. One can model the background distribution of $\xi (p_T)$ in an entirely data-driven way and make these robust against pileup by identifying the primary vertex.