It was pointed out long ago by Vainshtein [Phys. Lett. 39B, 393 (1972)] that the weak-field perturbation expansion of generic theories (of the nonlinear Fierz-Pauli type) involving massive spin-2 excitations breaks down below a certain distance around a material source (“Vainshtein radius”), scaling as some inverse power of the spin-2 mass $m_2$, i.e., some positive power of the range $m_2^{-1}$. Here we prove that this conclusion does not apply in a generalized Einstein-Cartan theory (called “torsion bigravity”) whose spectrum is made (like that of bimetric gravity) of a massless spin-2 excitation and a massive spin-2 one. Working within a static spherically symmetric ansatz, we prove, by reformulating the field equations in terms of new variables, that one can construct an all-order weak-field perturbative expansion where no denominators involving $m_2$ ever appear in the region $r\ll m_2^{-1}$. In particular, we show how the formal large-range limit, $m_2\to 0$, leads to a well-defined, finite perturbation expansion, whose all-order structure is discussed in some detail.

The Klein-Gordon equation is solved in the curved background spacetime created by a dispersive gravitational wave. Unlike solutions of perturbed Einstein equations in vacuum, dispersive gravitational waves do not travel exactly at the speed of light. As a consequence, the gravitational wave can resonantly exchange energy with scalar massive particles. Some details of the resonant interaction are displayed in a calculation demonstrating how relativistic particles (modeled by the Klein-Gordon equation), feeding on such gravitational waves, may be driven to extreme energies.

Nucleon spin structure functions have been investigated mainly by longitudinally polarized ones for finding the origin of the nucleon spin. Other types of spin structure functions are transversely polarized ones. In particular, quark transversity distributions in the nucleons have very different properties from the longitudinally polarized quark distribution functions, especially in scaling violation, because they are decoupled from the gluon transversity, due to the fact that they are helicity-flip (chiral-odd) distributions. Such studies are valuable for finding not only the origin of the nucleon spin but also a signature on physics beyond the standard model, because the electric dipole moment of the neutron is proportional to the transversity distributions. Now, there is experimental progress on the quark transversity distributions; however, there is no experimental information on gluon transversity. In fact, the gluon transversity does not exist for the spin-$1/2$ nucleon due to the helicity-conservation constraint. One needs a hadron with spin more than or equal to one, so that the helicity flip of two units is allowed. A stable spin-1 target is, for example, the deuteron for studying the gluon transversity. In this work, we propose a possibility for finding the gluon transversity at hadron-accelerator facilities, especially in the proton-deuteron Drell-Yan process with the linearly polarized deuteron, by showing theoretical formalism and numerical results. In the experiment, the information on the angular distribution of the dimuon is necessary in the final state; however, the proton beam does not have to be polarized. We show the dependencies of the Drell-Yan cross section on the dimuon-mass squared $M_{\mu \mu }^2$, the dimuon transverse-momentum $q_T$, the dimuon rapidity $y$ in the center-of-momentum frame, and the magnitude of the gluon transversity ${\mathrm{\Delta }}_{T}g$. We also show typical spin asymmetries in the Drell-Yan process. Since the internal spin-$1/2$ nucleons within the deuteron cannot contribute directly to the gluon transversity, it could be a good observable to find a new non-nucleonic component beyond the simple bound system of nucleons in nuclei.

We analyze the mixing between ${\mathrm{\Sigma }}^0$ and ${\mathrm{\Lambda }}^0$ based on the baryon masses. We distinguish the contributions from QCD and QED in the baryon mass splittings. We find that the mixing angle between ${\mathrm{\Sigma }}^0$ and ${\mathrm{\Lambda }}^0$ is $(2.07\pm 0.03)\times {10}^{-2}$, which leads to the decay branching fraction and up-down asymmetry of ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{e}^{+}{\nu }_e$ to be $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{e}^{+}{\nu }_e)=(1.5\pm 0.2)\times {10}^{-5}$ and $\alpha ({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{e}^{+}{\nu }_e)=-0.86\pm 0.04$, respectively. Moreover, we obtain that $\mathrm{\Delta }\mathcal{B}\equiv \mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{\pi }^{+})-\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^0)=(3.8\pm 0.5)\times {10}^{-4}$ and $\mathrm{\Delta }\alpha \equiv \alpha ({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^0{\pi }^{+})-\alpha ({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^0)=(-1.6\pm 0.7)\times {10}^{-2}$, which should vanish without the mixing.

Particle production sensitive to nonfactorizable and nonperturbative processes that contribute to the underlying event associated with a high transverse momentum ($p_T$) jet in $\mathrm{proton}+\mathrm{proton}$ collisions at $\sqrt{s}=200\mathrm{GeV}$ is studied with the STAR detector. Each event is divided into three regions based on the azimuthal angle with respect to the highest-$p_T$ jet direction: in the leading jet direction (“Toward”), opposite to the leading jet (“Away”), and perpendicular to the leading jet (“Transverse”). In the Transverse region, the average charged particle density is found to be between 0.4 and 0.6 and the mean transverse momentum, $⟨p_T⟩$, between 0.5 and $0.7\mathrm{GeV}/c$ for particles with $p_T>0.2\mathrm{GeV}/c$ at mid-pseudorapidity ($|\eta |<1$) and jet $p_T>15\mathrm{GeV}/c$. Both average particle density and $⟨p_T⟩$ depend weakly on the leading jet $p_T$. Closer inspection of the Transverse region hints that contributions to the underlying event from initial- and final-state radiation are significantly smaller in these collisions than at the higher energies, up to 13 TeV, recorded at the LHC. Underlying event measurements associated with a high-$p_T$ jet will contribute to our understanding of QCD processes at hard and soft scales at RHIC energies, as well as provide constraints to modeling of underlying event dynamics.

Recently in Phys. Rev. D 99, 104010 (2019), the nonrelativistic Feynman propagator for a harmonic oscillator system was presented when the generalized uncertainty principle is employed. In this short Comment we show that the expression is incorrect, and we derive its correct form.

We construct the gravitational theory emerging from the double-copy of massive scalar quantum chromodynamics in general dimensions. The resulting two-form-dilaton-gravity theory couples to flavored massive scalars gravitationally and via the dilaton. It displays scalar self-interaction terms of arbitrary even order in the fields but quadratic in derivatives. We work out the emerging Lagrangian explicitly up to the sixth order in scalar fields and propose an all order form.

We outline a general strategy developed for the analysis of critical models, which we apply to obtain a heuristic classification of all universality classes with up to three field-theoretical scalar order parameters in $d=6-\epsilon$ dimensions. As expected by the paradigm of universality, each class is uniquely characterized by its symmetry group and by a set of its scaling properties, neither of which are built-in by the formalism but instead emerge nontrivially as outputs of our computations. For three fields, we find several solutions mostly with discrete symmetries. These are nontrivial conformal field theory candidates in less than six dimensions, one of which is a new perturbatively unitary critical model.

We investigate the initial conditions of inflation in a Bianchi I universe that is homogeneous but not isotropic. We use the Eisenhart lift to describe such a theory geometrically as geodesics on a field-space manifold. We construct the phase-space manifold of the theory by considering the tangent bundle of the field space and equipping it with a natural metric. We find that the total volume of this manifold is finite for a wide class of inflationary models. We therefore take the initial conditions to be uniformly distributed over it in accordance with Laplace’s principle of indifference. This results in a normalizable, reparametrization invariant measure on the set of initial conditions of inflation in a Bianchi I universe. We find that this measure favors an initial state in which the inflaton field is at or near its minimum, with a mild preference for some initial anisotropy. Since inflation requires an initial field value with a large displacement from its minimum, we therefore conclude that the theory of inflation requires finely tuned initial conditions.

We provide a general framework for studying the dark energy cosmology in which a scalar field $\varphi$ is nonminimally and kinetically coupled to cold dark matter (CDM). The scalar-graviton sector is described by the action of Horndeski theories with the speed of gravitational waves equivalent to that of light, whereas CDM is treated as a perfect fluid given by a Schutz-Sorkin action. We consider two interacting Lagrangians of the forms $f_1(\varphi ,X){\rho }_c(n_c)$ and $f_2(n_c,\varphi ,X)J_c^{\mu }{\partial }_{\mu }\varphi$, where $X=-{\partial }^{\mu }\varphi {\partial }_{\mu }\varphi /2$, ${\rho }_c$ and $n_c$ are the energy density and number density of CDM respectively, and $J_c^{\mu }$ is a vector field related to the CDM four velocity. We derive the scalar perturbation equations of motion without choosing any special gauges and identify conditions for the absence of ghosts and Laplacian instabilities on scales deep inside the sound horizon. Applying a quasistatic approximation in a gauge-invariant manner, we also obtain the effective gravitational couplings felt by CDM and baryons for the modes relevant to the linear growth of large-scale structures. In particular, the $n_c$ dependence in the coupling $f_2$ gives rise to an interesting possibility for realizing the gravitational coupling with CDM weaker than the Newton gravitational constant $G$.

We explore the effects of incorporating redshift uncertainty into measurements of galaxy clustering and cross-correlations of galaxy positions and cosmic microwave background (CMB) lensing maps. We use a simple Gaussian model for a redshift distribution in a redshift bin with two parameters: the mean, $z_0$, and the width, ${\sigma }_{\mathrm{z}}$. We vary these parameters, as well as a galaxy bias parameter, $b_{\mathrm{g}}$, and a matter fluctuations parameter, ${\sigma }_8$, for each redshift bin, as well as the parameter ${\mathrm{\Omega }}_{\mathrm{m}}$, in a Fisher analysis across 12 redshift bins from $z=0–7$. We find that incorporating redshift uncertainties degrades constraints on ${\sigma }_8(z)$ in the Large Synoptic Survey Telescope (LSST)/CMB-S4 era by about a factor of 10 compared to the case of perfect redshift knowledge. In our fiducial analysis of LSST/CMB-S4 including redshift uncertainties, we project constraints on ${\sigma }_8(z)$ for $z<3$ of less than 5%. Galaxy imaging surveys are expected to have priors on redshift parameters from photometric redshift algorithms and other methods. When adding priors with the expected precision for LSST redshift algorithms, the constraints on ${\sigma }_8(z)$ can be improved by a factor of 2–3 compared to the case of no prior information. We also find that “self-calibrated” constraints on the redshift parameters from just the autocorrelation and cross-correlation measurements (with no prior information) are competitive with photometric redshift techniques. In the LSST/CMB-S4 era, we find uncertainty on the redshift parameters ($z_0,{\sigma }_{\mathrm{z}}$) to be below $0.004(1+\mathrm{z})$ at $z<1$. For all parameters, constraints improve significantly if smaller scales can be used. We also project constraints for nearer term survey combinations, Dark Energy Survey (DES)/SPT-SZ, DES/SPT-3G, and LSST/SPT-3G, and analyze how our constraints depend on a variety of parameter and model choices.

We use a semianalytic approach that is calibrated to N-body simulations to study the evolution of self-interacting dark matter cores in galaxies. We demarcate the regime where the temporal evolution of the core density follows a well-defined track set by the initial halo parameters and the cross section. Along this track, the central density reaches a minimum value set by the initial halo density. Further evolution leads to an outward heat transfer, inducing gravothermal core collapse such that the core shrinks as its density increases. We show that the timescale for the core collapse is highly sensitive to the outer radial density profile. Satellite galaxies with significant mass loss due to tidal stripping should have larger central densities and significantly faster core collapse compared to isolated halos. Such a scenario could explain the dense and compact cores of dwarf galaxies in the Local Group like Tucana (isolated from the Milky Way), the classical Milky Way satellite Draco, and some of the ultrafaint satellites. If the ultimate fate of core collapse is black hole formation, then the accelerated timescale provides a new mechanism for creating intermediate-mass black holes.

Recently, the Belle Collaboration reported a new exotic state $Y(4620)$ with mass at 4625.9 MeV in the positronium annihilation process. Inspired by experiment, we study the tetraquark system $c\overline{s}s\overline{c}$ with quantum numbers $J^P=1^{-}$ in the framework of chiral constituent quark model with the help of Gaussian expansion method. Two structures, diquark-antidiquark and meson-meson, with all possible color and spin configurations are considered. The result shows that no bound state can be formed. To investigate the possible resonance states, the real scaling method is employed. Several resonance states with energies 4354, 4408, 4469, 4497, and 4531 MeV are proposed. Taking into account the errors in calculating the $q\overline{q}$ mesons, the system errors in the calculation of four-quark system are around 60–100 MeV. The resonance with energy 4531 MeV is possible the candidate of the newly found state $Y(4620)$.

The magnetic and quadrupole moments of the vector and axial-vector mesons containing a heavy quark are estimated within the light-cone sum rules method. Our predictions on magnetic moments for the vector mesons are compared with the results obtained by other approaches.

We present a dispersive analysis of the double-virtual photon-photon scattering to two pions up to 1.5 GeV. Through unitarity, this process is very sensitive to hadronic final-state interaction. For the $s$-wave, we use a coupled-channel $\pi \pi$, $K\overline{K}$ analysis which allows for a simultaneous description of both $f_0(500)$ and $f_0(980)$ resonances. For higher energies, $f_2(1270)$ shows up as a dominant structure which we approximate by a single-channel $\pi \pi$ rescattering in the $d$-wave. In the dispersive approach, the latter requires taking into account $t$- and $u$-channel vector-meson exchange left-hand cuts which exhibit an anomalouslike behavior for large spacelike virtualities. We show how to readily incorporate such behavior using a contour deformation. Besides, we devote special attention to kinematic constraints of helicity amplitudes and show their correlations explicitly.

We study the operator product expansion (OPE) of two identical scalar primary operators in the light-cone limit in a conformal field theory (CFT) where a scalar is the operator with lowest twist. We see that in CFTs where both the stress tensor and a scalar are the lowest twist operators, the stress tensor contributes at the leading order in the light-cone OPE and the scalar contributes at the subleading order. We also see that there does not exist a scalar analog of the average null energy condition for a CFT where a scalar is the lowest twist operator.

We study the effect of superfluidity on the tidal response of a neutron star in a general relativistic framework. In this work, we take a dual-layer approach where the superfluid matter is confined in the core of the star. Then the superfluid core is encapsulated with an envelope of ordinary matter fluid which acts effectively as the low density crustal region of the star. In the core, the matter content is described by a two-fluid model where only the neutrons are taken as superfluid and the other fluid consists of protons and electrons making it charge neutral. We calculate the values of various tidal love numbers of a neutron star and discuss how they are affected due to the presence of entrainment between the two fluids in the core. We also emphasize that more than one tidal parameter is necessary to probe superfluidity with the gravitational wave from the binary inspiral.

The cosmic censorship conjecture essentially states that naked singularities should not form from generic initial conditions. Since black hole parameters can change their values under Hawking evaporation, one has to ask whether it is possible to reach extremality by simply waiting for the black hole to evaporate. If so a slight perturbation would likely render the singularity naked. Fortunately, at least for the case of an asymptotically flat 4-dimensional Reissner-Nordström black hole, Hiscock and Weems showed that it can never reach extremality despite the fact that for a sufficiently massive black hole, its charge-to-mass ratio can increase during Hawking evaporation. Hence, cosmic censorship is never violated by Hawking emission. However, we know that under some processes, it is easier to violate cosmic censorship in higher dimensions; therefore, it is crucial to generalize the Hiscock and Weems model to dimensions above four to check cosmic censorship. We found that Hawking evaporation cannot lead to violation of cosmic censorship even in higher dimensional Reissner-Nordström spacetimes. Moreover, it seems to be more difficult to reach extremality as the number of dimensions increases.

The observed light curves and other properties of the two extragalactic fast x-ray transients, CDF-S XT1 and CDF-S XT2, which were discovered recently in archival data of the Chandra Deep Field-South (CDF-S) observations, indicate that they belong to two different populations of x-ray transients. XT1 seems to be an x-ray flash, i.e., a narrowly beamed long duration gamma ray burst viewed from far off axis, while XT2 seems to be a nebular emission powered by a newly born millisecond pulsar in a binary neutron stars merger.

We report on an improved measurement of the ${}^8\mathrm{B}$ solar neutrino interaction rate with the Borexino experiment at the Laboratori Nazionali del Gran Sasso. Neutrinos are detected via their elastic scattering on electrons in a large volume of liquid scintillator. The measured rate of scattered electrons above 3 MeV of energy is ${0.223}_{-0.016}^{+0.015}(\mathrm{stat}){}_{-0.006}^{+0.006}(\mathrm{syst})\mathrm{cpd}/100\mathrm{t}$, which corresponds to an observed solar neutrino flux assuming no neutrino flavor conversion of ${\mathrm{\Phi }}_{{}^8\mathrm{B}}^{\mathrm{ES}}=2.57_{-0.18}^{+0.17}(\mathrm{stat}){}_{-0.07}^{+0.07}(\mathrm{syst})\times {10}^6{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$. This measurement exploits the active volume of the detector in almost its entirety for the first time, and takes advantage of a reduced radioactive background following the 2011 scintillator purification campaign and of novel analysis tools providing a more precise modeling of the background. Additionally, we set a new limit on the interaction rate of solar hep neutrinos, searched via their elastic scattering on electrons as well as their neutral current-mediated inelastic scattering on carbon, ${}^{12}\mathrm{C}(\nu ,{\nu }^{\prime }){}^{12}{\mathrm{C}}^{*}$ ($E_{\gamma }=15.1\mathrm{MeV}$).