We present the QCD simulation of the first gauge ensemble of two degenerate light quarks, a strange and a charm quark with all quark masses tuned to their physical values within the twisted mass fermion formulation. Results for the pseudoscalar masses and decay constants confirm that the produced ensemble is indeed at the physical parameters of the theory. This conclusion is corroborated by a complementary analysis in the baryon sector. We examine cutoff and isospin breaking effects and demonstrate that they are suppressed through the presence of a clover term in the action.

We calculate the up-, down-, strange-, charm-, and bottom-quark masses using the MILC highly improved staggered-quark ensembles with four flavors of dynamical quarks. We use ensembles at six lattice spacings ranging from $a\approx 0.15$ to 0.03 fm and with both physical and unphysical values of the two light and the strange sea-quark masses. We use a new method based on heavy-quark effective theory (HQET) to extract quark masses from heavy-light pseudoscalar meson masses. Combining our analysis with our separate determination of ratios of light-quark masses we present masses of the up, down, strange, charm, and bottom quarks. Our results for the $\overline{\mathrm{MS}}$-renormalized masses are $m_u(2\mathrm{GeV})=2.130(41)\mathrm{MeV}$, $m_d(2\mathrm{GeV})=4.675(56)\mathrm{MeV}$, $m_s(2\mathrm{GeV})=92.47(69)\mathrm{MeV}$, $m_c(3\mathrm{GeV})=983.7(5.6)\mathrm{MeV}$, and $m_c(m_c)=1273(10)\mathrm{MeV}$, with four active flavors; and $m_b(m_b)=4195(14)\mathrm{MeV}$ with five active flavors. We also obtain ratios of quark masses $m_c/m_s=11.783(25)$, $m_b/m_s=53.94(12)$, and $m_b/m_c=4.578(8)$. The result for $m_c$ matches the precision of the most precise calculation to date, and the other masses and all quoted ratios are the most precise to date. Moreover, these results are the first with a perturbative accuracy of ${\alpha }_s^4$. As byproducts of our method, we obtain the matrix elements of HQET operators with dimension 4 and 5: ${\overline{\mathrm{\Lambda }}}_{\mathrm{MRS}}=555(31)\mathrm{MeV}$ in the minimal renormalon-subtracted (MRS) scheme, ${\mu }_{\pi }^2=0.05(22){\mathrm{GeV}}^2$, and ${\mu }_G^2(m_b)=0.38(2){\mathrm{GeV}}^2$. The MRS scheme [Phys. Rev. D 97, 034503 (2018)] is the key new aspect of our method.

We present a detailed phenomenological study of polarized inclusive jet production in electron-proton collisions at a future Electron-Ion Collider (EIC). Our analysis is performed at next-to-leading order in perturbative QCD using the numerical code DISTRESS and includes all relevant partonic channels and resolved photon contributions. We elucidate the role of different kinematic regions in probing different aspects of proton and photon structure. We emphasize the importance of inclusive jet measurements and high collision energies at a future EIC in order to further constrain the polarized gluon distribution of the proton.

We consider processes where an electroweak gauge boson ($W$ or $Z$) is produced in the decays of a heavy fermion. The polarization state of the produced gauge boson is given in terms of a vector polarization and a rank-2 tensor polarization. In the rest frame of the mother fermion, these are given directly by the dynamical parameters of the underlying theory. In a frame where the mother particle is moving, the polarization parameters of the gauge boson are dependent additionally upon kinematical factors. We show that these kinematical factors depend only on the magnitude of the velocity of the mother particle and derive analytical expressions for them. We apply the results to pair production of heavy fermions at the LHC with one of the fermions decaying to a gauge boson ($W$, $Z$) and a light Standard Model fermion. We construct estimators of laboratory frame values of polarization parameters of the produced gauge boson. These estimators can be used to estimate the laboratory frame values of polarization parameters of the produced gauge boson without a detailed simulation of the entire process. We validate our expressions with detailed Monte Carlo simulations in the context of beyond the Standard Model scenarios which have a vectorlike top partner. We also indicate how to include finite width effects of the heavy fermion in some special cases.

The exclusive reaction $\gamma p\to p{K}^{+}{K}^{-}$ was studied in the photon energy range $3.0–3.8\mathrm{GeV}$ and momentum transfer range $0.6<-t<1.3{\mathrm{GeV}}^2$. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately $20{\mathrm{pb}}^{-1}$. The reaction was isolated by detecting the $K^{+}$ and the proton in CLAS, and reconstructing the $K^{-}$ via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the $\varphi$ meson in the $P$ wave, evidence for $S-P$ interference was found. The differential production cross sections $d\sigma /dt$ for individual waves in the mass range of the $\varphi$ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the $t$-dependent cross section of the $S$-wave contribution to the elastic $K^{+}{K}^{-}$ photoproduction has been measured.

Wormhole solutions in a generalized hybrid metric-Palatini matter theory, given by a gravitational Lagrangian $f(R,\mathcal{R})$, where $R$ is the metric Ricci scalar, and $\mathcal{R}$ is a Palatini scalar curvature defined in terms of an independent connection, and a matter Lagrangian, are found. The solutions are worked in the scalar-tensor representation of the theory, where the Palatini field is traded for two scalars, $\phi$ and $\psi$, and the gravitational term $R$ is maintained. The main interest in the solutions found is that the matter field obeys the null energy condition (NEC) everywhere, including the throat and up to infinity, so that there is no need for exotic matter. The wormhole geometry with its flaring out at the throat is supported by the higher-order curvature terms, or equivalently, by the two fundamental scalar fields, which either way can be interpreted as a gravitational fluid. Thus, in this theory, in building a wormhole, it is possible to exchange the exoticity of matter by the exoticity of the gravitational sector. The specific wormhole displayed, built to obey the matter NEC from the throat to infinity, has three regions, namely, an interior region containing the throat, a thin shell of matter, and a vacuum Schwarzschild anti-de Sitter (AdS) exterior. For hybrid metric-Palatini matter theories this wormhole solution is the first where the NEC for the matter is verified for the entire spacetime keeping the solution under asymptotic control. The existence of this type of solutions is in line with the idea that traversable wormholes bore by additional fundamental gravitational fields, here disguised as scalar fields, can be found without exotic matter. Concomitantly, the somewhat concocted architecture needed to assemble a complete wormhole solution for the whole spacetime may imply that in this class of theories such solutions are scarce.

We prove that a conserved effective energy-momentum tensor for Einstein-Cartan theory can be identified from the Noether identities of the matter Lagrangian, using the torsion field equations relating them. More precisely, this is a one-parameter family labeled by the Immirzi parameter. We use this result and the contorsion description to show that Jacobson’s thermodynamical derivation of the Einstein equations follows as in the metric theory, namely from the equilibrium Clausius relation and the fact that a Killing horizon is metric geodetic. Our derivation works for an arbitrary torsion field. In the course of our discussion we review the laws of black hole mechanics and their dependence on torsion.

We study the generation of electromagnetic fields during inflation when the conformal invariance of Maxwell’s action is broken by the kinetic coupling $f^2(\varphi )F_{\mu \nu }{F}^{\mu \nu }$ of the electromagnetic field to the inflaton field $\varphi$. We consider the case where the coupling function $f(\varphi )$ decreases in time during inflation and, as a result, the electric component of the energy density dominates over the magnetic one. The system of equations which governs the joint evolution of the scale factor, inflaton field, and electric energy density is derived. The backreaction occurs when the electric energy density becomes as large as the product of the slow-roll parameter $\epsilon$ and inflaton energy density, ${\rho }_E\sim \epsilon {\rho }_{\inf }$. It affects the inflaton field evolution and leads to the scale-invariant electric power spectrum and the magnetic one which is blue with the spectral index $n_B=2$ for any decreasing coupling function. This gives an upper limit on the present-day value of observed magnetic fields below ${10}^{-22}\mathrm{G}$. It is worth emphasizing that since the effective electric charge of particles $e_{\mathrm{eff}}=e/f$ is suppressed by the coupling function, the Schwinger effect becomes important only at the late stages of inflation when the inflaton field is close to the minimum of its potential. The Schwinger effect abruptly decreases the value of the electric field, helping to finish the inflation stage and enter the stage of preheating. It effectively produces the charged particles, implementing the Schwinger reheating scenario even before the fast oscillations of the inflaton. The numerical analysis is carried out in the Starobinsky model of inflation for the powerlike $f\propto a^{\alpha }$ and Ratra-type $f=\exp (\beta \varphi /M_p)$ coupling functions.

In this work we investigate the holographic dark energy models with slowly time-varying model parameter defined based on the current Hubble horizon length scale. While the previous studies on the three popular holographic dark energy models defined based on the future event horizon, Ricci scale and Granda-Oliveros IR cutoffs showed that these models cannot fit the observational data [I. A. Akhlaghi, M. Malekjani, S. Basilakos, and H. Haghi, Mon. Not. R. Astron. Soc. 477, 3659 (2018)], in this work we show that the holographic dark energy models with time-varying model parameter defined on the current Hubble radius are well favored by observations. Using the standard ${\chi }^2$ minimization in the context of Markov Chain Monte Carlo method, we compare the ability of holographic dark energy models with time-varying $c^2$ parameter constructed on the current Hubble length scale against different sets of observational data namely expansion data, growth rate data, and $\mathrm{expansion}+\mathrm{growth}$ rate data, respectively. Based on the values of Akaike and Bayesian information criteria, we find that these types of holographic dark energy models are well fitted to both expansion and growth rate observations as equal to $\mathrm{\Lambda }\mathrm{CDM}$ cosmology. We also put constraints on the cosmological parameters and show that the transition epoch form early decelerated to current accelerated expansion calculated in holographic dark energy models with time-varying model parameter defined on the Hubble length is consistent with observations.

Any particle dark matter (DM) scenario featuring a suppressed power spectrum of astrophysical relevance results in a delay of galaxy formation. As a consequence, such scenarios can be constrained using the global 21-cm absorption signal initiated by the UV radiation of the first stars. The Experiment to Detect the Global Epoch of Reionization Signature (EDGES) recently reported the first detection of such an absorption signal at redshift $\sim 17$. While its amplitude might indicate the need for new physics, we solely focus on the timing of the signal to test noncold DM models. Assuming conservative limits for the stellar-to-baryon fraction ($f_{*}<0.03$) and for the minimum cooling temperature ($T_{\mathrm{vir}}>{10}^3$ Kelvin) motivated by radiation-hydrodynamic simulations, we are able to derive unprecedented constraints on a variety of noncold DM models. For example, the mass of thermal warm DM is limited to $m_{\mathrm{TH}}>6.1\mathrm{keV}$, while mixed DM scenarios (featuring a cold and a hot component) are constrained to a hot DM fraction below 17 percent. The ultralight axion DM model is limited to masses $m_a>8\times {10}^{-21}\mathrm{eV}$, a regime where its wave-like nature is pushed far below the kiloparsec scale. Finally, sterile neutrinos from resonant production can be fully disfavored as a dominant DM candidate. The results of this paper show that the 21-cm absorption signal is a powerful discriminant of noncold dark matter, allowing for significant improvements over to the strongest current limits. Confirming the result from EDGES is paramount in this context.

Numerical data of the SU(3) gauge theory with $N_f=8$ fermions in the fundamental representation suggest the existence of a large-mass regime, where the fermion mass is not small relative to the confinement scale, but nevertheless the dilaton-pion low-energy theory is applicable thanks to the parametric proximity of the conformal window. In this regime, the leading hyperscaling relations are similar to those of a mass-deformed conformal theory, so that distinguishing infrared conformality from confinement requires the study of subleading effects. Assuming that the $N_f=8$ theory confines, we estimate how light the fermion mass should be to enter the small-mass regime, where the pions become much lighter than the dilatonic scalar meson.

The vacuum to nuclear matter phase transition is studied in the presence of a constant external background magnetic field with the mean-field approximation in the Walecka model. The anomalous nucleon magnetic moment is taken into account using the modified “weak” field expansion of the fermion propagator with nontrivial correction terms for both charged and neutral particles. The effect of the nucleon magnetic moment is found to favor the magnetic catalysis effect at zero temperature and zero baryon density. However, extending the study to finite temperatures, it is observed that the anomalous nuclear magnetic moment plays a crucial role in characterizing the qualitative behavior of the vacuum to nuclear matter phase transition even in the case of weak external magnetic fields. The critical temperature corresponding to the vacuum to nuclear medium phase transition is observed to decrease with the external magnetic field, which can be identified as inverse magnetic catalysis in the Walecka model, whereas the opposite behavior is obtained in the case of a vanishing magnetic moment, indicating magnetic catalysis.

The critical behavior of a nonlocal scalar field theory is studied. This theory has a nonlocal kinetic term which involves a real power $1-2\alpha$ of the Laplacian. The interaction term is the usual local ${\varphi }^4$ interaction. The lowest order Feynman diagrams corresponding to coupling constant renormalization, mass renormalization, and field renormalization are computed. Particular features appearing in the renormalization of this nonlocal theory that differ from the case of local theories are studied. The previous calculations lead to the perturbative computation of the coupling constant beta function and critical exponents $\nu$ and $\eta$. In four dimensions for $\alpha <0$ this beta function presents asymptotic freedom in the UV. This is remarkable since no non-Abelian vector fields are included. However, this comes at the expense of losing reflection positivity.

The search for singlet fermion dark matter at high-energy colliders is commonly analyzed with a singlet scalar mediator, which however violates the standard model (SM) gauge invariance, renormalizability and unitarity. These problems can be cured by introducing a mixing between the singlet scalar $s$ and the SM Higgs boson $h$. Thus one has to consider two scalar mediators $h_1$ and $h_2$, where $h_1$ is identified as the discovered 125 GeV Higgs boson. As a specific example, we consider the dark matter (DM) search in the $t\overline{t}+{\cancel{E}}_T$ channel. According to the masses of dark matter and two scalar mediators, we classify the process into four cases. By investigating the total cross sections and differential distributions, we find that the contribution of the 125 GeV Higgs boson $h_1$ cannot be neglected in all cases and can even dominate once $h_1$ is on shell in dark matter production. Further, we study the impact of $h_1$ on the LHC bounds of dark matter searches in the hadronic and semileptonic channels with the integrated luminosity of $36{\mathrm{fb}}^{-1}$. Finally we make a brief comment that $h_1$ should be also considered in the vector DM search at high-energy colliders.

In this paper, we investigate the phase structure of the dense quark matter in the presence of baryon ${\mu }_B$, isospin ${\mu }_I$, chiral ${\mu }_5$, and chiral isospin ${\mu }_{I5}$ chemical potentials in the framework of the Nambu–Jona-Lasinio model. We show that, in the large-$N_c$ limit ($N_c$ is the number of quark colors), there exist three duality correspondences in the model. The first duality is between the chiral symmetry breaking and the charged-pion condensation phenomena, and there are two new dualities that hold only for chiral symmetry breaking and charged-pion condensation phenomena separately. These dualities show that chiral symmetry breaking phenomenon does not feel the difference between chiral ${\mu }_5$ and chiral isospin ${\mu }_{I5}$ chemical potentials, and charged-pion condensation phenomenon does not feel the difference between isospin ${\mu }_I$ and chiral ${\mu }_5$ chemical potentials. We show that ${\mu }_5$ can generate charged-pion condensation, but this generation occurs at not so large baryon densities. In the case of both chiral imbalances (chiral ${\mu }_5$ and chiral isospin ${\mu }_{I5}$ chemical potentials), the phase portrait is rather rich, and we show that charged-pion condensation in dense quark matter takes up a large part of the phase diagram. Charged-pion condensation in dense quark matter happens even in the case of zero isospin imbalance and requires only chiral imbalances; this fact can be demonstrated with the use of one of the new dualities and this is only one example of when these dualities are of great use in exploring the phase diagram.

Searches for new heavy resonances decaying into different pairings of $W$, $Z$, or Higgs bosons, as well as directly into leptons, are presented using a data sample corresponding to $36.1{\mathrm{fb}}^{-1}$ of $pp$ collisions at $\sqrt{s}=13\mathrm{TeV}$ collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting bosonic decay modes in the $qqqq$, $\nu \nu qq$, $\ell \nu qq$, $\ell \ell qq$, $\ell \nu \ell \nu$, $\ell \ell \nu \nu$, $\ell \nu \ell \ell$, $\ell \ell \ell \ell$, $qqbb$, $\nu \nu bb$, $\ell \nu bb$, and $\ell \ell bb$ final states are combined, searching for a narrow-width resonance. Likewise, analyses selecting the leptonic $\ell \nu$ and $\ell \ell$ final states are also combined. These two sets of analyses are then further combined. No significant deviation from the Standard Model predictions is observed. Three benchmark models are tested: a model predicting the existence of a new heavy scalar singlet, a simplified model predicting a heavy vector-boson triplet, and a bulk Randall-Sundrum model with a heavy spin-2 Kaluza-Klein excitation of the graviton. Cross section limits are set at the 95% confidence level using an asymptotic approximation and are compared with predictions for the benchmark models. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The data exclude a heavy vector-boson triplet with mass below 5.5 TeV in a weakly coupled scenario and 4.5 TeV in a strongly coupled scenario, as well as a Kaluza-Klein graviton with mass below 2.3 TeV.

We study the free massive scalar field in de Sitter spacetime with static charts. In particular, we find positive-frequency modes for the Bunch-Davies vacuum state natural to the static charts as superpositions of the well-known positive-frequency modes in the conformally-flat chart. We discuss in detail how these modes are defined globally in the two static charts and the region in their future. The global structure of these solutions leads to the well-known description of the Bunch-Davies vacuum state as an entangled state. Our results are expected to be useful not only for studying the thermal properties in the vacuum fluctuations in de Sitter spacetime but also for understanding the nonlocal properties of the vacuum state.

It is known that the two- and three-point functions of Higgs-branch superconformal primaries in 4d $\mathcal{N}=2$ superconformal field theories obey nonrenormalization theorems on $\mathcal{N}=2$ superconformal manifolds. In this paper, we prove a stronger statement—that the bundles of Higgs-branch superconformal primaries over $\mathcal{N}=2$ superconformal manifolds are endowed with a flat connection or, equivalently, that Higgs-branch superconformal primaries have vanishing Berry phases under $\mathcal{N}=2$ exactly marginal deformations. This statement fits well with the proposed correspondence between the rigid structures of two-dimensional chiral algebras and the sector of Schur operators in four-dimensional $\mathcal{N}=2$ theories. We also discuss the general interplay between nonrenormalization theorems and the curvature of bundles of protected operators and provide a new simpler proof of the vanishing curvature of $1/2$-BPS operators in four-dimensional $\mathcal{N}=4$ SYM theory that does not require the use of the four-dimensional $t{t}^{*}$ equations.

We advocate for an alternative description of gravitational radiation from black holes based on complex angular momentum techniques (analytic continuation of partial wave expansions, duality of the $\mathcal{S}$-matrix and effective resummations involving its Regge poles and the associated residues, Regge trajectories, semiclassical interpretations, etc.). Such techniques, which proved to be very helpful in various areas of physics to describe and analyze resonant scattering, were only marginally used in the context of black hole physics. Here, by considering the multipolar waveform generated by a massive particle falling radially from infinity into a Schwarzschild black hole, we show that they could play a fundamental role in gravitational-wave physics. More precisely, from the multipole expansion defining the Weyl scalar ${\mathrm{\Psi }}_4$, we extract the Fourier transform of a sum over Regge poles and their residues, which can be evaluated numerically from the associated Regge trajectories. This Regge pole approximation permits us to reconstruct, for an arbitrary direction of observation, a large part of the multipolar waveform ${\mathrm{\Psi }}_4$. In particular, it can reproduce with very good agreement the quasinormal ringdown as well as with rather good agreement the tail of the signal. This is achieved even if we take into account only one Regge pole, and if a large number of modes are excited, the result can be improved by considering additional poles. Moreover, while quasinormal-mode contributions do not provide physically relevant results at “early times” due to their exponentially divergent behavior as time decreases, it is not necessary to determine from physical considerations a starting time for the Regge ringdown.