Constraints to the parameters of inflation models are often derived assuming some plausible range for the number—e.g., $N_k=46$ to $N_k=60$—of $e$-folds of inflation that occurred between the time that our current observable Universe exited the horizon and the end of inflation. However, that number is, for any specific inflaton potential, related to an effective equation-of-state parameter $w_{\text{re}}$ and temperature $T_{\text{re}}$, for reheating. Although the physics of reheating is highly uncertain, there is a finite range of reasonable values for $w_{\text{re}}$. Here we show that, by restricting $w_{\text{re}}$ to this range, more stringent constraints to inflation-model parameters can be derived than those obtained from the usual procedure. To do so, we focus in this work in particular on natural inflation and inflation with a Higgs-like potential and on power-law models as limiting cases of those. As one example, we show that the lower limit to the tensor-to-scalar ratio $r$, derived from current measurements of the scalar spectral index, is about 20%–25% higher (depending on the model) with this procedure than with the usual approach.

We study the structure factors for spin-independent WIMP scattering off xenon based on state-of-the-art large-scale shell-model calculations, which are shown to yield a good spectroscopic description of all experimentally relevant isotopes. Our results are based on the leading scalar one-body currents only. At this level and for the momentum transfers relevant to direct dark matter detection, the structure factors are in very good agreement with the phenomenological Helm form factors used to give experimental limits for WIMP-nucleon cross sections. In contrast to spin-dependent WIMP scattering, the spin-independent channel, at the one-body level, is less sensitive to nuclear structure details. In addition, we explicitly show that the structure factors for inelastic scattering are suppressed by $\sim 10^{-4}$ compared to the coherent elastic scattering response. This implies that the detection of inelastic scattering will be able to discriminate clearly between spin-independent and spin-dependent scattering. Finally, we provide fits for all calculated structure factors.

Galaxy rotation curves determined observationally out to a radius well beyond the galaxy cores can provide a critical test of modified gravity models without dark matter. The predicted rotational velocity curve obtained from scalar-vector-tensor gravity is in excellent agreement with data for the Milky Way without a dark matter halo, with a mass of $5\times 10^{10}{M}_{\odot }$. The velocity rotation curve predicted by modified Newtonian dynamics does not agree with the data.

Quasidilaton massive gravity offers a physically well-defined gravitational theory with nonzero graviton mass. We present the full set of dynamical equations governing the expansion history of the Universe, valid during radiation domination, matter domination, and a late-time self-accelerating epoch related to the graviton mass. The existence of self-consistent solutions constrains the amplitude of the quasidilaton field and the graviton mass, as well as other model parameters. We point out that the effective mass of gravitational waves can be significantly larger than the graviton mass, opening the possibility that a single theory can explain both the late-time acceleration of cosmic expansion and modifications of structure growth leading to the suppression of large-angle correlations observed in the cosmic microwave background.

In the framework of a 3-3-1 model with a minimal scalar sector, known as the economical 3-3-1 model, we study its capabilities of generating realistic quark masses. After a detailed study of the symmetries of the model, before and after the spontaneous symmetry breaking, we find a remaining axial symmetry that prevents some quarks from gaining mass at all orders in perturbation theory. Since this accidental symmetry is anomalous, we also consider briefly the possibility of generating their masses for nonperturbative effects. However, we find that nonperturbative effects are not enough to generate the measured masses for the three massless quarks. Hence, these results imply that the economical 3-3-1 model is not a realistic description of the electroweak interaction.

Nonstandard on-shell decays of $W^{\pm }$ and $Z$ bosons are possible within the framework of extended supersymmetric models, i.e., with singlet states and/or new couplings compared to the minimal supersymmetric standard model. These modes are typically encountered in regions of the parameter space with light singlet-like scalars, pseudoscalars, and neutralinos. In this letter we emphasize how these states can lead to novel signals at colliders from $Z$- or $W^{\pm }$-boson decays with prompt or displaced multileptons/tau jets/jets/photons in the final states. These new modes would give distinct evidence of new physics even when direct searches remain unsuccessful. We discuss the possibilities of probing these new signals using the existing LHC run-I data set. We also address the same in the context of the LHC run-II, as well as for the future colliders. We exemplify our observations with the “$\mu$ from $\nu$” supersymmetric standard model, where three generations of right-handed neutrino superfields are used to solve shortcomings of the minimal supersymmetric standard model. We also extend our discussion for other variants of supersymmetric models that can accommodate similar signatures.

We update the phenomenology of gauge-singlet extensions of the Standard Model scalar sector and their implications for the electroweak phase transition. Considering the introduction of one real scalar singlet to the scalar potential, we analyze present constraints on the potential parameters from Higgs coupling measurements at the Large Hadron Collider (LHC) and electroweak precision observables for the kinematic regime in which no new scalar decay modes arise. We then show how future precision measurements of Higgs boson signal strengths and the Higgs self-coupling could probe the scalar potential parameter space associated with a strong first-order electroweak phase transition. We illustrate using benchmark precision for several future collider options, including the high-luminosity LHC, the International Linear Collider, Triple-Large Electron-Positron collider, the China Electron-Positron Collider, and a 100 TeV proton-proton collider, such as the Very High Energy LHC or the Super Proton-Proton Collider. For the regions of parameter space leading to a strong first-order electroweak phase transition, we find that there exists considerable potential for observable deviations from purely Standard Model Higgs properties at these prospective future colliders.

This article gives details of our proposal to replace ordinary chiral $SU(3{)}_L\times SU(3{)}_R$ perturbation theory $\chi {\mathrm{PT}}_3$ by three-flavor chiral-scale perturbation theory $\chi {\mathrm{PT}}_{\sigma }$. In $\chi {\mathrm{PT}}_{\sigma }$, amplitudes are expanded at low energies and small $u,d,s$ quark masses about an infrared fixed point ${\alpha }_{\mathrm{IR}}$ of three-flavor QCD. At ${\alpha }_{\mathrm{IR}}$, the quark condensate $⟨\overline{q}q{⟩}_{\text{vac}}\ne 0$ induces nine Nambu-Goldstone bosons: $\pi ,K,\eta$, and a $0^{++}$ QCD dilaton $\sigma$. Physically, $\sigma$ appears as the $f_0(500)$ resonance, a pole at a complex mass with real part $\lesssim \hspace{0.17em}{m}_K$. The $\mathrm{\Delta }I=1/2$ rule for nonleptonic $K$ decays is then a consequence of $\chi {\mathrm{PT}}_{\sigma }$, with a $K_S\sigma$ coupling fixed by data for $\gamma \gamma \to \pi \pi$ and $K_S\to \gamma \gamma$. We estimate $R_{\mathrm{IR}}\approx 5$ for the nonperturbative Drell-Yan ratio $R=\sigma (e^{+}{e}^{-}\to \text{hadrons})/\sigma (e^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-})$ at ${\alpha }_{\mathrm{IR}}$ and show that, in the many-color limit, $\sigma /f_0$ becomes a narrow $q\overline{q}$ state with planar-gluon corrections. Rules for the order of terms in $\chi {\mathrm{PT}}_{\sigma }$ loop expansions are derived in Appendix A and extended in Appendix B to include inverse-power Li-Pagels singularities due to external operators. This relates to an observation that, for $\gamma \gamma$ channels, partial conservation of the dilatation current is not equivalent to $\sigma$-pole dominance.

By applying the collinear expansion to the semi-inclusive hadron production process $e^{+}+e^{-}\to h+\overline{q}(\text{jet})+X$ at high energies, we construct a theoretical framework where leading and higher twist contributions at the leading perturbative QCD can be calculated systematically. With this framework, we calculate the contributions up to twist-3 for spin-0, spin-$1/2$, and spin-1 hadrons, respectively. We present the results for the hadronic tensors, the differential cross sections, the azimuthal asymmetries, and the polarizations of the hadrons.

We discuss the sensitivity of a 100 TeV $pp$ collider to heavy particles decaying to top-antitop $(t\overline{t})$ final states. This center-of-mass energy, together with an integrated luminosity of $10{\mathrm{ab}}^{-1}$, can produce heavy particles in the mass range of several tens of teraelectronvolts (TeV). A Monte Carlo study is performed using boosted-top techniques to reduce QCD background for the reconstruction of heavy particles with masses in the range of 8–20 TeV, and various widths. In particular, we study two models that predict heavy states, a model with an extra gauge boson (${\mathrm{Z}}^{0\prime }$) and with a Kaluza-Klein (KK) excitation of the gluon (${\mathrm{g}}_{\mathrm{KK}}$). We estimate the sensitive values of $\sigma \times \mathrm{Br}$ of about 2 (4) fb for ${\mathrm{Z}}^{0\prime }$ (${\mathrm{g}}_{\mathrm{KK}}$), with a corresponding mass reach of 13 (20) TeV.

In a covariant Bethe-Salpeter-equation approach and with a rainbow-ladder truncated model of quantum chromodynamics (QCD), we investigate the use of an effective interaction with the goal of reproducing QCD phenomenology. We extend previous studies and present results for ground and excited meson states in the bottomonium and charmonium systems, where the results are surprisingly good for most states. In addition, we formulate a critical outlook on states with exotic quantum numbers as well as the light-quark domain.

We report the results of a theoretical study of quasielastic electron and neutrino interactions with carbon. Our approach takes into account the effects of final-state interactions between the struck nucleon and the residual nucleus, neglected in the impulse approximation, through a generalization of the spectral function formalism. The calculated electron-scattering cross sections turn out to be in very good agreement with the available data over a broad kinematical region. The impact of nuclear effects on the reconstruction of neutrino energy in charged-current quasielastic processes is also studied, and the results of our approach are compared to the predictions of the relativistic Fermi gas model, routinely employed in most Monte Carlo simulations. Finally, we discuss the limitations of the existing procedure for energy reconstruction and propose a new, improved, one. At energy $\sim 600\mathrm{MeV}$, we observe a sizable difference between neutrino and antineutrino scattering, important for the measurements of charge-parity symmetry violation. Our analysis suggests that a reliable determination of neutrino energy can only be obtained from models validated by a systematic comparison to the available electron-scattering data.

Magnetic fields produced in collisions of electrically charged particles at relativistic energies are strong enough to affect the dynamics of the strong interactions. In particular, it induces radiation of vector bosons by relativistic fermions. I calculate the corresponding spectrum in constant magnetic field and analyze its angular distribution and mass dependence. As an application, synchrotron radiation of vector bosons by relativistic plasmas is considered.

Low energy neutrino astronomy (LENA) has been proposed as a next generation 50 kt liquid scintillator detector. Its large target mass allows us to search for the diffuse supernova neutrino background (DSNB), which was generated by the cumulative emissions of all core-collapse supernovae throughout the Universe. Indistinguishable background from reactor and atmospheric electron antineutrinos limits the detection window to the energy range between 9.5 MeV and 25 MeV. Depending on the mean supernova neutrino energy, about 5 to 10 events per year are expected in this energy window. The background from neutral current reactions of atmospheric neutrinos surpasses the DSNB by more than one order magnitude, but can be suppressed by pulse shape discrimination. Assuming that the residual background is known with 5% uncertainty, the DSNB can be detected with $3\sigma$ significance after 10 years of data taking. In case no hint for a signal is seen, the allowed parameter space of DSNB models would be substantially constrained and the currently favored predictions for spectral mean energy and supernova rate would be excluded with more than 90% C.L.

We study the Hawking-Page transition in a holographic model of field theories with momentum dissipation. We find that the deconfinement temperature strictly decreases as momentum dissipation is increased. For sufficiently strong momentum dissipation, the critical temperature goes to zero, indicating a zero-temperature deconfinement transition in the dual field theory.

We construct a D-brane soliton, a composite topological soliton sharing some properties with a D-brane, in a Skyrme model in $4+1$ dimensions, in which Skyrmions are strings ending on a domain wall. We further generalize this D-brane soliton to diverse dimensions. A string, carrying the ${\pi }_{N-1}$ topological charge, ends on a domain wall in an $\mathrm{O}(N)$ model with higher-derivative terms in $N+1$ dimensions.

We investigate low-energy limits of massive gauge theories that feature the Vainshtein mechanism, focusing on the effects of the UV modes that are integrated out. It turns out that the Goldstone sectors are significantly influenced by the effects from such modes relative to the effective field theories where the irrelevant operators induced by heavy modes are simply cast aside. The effects of the consistently retained higher-order corrections affect the strong coupling and show that the nature of the UV completion influences the low-energy theory significantly. This casts doubts on the naively estimated environmental strong coupling scale, and on the effectiveness of the environmental enhancement of screening. The environmental effects by themselves might not suffice to cure the bad behavior of the theory beyond the vacuum cutoff.

We semiclassically investigate Schwinger pair production for pulsed rotating electric fields depending on time. To do so we solve the Dirac equation for two-component fields in a Wentzel–Kramers–Brillouin-like approximation. The result shows that for two-component fields the spin distribution of produced pairs is generally not $1:1$. As a result the pair creation rates of spinor and scalar QED are different even for one pair of turning points. For rotating electric fields, the pair creation rate is dominated by particles with a specific spin depending on the sense of rotation for a certain range of pulse lengths and frequencies. We present an analytical solution for the momentum spectrum of the constant rotating field. We find interference effects not only in the momentum spectrum but also in the total particle number of rotating electric fields.