A ${\mathrm{\Sigma }}^{*}$ state with spin parity $J^P=1/2^{-}$ with mass and width around 1380 and 120 MeV, referred to as the ${\mathrm{\Sigma }}_{1/2^{-}}^{*}(1380)$, has been predicted in several pentaquark models and inferred from the analysis of CLAS $\gamma p$ data. In the present work, we discuss how one can employ the ${\mathrm{\Lambda }}_c^{+}\to \eta {\pi }^{+}\mathrm{\Lambda }$ decay to test its existence, as well as to study the ${\mathrm{\Sigma }}^{*}(1385)$ state with $J^P=3/2^{+}$. Because the final ${\pi }^{+}\mathrm{\Lambda }$ system is in a pure isospin $I=1$ combination, the ${\mathrm{\Lambda }}_c^{+}\to \eta {\pi }^{+}\mathrm{\Lambda }$ decay can be an ideal process to study these ${\mathrm{\Sigma }}^{*}$ resonances. In particular, we show that the decay angle and energy distributions of the ${\pi }^{+}$ are very different for ${\mathrm{\Sigma }}^{*}(1385)$ and ${\mathrm{\Sigma }}_{1/2^{-}}^{*}(1380)$. The proposed decay mechanism as well as the existence of the ${\mathrm{\Sigma }}_{1/2^{-}}^{*}(1380)$ state can be checked by future BESIII and Belle experiments.

Determination of trilinear Higgs coupling (${\lambda }_{HHH}=\kappa {\lambda }_{HHH}^{\mathrm{SM}}$) through Higgs pair productions is a major motivation for the LHC high-luminosity phase. We perform a detailed collider simulation to explore the potential of measuring ${\lambda }_{HHH}$ in the $VHH$ ($V=W$, $Z$) production at the high-luminosity Large Hadron Collider. We find that the trilinear Higgs coupling in the standard model (${\lambda }_{HHH}^{\mathrm{SM}}$) can be measured at the level of $1.3\sigma$. Combining with the gluon fusion, vector boson fusion, and $t\overline{t}HH$ channels, ${\lambda }_{HHH}^{\mathrm{SM}}$ is expected to be measured at the level of $3.13\sigma$. If no evidence of Higgs pair productions is observed, the $VHH$ production, together with the gluon fusion channel, imposes a bound of $0.5\le \kappa \le 2.2$ at the 95% confidence level.

In this paper we calculate the next-to-leading order (NLO) QCD $[\mathcal{O}({\alpha }_s{\alpha }^3)]$ and electroweak (EW) $[\mathcal{O}({\alpha }^4)]$ corrections to the $WWW$ production at the LHC and deal with the subsequent leptonic decays from $W$ bosons by adopting an improved narrow-width approximation which takes into account the spin correlation and finite-width effects. The NLO QCD correction from the real jet radiation is discussed, which significantly enhances the production rate, particularly in the high-energy region. We also provide the integrated cross section for the $WWW$ production and various kinematic distributions of final products at the $\mathrm{QCD}+\mathrm{EW}$ NLO. We find that the convergence of the perturbative QCD description can be improved by applying a hard jet veto in the event selection, but this jet veto would introduce a new source of theoretical uncertainty. The pure NLO QCD relative correction to the integrated cross section for the $W^{+}{W}^{-}{W}^{+}$ production at the 14 TeV LHC is on the order of 30% in the jet-veto event selection scheme with $p_{T,\text{jet}}^{\mathrm{cut}}=50\mathrm{GeV}$, while the genuine NLO EW relative correction can reach about 15% in the inclusive event selection scheme. Our numerical results show that both the NLO QCD and NLO EW corrections should be taken into consideration in precision predictions.

In this paper, we construct and study solutions of Einstein’s equations in a vacuum with a positive cosmological constant which can be considered as inhomogeneous generalizations of the Nariai cosmological model. Similar to this Nariai spacetime, our solutions are at the borderline between gravitational collapse and de Sitter-like exponential expansion. Our studies focus in particular on the intriguing oscillatory dynamics which we discover. Our investigations are carried out both analytically (using heuristic mode analysis arguments) and numerically (using the numerical infrastructure recently introduced by us).

We demonstrate that Casimir forces associated with zero-point fluctuations of quantum vacuum may be substantially affected by the presence of dynamical topological defects. In order to illustrate this nonperturbative effect we study the Casimir interactions between dielectric wires in a compact formulation of Abelian gauge theory in two spatial dimensions. The model possesses topological defects, instantonlike monopoles, which are known to be responsible for nonperturbative generation of a mass gap and for a linear confinement of electrically charged probes. Despite the fact the model has no matter fields, the Casimir energy depends on the value of the gauge coupling constant. We show, both analytically and numerically, that in the strong coupling regime the Abelian monopoles make the Casimir forces short ranged. Simultaneously, their presence increases the interaction strength between the wires at short distances for a certain range of values of the gauge coupling. The wires suppress monopole density in the space between them compared to the density outside the wires. In the weak coupling regime the monopoles become dilute and the Casimir potential reduces to a known theoretical result that does not depend on the gauge coupling.

Working in relativistic quantum field theory, we derive the quantization condition satisfied by coupled two- and three-particle systems of identical scalar particles confined to a cubic spatial volume with periodicity $L$. This gives the relation between the finite-volume spectrum and the infinite-volume $\mathbf{2}\to \mathbf{2}$, $\mathbf{2}\to \mathbf{3}$, and $\mathbf{3}\to \mathbf{3}$ scattering amplitudes for such theories. The result holds for relativistic systems composed of scalar particles with nonzero mass $m$, whose center of mass energy lies below the four-particle threshold, and for which the two-particle $K$ matrix has no singularities below the three-particle threshold. The quantization condition is exact up to corrections of the order $\mathcal{O}(e^{-mL})$ and holds for any choice of total momenta satisfying the boundary conditions.

The $N$-jettiness observable ${\mathcal{T}}_N$ provides a way of describing the leading singular behavior of the $N$-jet cross section in the $\tau ={\mathcal{T}}_N/Q\to 0$ limit, where $Q$ is a hard interaction scale. We consider subleading-power corrections in the $\tau \ll 1$ expansion, and employ soft-collinear effective theory to obtain analytic results for the dominant ${\alpha }_s\tau \ln \tau$ and ${\alpha }_s^2\tau {\ln }^3\tau$ subleading terms for thrust in $e^{+}{e}^{-}$ collisions and 0-jettiness for $q\overline{q}$-initiated Drell-Yan–like processes at hadron colliders. These results can be used to significantly improve the numerical accuracy and stability of the $N$-jettiness subtraction technique for performing fixed-order calculations at next-to-leading order and next-to-next-to-leading order. They reduce the size of missing power corrections in the subtractions by an order of magnitude. We also point out that the precise definition of $N$-jettiness has an important impact on the size of the power corrections and thus the numerical accuracy of the subtractions. The sometimes employed definition of $N$-jettiness in the hadronic center-of-mass frame suffers from power corrections that grow exponentially with rapidity, causing the power expansion to deteriorate away from central rapidity. This degradation does not occur for the original $N$-jettiness definition, which explicitly accounts for the boost of the Born process relative to the frame of the hadronic collision, and has a well-behaved power expansion throughout the entire phase space. Integrated over rapidity, using this $N$-jettiness definition in the subtractions yields another order of magnitude improvement compared to employing the hadronic-frame definition.

Generalizing the results in Chruściel and Hörzinger [J. High Energy Phys. 16 (2016) 1], we construct further families of compact Einstein-Maxwell instantons associated with the Kerr–Newman metrics with a positive cosmological constant.

We study the Casimir-Polder force arising between two identical two-level atoms and mediated by a massless scalar field propagating in a black-hole background. We study the interplay of Hawking radiation and Casimir-Polder forces and find that, when the atoms are placed near the event horizon, the scaling of the Casimir-Polder interaction energy as a function of interatomic distance displays a transition from a thermal-like character to a nonthermal behavior. We corroborate our findings for a quantum field prepared in the Boulware, Hartle-Hawking, and Unruh vacua. Our analysis is consistent with the nonthermal character of the Casimir-Polder interaction of two-level atoms in a relativistic accelerated frame [J. Marino et al., Phys. Rev. Lett. 113, 020403 (2014)], where a crossover from thermal scaling, consistent with the Unruh effect, to a nonthermal scaling has been observed. The two crossovers are a consequence of the noninertial character of the background where the field mediating the Casimir interaction propagates. While in the former case the characteristic crossover length scale is proportional to the inverse of the surface gravity of the black hole, in the latter it is determined by the inverse of the proper acceleration of the atoms.

Color symmetry is spontaneously broken in quark matter at high density as a consequence of di-quark condensations with exhibiting color superconductivity. Non-Abelian vortices or color magnetic flux tubes stably exist in the color-flavor locked phase at asymptotically high density. The effective worldsheet theory of a single non-Abelian vortex was previously calculated in the singular gauge to obtain the $\mathbb{C}{P}^2$ model [1,2]. Here, we reconstruct the effective theory in a regular gauge without taking a singular gauge, confirming the previous results in the singular gauge. As a byproduct of our analysis, we find that non-Abelian vortices in high-density QCD do not suffer from any obstruction for the global definition of a symmetry breaking.

We consider an asymptotically free vectorial $\mathrm{SU}(N_c)$ gauge theory with $N_f$ massless fermions in a representation $R$, having an infrared fixed point (IRFP) of the renormalization group at ${\alpha }_{\mathrm{IR}}$ in the conformal non-Abelian Coulomb phase. The cases with $R$ equal to the fundamental, adjoint, and symmetric rank-2 tensor representation are considered. We present scheme-independent calculations of the anomalous dimension ${\gamma }_{\overline{\psi }\psi ,\mathrm{IR}}$ to $O({\mathrm{\Delta }}_f^4)$ and ${\beta }_{\mathrm{IR}}^{\prime }$ to $O({\mathrm{\Delta }}_f^5)$ at this IRFP, where ${\mathrm{\Delta }}_f$ is an $N_f$-dependent expansion parameter. Comparisons are made with conventional $n$-loop calculations and lattice measurements. As a test of the accuracy of the ${\mathrm{\Delta }}_f$ expansion, we calculate ${\gamma }_{\overline{\psi }\psi ,\mathrm{IR}}$ to $O({\mathrm{\Delta }}_f^3)$ in $\mathcal{N}=1$ $\mathrm{SU}(N_c)$ supersymmetric quantum chromodynamics and find complete agreement, to this order, with the exactly known expression. The ${\mathrm{\Delta }}_f$ expansion also avoids a problem in which an IRFP may not be manifest as an IR zero of a higher $n$-loop beta function.

The direct detection of gravitational waves (GWs) is an invaluable new tool to probe gravity and the nature of cosmic acceleration. A large class of scalar-tensor theories predicts that GWs propagate with velocity different than the speed of light, a difference that can be $\mathcal{O}(1)$ for many models of dark energy. We determine the conditions behind the anomalous GW speed, namely, that the scalar field spontaneously breaks Lorentz invariance and couples to the metric perturbations via the Weyl tensor. If these conditions are realized in nature, the delay between GW and electromagnetic signals from distant events will run beyond human time scales, making it impossible to measure the speed of GWs using neutron star mergers or other violent events. We present a robust strategy to exclude or confirm an anomalous speed of GWs using eclipsing binary systems, the electromagnetic phase of which can be exquisitely determined. The white dwarf binary $\mathrm{J}0651+2844$ is a known example of such a system that can be used to probe deviations in the GW speed as small as $c_g/c-1\gtrsim 2\times {10}^{-12}$ when LISA comes online. This test will either eliminate many contender models for cosmic acceleration or wreck a fundamental pillar of general relativity.

We derive the exact gravitational wave solutions in a general class of quadratic Poincaré gauge gravity models. The Lagrangian includes all possible linear and quadratic invariants constructed from the torsion and the curvature, including the parity odd terms. The Ansatz for the gravitational wave configuration and the properties of the wave solutions are patterned following the corresponding Ansatz and the properties of the plane-fronted electromagnetic wave.

We prove the nonexistence of massive scalar, vector and tensor hairs outside the surface of a static and stationary compact reflecting star. Our result is the extension of the no-hair theorem for black holes to horizonless compact configurations with reflecting boundary condition at the surface. We also generalize the proof for spacetimes with a positive cosmological constant.

We consider the scalar field profile around relativistic compact objects such as neutron stars for a range of modified gravity models with screening mechanisms of the chameleon and Damour-Polyakov types. We focus primarily on inverse power law chameleons and the environmentally dependent dilaton as examples of both mechanisms. We discuss the modified Tolman-Oppenheimer-Volkoff equation and then implement a relaxation algorithm to solve for the scalar profiles numerically. We find that chameleons and dilatons behave in a similar manner and that there is a large degeneracy between the modified gravity parameters and the neutron star equation of state. This is exemplified by the modifications to the mass-radius relationship for a variety of model parameters.

We investigate constraints on the abundance of primordial black holes (PBHs) in the mass range ${10}^{15}–{10}^{17}\mathrm{g}$ using data from the cosmic microwave background (CMB) and MeV extragalactic gamma-ray background (EGB). Hawking radiation from PBHs with lifetime greater than the age of the Universe leaves an imprint on the CMB through modification of the ionization history and the damping of CMB anisotropies. Using a model for redshift-dependent energy injection efficiencies, we show that a combination of temperature and polarization data from Planck provides the strongest constraint on the abundance of PBHs for masses $\sim {10}^{15}–{10}^{16}\mathrm{g}$, while the EGB dominates for masses $\gtrsim {10}^{16}\mathrm{g}$. Both the CMB and EGB now rule out PBHs as the dominant component of dark matter for masses $\sim {10}^{16}–{10}^{17}\mathrm{g}$. Planned MeV gamma-ray observatories are ideal for further improving constraints on PBHs in this mass range.

We provide a parametrization of a new phenomenological scaling function obtained from a chi-square fit to a selected set of $(e,e^{\prime })$ cross section data expanding a band centered around the quasielastic peak. We start from a reanalysis of quasielastic electron scattering from nuclear matter within the relativistic mean field model. The cross section depends on the relativistic effective mass of the nucleon, $m_N^{*}$, and it scales with respect to a new scaling variable, ${\psi }^{*}$. This suggests a new superscaling approach with effective mass for predicting quasielastic cross sections within an uncertainty band. The model reproduces previously established results on the enhancement of the transverse response function as compared to the traditional relativistic Fermi gas.

We investigate decay modes of spin-1 heavy vector bosons ($V^{\prime }$) from the viewpoint of perturbative unitarity in a model-independent manner. Perturbative unitarity requires some relations among couplings. The relations are called unitarity sum rules. We derive the unitarity sum rules from processes that contain two fermions and two gauge bosons. We find the relations between $V^{\prime }$ couplings to the SM fermions ($f$) and $V^{\prime }$ couplings to the SM gauge bosons ($V$). Using the coupling relations, we calculate partial decay widths for $V^{\prime }$ decays into $VV$ and $ff$. We show that $\mathrm{Br}(W^{\prime }\to WZ)\lesssim 2\%$ in the system that contains $V^{\prime }$ and $CP$-even scalars as well as the SM particles. This result is independent of the number of the $CP$-even scalars. We also show that contributions of $CP$-odd scalars help to make $\mathrm{Br}(W^{\prime }\to WZ)$ larger than $\mathrm{Br}(W^{\prime }\to ff)$ as long as the $CP$-odd scalars couple to both the SM fermions and the SM gauge bosons. The existence of the $CP$-odd scalar couplings is a useful guideline to construct models that predict $\mathrm{Br}(W^{\prime }\to WZ)\gtrsim 2\%$. Our analysis relies only on the perturbative unitarity of $f\overline{f}\to W{W}^{\prime }$. Therefore, our result can be applied to various models.

The Majorana nature of neutrinos is one of the most fundamental questions in particle physics. It is directly related to the violation of accidental lepton number symmetry. This motivated enormous efforts into the search of such processes; among them, one conventional experiment is the neutrinoless double-beta decay ($0\nu \beta \beta$). On the other hand, there have been proposals of future electron-positron colliders as a “Higgs factory" for the precise measurement of Higgs boson properties, and it has been proposed to convert such a machine into an electron-electron collider. This option enables a new way to probe TeV Majorana neutrinos via the inverse $0\nu \beta \beta$ decay process ($e^{-}{e}^{-}\to W^{-}{W}^{-}$) as an alternative and complementary test to the conventional $0\nu \beta \beta$ decay experiments. In this paper, we investigate the collider search for $e^{-}{e}^{-}\to W^{-}{W}^{-}$ in different decay channels at future electron colliders. We find that the pure hadronic channel, the semileptonic channel with a muon, and the pure leptonic channel with a dimuon have the most discovery potential.