We demonstrate that the tentative detection of a few antihelium events with the Alpha Magnetic Spectrometer (AMS) on board the International Space Station can, in principle, be ascribed to the annihilation or decay of Galactic dark matter, when accounting for uncertainties in the coalescence process leading to the formation of antinuclei. We show that the predicted antiproton rate, assuming the antihelium events came from dark matter, is marginally consistent with AMS data, as is the antideuteron rate with current available constraints. We argue that a dark matter origin can be tested with better constraints on the coalescence process, better control of misidentified events, and with future antideuteron data.

The long-standing discrepancy between the experimental determination by the Muon $g-2$ Collaboration at Brookhaven and the Standard Model predictions for the anomalous magnetic moment of the muon cannot be explained within a simple unified framework like the constrained minimal supersymmetric standard model, but it can within its extension with vectorlike fermions. In this paper we consider a model with an additional vectorlike $5+\overline{5}$ pair of $SU(5)$. Within this model we first identify its parameter space that is consistent with the current discrepancy and show that this implies the lighter chargino mass in the range of 700–1200 GeV. We examine how it is affected by constraints from the electroweak sparticle search at the LHC based on a 13 TeV search with $36.1{\mathrm{fb}}^{-1}$ integrated luminosity. We show that null trilepton signal searches coming from chargino-neutralino pair production significantly constrain the allowed parameter space except when the chargino-neutralino mass difference is relatively small, below about 10 GeV. Next we consider the expected impact of the New Muon $g-2$ experiment at Fermilab with its projected sensitivity reach of $7\sigma$ and, assuming it confirms the current discrepancy, show that the remaining parameter space of the considered model will be in strong tension with the current LHC limits.

Drastic changes in the early Universe such as first-order phase transition can produce a stochastic gravitational wave (GW) background. We investigate the testability of a scale invariant extension of the standard model (SM) using the GW background produced by the chiral phase transition in a strongly interacting QCD-like hidden sector, which, via a SM singlet real scalar mediator, triggers the electroweak phase transition. Using the Nambu–Jona-Lasinio method in a mean field approximation we estimate the GW signal and find that it can be tested by future space-based detectors.

Recently, the LHCb Collaboration has reported the excesses in the $b\to sll$ processes. One of the promising candidates for new physics to explain the anomalies is the extended Standard Model (SM) with vectorlike quarks and leptons. In that model, Yukawa couplings between the extra fermions and SM fermions are introduced, adding extra scalars. Then, the box diagrams involving the extra fields achieve the $b\to sll$ anomalies. It has been known that the excesses require the large Yukawa couplings of leptons, so that this kind of model can be tested by studying correlations with other observables. In this paper, we consider the extra scalar to be a dark matter (DM) candidate, and investigate DM physics as well as the flavor physics and the LHC physics. The DM relic density and the direct-detection cross section are also dominantly given by the Yukawa couplings, so that we find some explicit correlations between DM physics and the flavor physics. In particular, we find the predictions of the $b\to sll$ anomalies against the direct detection of DM.

The next-to-leading order (NLO) corrections to the deep inelastic scattering structure functions $F_2$ and $F_L$ (or equivalently the photon-target cross sections ${\sigma }_T^{{\gamma }^{*}}$ and ${\sigma }_L^{{\gamma }^{*}}$) at low $x_{Bj}$ are obtained, as a generalization of the dipole factorization formula. For the first time, the contributions of both the $q\overline{q}$ and the $q\overline{q}g$ Fock states in the photon are directly calculated, using earlier results [G. Beuf, Phys. Rev. D 94, 054016 (2016)] for the $q\overline{q}$ light-front wave functions at one loop inside a dressed virtual photon. Both the $q\overline{q}$ and $q\overline{q}g$ contributions have UV divergences, which are shown to cancel each other, using conventional dimensional regularization as UV regulator. Finally, the resummation of high-energy logarithms on top of the NLO results for ${\sigma }_T^{{\gamma }^{*}}$ and ${\sigma }_L^{{\gamma }^{*}}$ is discussed.

We highlight how the existence of an ultraviolet completion for interacting standard-model type matter puts constraints on the viable microscopic dynamics of asymptotically safe quantum gravity within truncated Renormalization Group flows. A first constraint—the weak-gravity bound—is rooted in the destruction of quantum scale-invariance in the matter system by strong quantum-gravity fluctuations. A second constraint arises by linking Planck-scale dynamics to the dynamics at the electroweak scale. Specifically, we delineate how to extract a prediction of the top quark mass from asymptotically safe gravity and stress that a finite top mass could be difficult to accommodate in a significant part of the gravitational coupling space.

We compute scattering amplitudes of the regularized bosonic Nambu-Goto string in the mean-field approximation, disregarding fluctuations of the Lagrange multiplier and an independent metric about their mean values. We use the previously introduced Lilliputian scaling limit to recover the Regge behavior of the amplitudes with the usual linear Regge trajectory in space-time dimensions $d>2$. We demonstrate a stability of this minimum of the effective action under fluctuations for $d<26$.

We show that local Lorentz covariance arises canonically as the group of transformations between local thermal states in the framework of local quantum physics, given the following three postulates: (i) Local observable algebras are finite-dimensional. (ii) Minimal local observable algebras are isomorphic to ${\mathbb{M}}_2(\mathbb{C})$, the observable algebra of a single qubit. (iii) The vacuum restricted to any minimal local observable algebra is a nonmaximally mixed thermal state. The derivation reveals a new and surprising relation between spacetime structure and local quantum states. In particular, we show how local restrictions of the vacuum can determine the connection between different local inertial reference frames.

We analyze correlations between pairs of particle detectors quadratically coupled to a real scalar field. We find that, while a single quadratically coupled detector presents no divergences, when one considers pairs of detectors, there emerge unanticipated persistent divergences (not regularizable via smooth switching or smearing) in the entanglement they acquire from the field. We have characterized such divergences, discussed whether a suitable regularization can allow for fair comparison of the entanglement harvesting ability of the quadratic and the linear couplings, and finally found a UV-safe quantifier of harvested correlations. Our results are relevant to future studies of the entanglement structure of the fermionic vacuum.

Symmetries are essential for a consistent formulation of many quantum systems. In this paper we discuss a fundamental symmetry, which is present for any Lagrangian term that involves ${\dot{x}}^2$. As a basic model that incorporates the fundamental symmetries of quantum gravity and string theory, we consider the Lagrangian action of the relativistic point particle. A path integral quantization for this seemingly simple system has long presented notorious problems. Here we show that those problems are overcome by taking into account the additional symmetry, leading directly to the exact Klein-Gordon propagator.

We develop a formalism to extend our previous work on the electromagnetic $\delta$-function plates to a spherical surface. The electric (${\lambda }_e$) and magnetic (${\lambda }_g$) couplings to the surface are through $\delta$-function potentials defining the dielectric permittivity and the diamagnetic permeability, with two anisotropic coupling tensors. The formalism incorporates dispersion. The electromagnetic Green’s dyadic breaks up into transverse electric and transverse magnetic parts. We derive the Casimir interaction energy between two concentric $\delta$-function spheres in this formalism and show that it has the correct asymptotic flat-plate limit. We systematically derive expressions for the Casimir self-energy and the total stress on a spherical shell using a $\delta$-function potential, properly regulated by temporal and spatial point splitting, which are different from the conventional temporal point splitting. In the strong-coupling limit, we recover the usual result for the perfectly conducting spherical shell but in addition there is an integrated curvature-squared divergent contribution. For finite coupling, there are additional divergent contributions; in particular, there is a familiar logarithmic divergence occurring in the third order of the uniform asymptotic expansion that renders it impossible to extract a unique finite energy except in the case of an isorefractive sphere, which translates into ${\lambda }_g=-{\lambda }_e$.

In this work we consider the spontaneous symmetry breaking of the electroweak $SU(2{)}_L\times U(1{)}_Y$ gauge group into $U(1{)}_{em}$ taking place in the Standard Model of particle physics as seen from the point of view of an accelerating observer. According to the Unruh effect, that observer detects the Minkowski vacuum as a thermal bath at a temperature proportional to the proper acceleration $a$. Then we show that (in a certain large $N$ limit) when the acceleration is bigger than the critical value $a_c=4\pi v$ (where $v$ is the Higgs vacuum expectation value), the electroweak $SU(2{)}_L\times U(1{)}_Y$ gauge symmetry is restored and all elementary particles become massless. In addition, even observers with $a<a_c$ can see this symmetry restoration in the region close to the Rindler horizon.

We discuss optimal strategy for follow-up observations by 1–3 m class optical/infrared telescopes which target optical/infrared counterparts of gravitational wave events detected with two laser interferometric gravitational wave detectors. The probability maps of transient sources, such as coalescing neutron stars and/or black holes, determined by two laser interferometers generally spread widely. They include the distant region where it is difficult for small aperture telescopes to observe the optical/infrared counterparts. For small telescopes, there is a possibility that it is more advantageous to search for nearby region even if the probability inferred by two gravitational wave detectors is low. We show that in the case of the first three events of advanced LIGO, the posterior probability map, derived by using a distance prior restricted to a nearby region, is different from that derived without such restriction. This suggests that the optimal strategy for small telescopes to perform follow-up observation of LIGO-Virgo’s three events are different from what has been searched so far. We also show that, when the binary is nearly edge-on, it is possible that the true direction is not included in the 90% posterior probability region. We discuss the optimal strategy to perform optical/infrared follow-up observation with small aperture telescopes based on these facts.

Axisymmetric rotating radially excited boson stars are analyzed. For several fixed parameter sets, the full sets of solutions are obtained. In contrast to the nodeless boson stars, the radially excited sets of solutions do not exhibit a spiraling behavior. Instead, they form a loop when the boson frequency is varied from its maximal value given by the boson mass to a minimal value and back. Thus, for all allowed boundary data of the scalar field at the origin, there are two distinct solutions, except for the end points. While one end point corresponds to the trivial solution, the other one represents the most compact solution. The energy density and the pressures of the solutions are analyzed. A decomposition of the scalar field into spherical harmonics is performed, and stability considerations are presented.

We compute the leading post-Newtonian (PN) contributions at quadratic order in the spins to the radiation-reaction acceleration and spin evolution for binary systems, entering at four-and-a-half PN order. Our calculation includes the backreaction from finite-size spin effects, which is presented for the first time. The computation is carried out, from first principles, using the effective field theory framework for spinning extended objects. At this order, nonconservative effects in the spin-spin sector are independent of the spin supplementary conditions. A nontrivial consistency check is performed by showing that the energy loss induced by the resulting radiation-reaction force is equivalent to the total emitted power in the far zone. We find that, in contrast to the spin-orbit contributions (reported in a companion paper), the radiation reaction affects the evolution of the spin vectors once spin-spin effects are incorporated.

We compute the leading post-Newtonian (PN) contributions at linear order in the spin to the radiation-reaction acceleration and spin evolution for binary systems, which enter at fourth PN order. The calculation is carried out, from first principles, using the effective field theory framework for spinning compact objects, in both the Newton-Wigner and covariant spin supplementary conditions. A nontrivial consistency check is performed on our results by showing that the energy loss induced by the resulting radiation-reaction force is equivalent to the total emitted power in the far zone, up to so-called “Schott terms.” We also find that, at this order, the radiation reaction has no net effect on the evolution of the spins. The spin-spin contributions to radiation reaction are reported in a companion paper.

Inspiraling and merging binary neutron stars are not only important source of gravitational waves, but also promising candidates for coincident electromagnetic counterparts. These systems are thought to be progenitors of short gamma-ray bursts (sGRBs). We have shown previously that binary neutron star mergers that undergo delayed collapse to a black hole surrounded by a weighty magnetized accretion disk can drive magnetically powered jets. We now perform magnetohydrodynamic simulations in full general relativity of binary neutron stars mergers that undergo prompt collapse to explore the possibility of jet formation from black hole- light accretion disk remnants. We find that after $t-t_{\mathrm{BH}}\sim 26(M_{\mathrm{NS}}/1.8M_{\odot })\mathrm{ms}$ ($M_{\mathrm{NS}}$ is the ADM mass) following prompt black hole formation, there is no evidence of mass outflow or magnetic field collimation. The rapid formation of the black hole following merger prevents magnetic energy from approaching force-free values above the magnetic poles, which is required for the launching of a jet by the usual Blandford-Znajek mechanism. Detection of gravitational waves in coincidence with sGRBs may provide constraints on the nuclear equation of state (EOS): the fate of an NSNS merger–delayed or prompt collapse, and hence the appearance or nonappearance of an sGRB–depends on a critical value of the total mass of the binary, and this value is sensitive to the EOS.

In standard general relativity the universe cannot be started with arbitrary initial conditions, because four of the ten components of the Einstein’s field equations (EFE) are constraints on initial conditions. In the previous work it was proposed to extend the gravity theory to allow free initial conditions, with a motivation to solve the cosmological constant problem. This was done by setting four constraints on metric variations in the action principle, which is reasonable because the gravity’s physical degrees of freedom are at most six. However, there are two problems about this theory; the three constraints in addition to the unimodular condition were introduced without clear physical meanings, and the flat Minkowski spacetime is unstable against perturbations. Here a new set of gravitational field equations is derived by replacing the three constraints with new ones requiring that geodesic paths remain geodesic against metric variations. The instability problem is then naturally solved. Implications for the cosmological constant $\mathrm{\Lambda }$ are unchanged; the theory converges into EFE with nonzero $\mathrm{\Lambda }$ by inflation, but $\mathrm{\Lambda }$ varies on scales much larger than the present Hubble horizon. Then galaxies are formed only in small $\mathrm{\Lambda }$ regions, and the cosmological constant problem is solved by the anthropic argument. Because of the increased degrees of freedom in metric dynamics, the theory predicts new non-oscillatory modes of metric anisotropy generated by quantum fluctuation during inflation, and CMB $B$-mode polarization would be observed differently from the standard predictions by general relativity.