In this paper, we study the local observational consequences of a violation of the Einstein equivalence principle induced by models of light scalar dark matter (DM). We focus on two different models where the scalar field couples linearly or quadratically to the standard model of matter fields. For both these cases, we derive the solutions of the scalar field. We also derive from first principles the expressions for two types of observables: (i) the local comparison of two atomic sensors that are differently sensitive to the constants of nature, and (ii) the local differential acceleration between two test masses with different compositions. For the linear coupling, we recover that the signatures induced by DM on both observables are the sum of harmonic and Yukawa terms. For the quadratic coupling, on the other hand, the signatures derived for both types of observables turn out to be the sum of a time-independent term and a harmonic oscillation, whose amplitudes both depend on the position. Such behavior is new and can make experiments in space more sensitive than terrestrial ones. Besides this, the observables present some interesting nonlinear behaviors that are due to the amplification or to the screening of the scalar field, depending on the parameters of the theory, and on the compactness of the source of the gravitational field. Finally, we infer the various limits on the DM coupling parameters by using existing frequency comparisons on the one hand and tests of the universality of free fall on the ground (torsion balances) or in space (MICROSCOPE mission) on the other hand. We show that in the quadratic case, so-called natural parameters are still allowed by observations.

The Janis-Newman-Winicour and Papapetrou metrics represent counterparts to the Schwarzschild black hole with scalar and antiscalar background fields, correspondingly (where “anti” is to be understood as in “anti–de Sitter”). There is also a scalar counterpart (the Krori-Bhattacharjee metric) to the Kerr black hole. Here we study analytical connections between these solutions and obtain the exact rotational generalization of the antiscalar Papapetrou spacetime as a viable alternative to the Kerr black hole. The antiscalar metrics appear to be the simplest ones as they do not reveal event horizons and ergospheres, and they do not involve an extra parameter for scalar charge. Static antiscalar field is thermodynamically stable and self-consistent, but this is not the case for the scalar Janis-Newman-Winicour solution; in addition, antiscalar thermodynamics is reducible to black-hole thermodynamics. Lensing, geodetic, and Lense-Thirring effects are found to be practically indistinguishable between antiscalar and vacuum solutions in weak fields. Only strong-field observations might provide a test for the existence of antiscalar background. In particular, the antiscalar solution predicts 5% larger shadows of supermassive compact objects, as compared to the vacuum solution. Another measurable aspect is the 6.92% difference in the frequency of the innermost stable circular orbit characterizing the upper cutoff in the gravitational wave spectrum.

The $U(1{)}_{B-L}$ gauge symmetry is a promising extension of the standard model of particle physics, which is supposed to be broken at some high energy scale. Associated with the $U(1{)}_{B-L}$ gauge symmetry breaking, right-handed neutrinos acquire their Majorana masses and then tiny light neutrino masses are generated through the seesaw mechanism. In this paper, we demonstrate that the first-order phase transition of the $U(1{)}_{B-L}$ gauge symmetry breaking can generate a large amplitude of stochastic gravitational wave (GW) radiation for some parameter space of the model, which is detectable in future experiments. Therefore, the detection of GWs is an interesting strategy to probe the seesaw scale which can be much higher than the energy scale of collider experiments.

Finite size effects in a neutron star merger are manifested, at leading order, through the tidal deformabilities of the stars. If strong first-order phase transitions do not exist within neutron stars, both neutron stars are described by the same equation of state, and their tidal deformabilities are highly correlated through their masses even if the equation of state is unknown. If, however, a strong phase transition exists between the central densities of the two stars, so that the more massive star has a phase transition and the least massive star does not, this correlation will be weakened. In all cases, a minimum deformability for each neutron star mass is imposed by causality, and a less conservative limit is imposed by the unitary gas constraint, both of which we compute. In order to make the best use of gravitational wave data from mergers, it is important to include the correlations relating the deformabilities and the masses as well as lower limits to the deformabilities as a function of mass. Focusing on the case without strong phase transitions, and for mergers where the chirp mass $\mathcal{M}\le 1.4M_{\odot }$, which is the case for all observed double neutron star systems where a total mass has been accurately measured, we show that the ratio of the dimensionless tidal deformabilities satisfy ${\mathrm{\Lambda }}_1/{\mathrm{\Lambda }}_2\sim q^6$, where $q=M_2/M_1$ is the binary mass ratio; $\mathrm{\Lambda }$ and $M$ are the dimensionless deformability and mass of each star, respectively. Moreover, they are bounded by $q^{n_{-}}\ge {\mathrm{\Lambda }}_1/{\mathrm{\Lambda }}_2\ge q^{n_{0+}+q{n}_{1+}}$, where $n_{-}<n_{0+}+q{n}_{1+}$; the parameters depend only on $\mathcal{M}$, which is accurately determined from the gravitational-wave signal. We also provide analytic expressions for the wider bounds that exist in the case of a strong phase transition. We argue that bounded ranges for ${\mathrm{\Lambda }}_1/{\mathrm{\Lambda }}_2$, tuned to $\mathcal{M}$, together with lower bounds to $\mathrm{\Lambda }(M)$, will be more useful in gravitational waveform modeling than other suggested approaches.

The solar disk is a bright source of multi-GeV gamma rays, due to the interactions of hadronic cosmic rays with the solar atmosphere. However, the underlying production mechanism is not understood, except that its efficiency must be greatly enhanced by magnetic fields that redirect some cosmic rays from ingoing to outgoing before they interact. To elucidate the nature of this emission, we perform a new analysis of solar atmospheric gamma rays with 9 years of Fermi-LAT data, which spans nearly the full 11-year solar cycle. We detect significant gamma-ray emission from the solar disk from 1 GeV up to $\gtrsim 200\mathrm{GeV}$. The overall gamma-ray spectrum is much harder ($\sim E_{\gamma }^{-2.2}$) than the cosmic-ray spectrum ($\sim E_{\mathrm{CR}}^{-2.7}$). We find a clear anticorrelation between the solar cycle phase and the gamma-ray flux between 1 and 10 GeV. Surprisingly, we observe a spectral dip between $\sim 30$ and 50 GeV in an otherwise power-law spectrum. This was not predicted, is not understood, and may provide crucial clues to the gamma-ray emission mechanism. The flux above 100 GeV, which is brightest during the solar minimum, poses exciting opportunities for HAWC, LHAASO, IceCube, and KM3NeT.

Recent observations have detected extended TeV $\gamma$-ray emission surrounding young and middle-aged pulsars. The morphology of these “TeV halos” requires cosmic-ray diffusion to be locally suppressed by a factor of $\sim 100–1000$ compared to the typical interstellar medium. No model currently explains this suppression. We show that cosmic-ray self-confinement can significantly inhibit diffusion near pulsars. The steep cosmic-ray gradient generates Alfvén waves that resonantly scatter the same cosmic-ray population, suppressing diffusion within $\sim 20\mathrm{pc}$ of young pulsars ($\lesssim 100\mathrm{kyr}$). In this model, TeV halos evolve through two phases, a growth phase where Alfvén waves are resonantly generated and cosmic-ray diffusion becomes increasingly suppressed, and a subsequent relaxation phase where the diffusion coefficient returns to the standard interstellar value. Intriguingly, cosmic rays are not strongly confined early in the TeV halo evolution, allowing a significant fraction of injected $e^{\pm }$ to escape. If these $e^{\pm }$ also escape from the surrounding supernova remnant, they would provide a natural explanation for the positron excess observed by PAMELA and AMS-02. Recently created TeV cosmic rays are confined in the TeV halo, matching observations by HAWC and H.E.S.S. While our default model relaxes too rapidly to explain the confinement of TeV cosmic rays around mature pulsars, such as Geminga, models utilizing a Kraichnan turbulence spectrum experience much slower relaxation. Thus, observations of TeV halos around mature pulsars may provide a probe into our understanding of interstellar turbulence.

We consider charged anti–de Sitter planar black holes in the four-dimensional Einstein-Maxwell-Horndeski theory with two free axions and analyze the black hole thermodynamics. We calculate the holographic thermoelectric conductivities of the dual field theory and determine the ratio of thermal conductivity over the temperature. At low temperature and with zero electric current, we find that the ratio is proportional to temperature squared and hence can be arbitrarily small, providing the first example that violates the previously conjectured thermal conductivity bound.

With increasing temperatures, Schwinger pair production changes from a quantum tunneling to a classical, thermal process, determined by a worldline sphaleron. We show this and calculate the corresponding rate of pair production for both spinor and scalar quantum electrodynamics, including the semiclassical prefactor. For electron-positron pair production from a thermal bath of photons and in the presence of an electric field, the rate we derive is faster than both perturbative photon fusion and the zero temperature Schwinger process. We work to all-orders in the coupling and hence our results are also relevant to the pair production of (strongly coupled) magnetic monopoles in heavy-ion collisions.

We construct a texture where the seesaw matrix is diagonalized by the tribimaximal (TBM) matrix with a phase. All angles of the Cabibbo-Kobayashi-Maskawa matrix and Pontecorvo-Maki-Nakagawa-Sakata matrix are consistent with particle data group values, and the mass relations of quarks and charged leptons extrapolated to the grand unified theory scale are satisfied, including the Gatto relation. The novel ingredient is the asymmetry of the down-quark and charged lepton Yukawa matrices. Explaining the reactor angle requires a $\cancel{\mathrm{CP}}$ phase in the TBM matrix, resulting in the Jarlskog-Greenberg invariant at $|J|=0.028$, albeit with an undetermined sign. While $SO(10)$ restrains the right-handed neutrino Majorana matrix, the neutrino masses are left undetermined.

We calculate the scalar and tensor charges of the nucleon in $2+1$-flavor lattice QCD, for which the systematics of the renormalization of the disconnected diagram is well controlled. Numerical simulations are performed at a single lattice spacing $a=0.11\mathrm{fm}$. We simulate four pion masses, which cover a range of $m_{\pi }\sim 290–540\mathrm{MeV}$, and a single strange quark mass close to its physical value. The statistical accuracy is improved by employing the so-called low-mode averaging technique and the truncated solver method. We study up, down, and strange quark contributions to the nucleon charges by calculating disconnected diagrams using the all-to-all quark propagator. Chiral symmetry is exactly preserved by using the overlap quark action to avoid operator mixing among different flavors, which complicates the renormalization of scalar and tensor matrix elements and leads to possibly large contamination to the small strange quark contributions. We also study the nucleon axial charge with a contribution from the disconnected diagram. Our results are in reasonable agreement with experiments and previous lattice studies.

In this paper, the temperature dependence of the $SU(3)$ gluodynamics bulk viscosity is studied within lattice simulations. To carry out this study, we measure the correlation function of the trace of the energy-momentum tensor for a set of temperatures within the range $T/T_c\in (0.9,1.5)$. To extract the bulk viscosity from the correlation function, we apply the Backus-Gilbert method and the Tikhonov regularization method. We show that the ratio $\zeta /s$ is small in the region $T/T_c\ge 1.1–1.2$, and in the vicinity of the transition $T/T_c\le 1.1–1.2$ it quickly rises. Our results are in agreement with previous lattice studies and in a reasonable agreement with other phenomenological approaches. Obtained values of the bulk viscosity are significantly larger than perturbative results, which confirms that quark-gluon plasma is a strongly correlated system.

Using realistic quark propagators and meson Bethe-Salpeter amplitudes based on the Dyson-Schwinger equations, we calculate the pion and kaon’s valence parton distribution functions (PDF) through the modified impulse approximation. The PDFs we obtained at hadronic scale have the purely valence characteristic and exhibit both dynamical chiral symmetry breaking and $SU(3)$ flavor symmetry breaking effects. A new calculation technique is introduced to determine the valence PDFs with precision. Through next-to-leading order (NLO) evolution, our result is compared with pion and kaon valence PDF data at experimental scale. Good agreement is found in the case of pion, while deviation emerges for kaon. We point out this situation can potentially be resolved by incorporating gluon contributions into the mesons if the pion hosts more gluons than kaon nonperturbatively.

In this paper we reexamine the possibility of extracting parton distribution functions from lattice simulations. We discuss the case of quasiparton distribution functions, the possibility of using the reduced Ioffe-time distributions and the more recent proposal of directly making reference to the computation of the current-current $T$-product. We show that in all cases the process of renormalization hindered by the lattice momenta limitation represents an obstruction to a direct Euclidean calculation of the parton distribution function.

We study chiral symmetry breaking in the Nambu–Jona-Lasinio model regularized in proper time in arbitrary spacetime dimensions through an iterative procedure by writing the gap equation in the form of a discrete dynamical system with the coupling constant as the control parameter. Expectedly, we obtain the critical coupling for chiral symmetry breaking when a nontrivial solution bifurcates away from the trivial one and becomes an attractor. By increasing further the value of the coupling constant, we observe a second bifurcation where the dynamical solution is no longer an attractor, and observation that holds true in all spacetime dimensions. In the superstrong coupling regime, the system becomes chaotic.

Theoretical and phenomenological predictions of $\mathcal{BR}(K_L\to ({\mu }^{+}{\mu }^{-})\gamma )\sim 7\times {10}^{-13}$ are presented for different model form factors $F_{K_L\gamma {\gamma }^{*}}(Q^2)$. These rates are comparable to existing and near-term rare $K_L$ decay searches at J-PARC and CERN, indicating a discovery of true muonium is possible. Further discussion of potential backgrounds is made.

We include $pp\to p{\mathrm{\Delta }}^{+}{\mu }^{+}{\mu }^{-}$ and $pp\to {\mathrm{\Delta }}^{+}{\mathrm{\Delta }}^{+}{\mu }^{+}{\mu }^{-}$ processes in addition to the standard $pp\to pp{\mu }^{+}{\mu }^{-}$ process both in equivalent-photon approximation (EPA) and in exact $2\to 4$ calculations. For comparison we calculate also the continuum proton dissociation in a recently developed $k_t$-factorization approach to $\gamma \gamma$-involved processes with parametrizations of $F_2$ structure function known from the literature. The calculated cross section including all the processes is considerably larger than the one measured recently by the ATLAS collaboration. We calculate absorption effects for $pp\to pp{\mu }^{+}{\mu }^{-}$ process in the momentum space. The final cross section with absorption effects is by 10% larger than the one measured by the ATLAS collaboration which is difficult to explain. Several differential distributions with the ATLAS experimental cuts are presented. It is shown that the processes with electromagnetic $p\to \mathrm{\Delta }(1232)$ and $p\to N(1440)$ transitions, that have similar characteristics as the $pp\to pp{\mu }^{+}{\mu }^{-}$ process, increase the cross section for ${\mu }^{+}{\mu }^{-}$ production and thus can affect its theoretical interpretation when the leading baryons are not detected as is the case for the CMS and ATLAS measurements. The mechanism of dissociation into hadronic continuum is not under full control as the corresponding absorption effects are not fully understood. We present first predictions for future ATLAS experiment with the ALFA subdetectors and discuss observables relevant for this measurement.

We study the sensitivity of certain observables to the anomalous right tensorial coupling in single top production at the LHC at $\sqrt{s}=13\mathrm{TeV}$. The observables consist of asymmetries constructed from the energy and angles of the decay products of the top quark produced in single top production through the $t$-channel. The computation is done at leading order (LO) and next-to-leading order (NLO) in the strong coupling in the five-flavor scheme. We have estimated projected limits on the anomalous coupling, both at the parton level without cuts and at the particle level with cuts. We find that the asymmetries are robust with respect to the higher-order QCD corrections and are indeed a very good probe of this anomalous coupling of the top. Hence, they can be used as experimental probes of the same.

We study the holographic dynamic anti-de Sitter/QCD description of a $\mathrm{SU}(N_c)$ non-Abelian gauge theory with $N_f$ fermions in the fundamental representation which also have Nambu–Jona-Lasinio (NJL) interactions included using Witten’s multitrace prescription. In particular, here, we study aspects of the dynamics in and near the conformal window of the gauge theory as described by the two-loop running of the gauge theory. If the number of flavors is such that the IR fixed point lies with the anomalous dimension, $\gamma$, of the quark bilinear above one, then chiral symmetry breaking occurs. Here, we display a spiral in the quark mass/condensate plane describing a sequence of unstable excited states of the vacuum. An attractive NJL operator enhances the vacuum condensate, but only an infinitely repulsive NJL interaction switches off the condensation completely. When $N_f$ changes so that the IR fixed point falls below 1 (the conformal window region), there is a numerical discontinuity in the phase structure with condensation only occurring with a supercritical NJL interaction. In the conformal window, the running of $\gamma$ to a nontrivial IR fixed point is similar to walking dynamics, although chiral symmetry breaking is not triggered. In the “ideal walking” scenario, chiral symmetry is broken in that IR conformal regime by the NJL interaction, but the change in $\gamma$ enhances the UV condensate. That enhancement of the condensate is shown in an analytic model with a sharp change in $\gamma$, and we show equivalent numerical results for the case of the two-loop running. In the model, the $\sigma$ becomes massless as the gauge theory running becomes near conformal, and we show it is possible to realize a light Higgs-like state in ideal walking models.

In this paper we perform a canonical analysis of the Schrödinger field and nonrelativistic electrodynamics coupled to Newton-Cartan gravity. We identify physical degrees of freedom and analyze the constraint structure of these theories.

The Sachdev-Ye-Kitaev (SYK) model can be used to describe black holes (BHs) in two-dimensional nearly anti–de Sitter gravity. We show that when such BHs are perturbed by a time-dependent negative-energy perturbation, their interior can be partially revealed. In the SYK model, a partial measurement of the state of the Majorana fermion pairs allows one to construct a matching time-dependent negative-energy perturbation of the BH geometry that shifts the state of the BH away from its equilibrium state. Kourkoulou and Maldacena showed that, if the perturbation is strong enough, the interior can be fully exposed and the BH disappears. Here, we show that when the perturbation is weaker than the threshold for full exposure, it effectively moves the horizon of the BH inwards, thus partially exposing the interior of the BH and leaving behind a smaller BH. The exposure is in proportion to the number of measured Majorana pairs and so also in proportion to the magnitude of the energy of the perturbation. From the boundary, the partial measurement is perceived as a burst of radiation whose strength and duration are proportional to the number of measured Majorana pairs.