We extend the chameleon models by considering scalar-fluid theories where the coupling between matter and the scalar field can be represented by a quadratic effective potential with density-dependent minimum and mass. In this context, we study the effects of the scalar field on Solar System tests of gravity and show that models passing these stringent constraints can still induce large modifications of Newton’s law on galactic scales. On these scales we analyze models which could lead to a percent deviation of Newton’s law outside the virial radius. We then model the dark matter halo as a Navarro-Frenk-White profile and explicitly find that the fifth force can give large contributions around the galactic core in a particular model where the scalar field mass is constant and the minimum of its potential varies linearly with the matter density. At cosmological distances, we find that this model does not alter the growth of large scale structures and therefore would be best tested on galactic scales, where interesting signatures might arise in the galaxy rotation curves.

We explicitly confirm that spatially flat nonsingular bouncing cosmologies make sense as effective theories. The presence of a nonsingular bounce in a spatially flat universe implies a temporary violation of the null energy condition, which can be achieved through a phase of ghost condensation. We calculate the scale of strong coupling and demonstrate that the ghost–condensate bounce remains trustworthy throughout, and that all perturbation modes within the regime of validity of the effective description remain under control. For this purpose we require the perturbed action up to third order in perturbations, which we calculate in both flat and co-moving gauge—since these two gauges allow us to highlight different physical aspects. Our conclusion is that there exist healthy descriptions of nonsingular bouncing cosmologies providing a viable resolution of the big-bang singularities in cosmological models. Our results also suggest a variant of ekpyrotic cosmology, in which entropy perturbations are generated during the contracting phase, but are only converted into curvature perturbations after the bounce.

We study hypermagnetic helicity and lepton asymmetry evolution in the plasma of the early Universe before the electroweak phase transition accounting for chirality flip processes via inverse Higgs decays and sphaleron transitions which violate the left lepton number and wash out the baryon asymmetry of the Universe (BAU). In the scenario where the right electron asymmetry supports the BAU alone through the conservation law $B/3-L_{eR}=\text{const}$ at temperatures $T>T_{\mathrm{RL}}\simeq 10\mathrm{TeV}$, the following Universe cooling leads to the production of a nonzero left lepton (electrons and neutrinos) asymmetry. This is due to the Higgs decays becoming faster when entering the equilibrium at $T=T_{\mathrm{RL}}$, with the Universe expansion, ${\mathrm{\Gamma }}_{\mathrm{RL}}\sim T>H\sim T^2$, resulting in the parallel evolution of the right and left electron asymmetries at $T<T_{\mathrm{RL}}$ through the corresponding Abelian anomalies in the standard model in the presence of a seed hypermagnetic field. The hypermagnetic helicity evolution proceeds in a self-consistent way with the lepton asymmetry growth. The role of sphaleron transitions in decreasing the left lepton number turns out to be negligible in a given scenario. The hypermagnetic helicity plays a key role in lepto-/baryogenesis in our scenario, and the more hypermagnetic field gets closer to the maximum helical one the faster the BAU grows to the observable value, $B_{\text{obs}}\sim 10^{-10}$.

It is well known that one cannot apply a conformal transformation to $f(T)$ gravity to obtain a minimally coupled scalar field model, and thus no Einstein frame exists for $f(T)$ gravity. Furthermore nonminimally coupled “teleparallel dark energy models” are not conformally equivalent to $f(T)$ gravity. However, it can be shown that $f(T)$ gravity is conformally equivalent to a teleparallel phantom scalar field model with a nonminimal coupling to a boundary term only. In this work, we extend this analysis by considering a recently studied extended class of models, known as $f(T,B)$ gravity, where $B$ is a boundary term related to the divergence of a contraction of the torsion tensor. We find that nonminimally coupled “teleparallel dark energy models” are conformally equivalent to either an $f(T,B)$ or $f(B)$ gravity model. Finally conditions on the functional form of $f(T,B)$ gravity are derived to allow it to be transformed to particular nonminimally coupled scalar field models.

Bound, antibound and resonance states are associated to poles in the on-shell partial wave amplitudes. We show here that from the residues of the pole a rank 1 projection operator associated with any of these states can be extracted, in terms of which a sum rule related to the composition of the state can be derived. Although typically it involves complex coefficients for the compositeness and elementariness, except for the bound state case, we demonstrate that one can formulate a meaningful compositeness relation with only positive coefficients for resonances whose associated Laurent series in the variable $s$ converges in a region of the physical axis around $\mathrm{Re}{s}_P$, with $s_P$ the pole position of the resonance. It is also shown that this result can be considered as an analytical extrapolation in $s_P$ of the clear narrow resonance case. We exemplify this formalism to study the two-body components of several resonances of interest.

Missing energy signals such as monojets are a possible signature of dark matter (DM) at colliders. However, neutrino interactions beyond the Standard Model may also produce missing energy signals. In order to conclude that new “missing particles” are observed, the hypothesis of beyond the Standard Model neutrino interactions must be rejected. In this paper, we first derive new limits on these nonstandard neutrino interactions (NSIs) from LHC monojet data. For heavy NSI mediators, these limits are much stronger than those coming from traditional low-energy $\nu$ scattering or $\nu$ oscillation experiments for some flavor structures. Monojet data alone can be used to infer the mass of the missing particle from the shape of the missing energy distribution. In particular, 13 TeV LHC data will have sensitivity to DM masses greater than $\sim 1\mathrm{TeV}$. In addition to the monojet channel, NSI can be probed in multilepton searches which we find to yield stronger limits at heavy mediator masses. The sensitivity offered by these multilepton channels provides a method to reject or confirm the DM hypothesis in missing energy searches.

We consider the phase diagram of twisted-mass Wilson fermions of two-flavor QCD in the parameter space of the quark mass, the isospin chemical potential, the twist angle and the lattice spacing. This work extends earlier studies in the continuum and those at zero chemical potential. We evaluate the phase diagram as well as the spectrum of the (pseudo-)Goldstone bosons using the chiral Lagrangian for twisted-mass Wilson fermions at nonzero isospin chemical potential. The phases are obtained from a mean field analysis. At zero twist angle we find that already an infinitesimal isospin chemical potential destroys the Aoki phase. The reason is that in this phase we have massless Goldstone bosons with a nonzero isospin charge. At finite twist angle, only two different phases are present—one phase which is continuously connected to the Bose condensed phase at nonzero chemical potential, and another phase which is continuously connected to the normal phase. For either zero or maximal twist, the phase diagram is more complicated, as the saddle-point equations allow for more solutions.

We calculate the spectrum of transfer matrix eigenvalues associated with Polyakov loops in finite-density lattice QCD with static quarks. These eigenvalues determine the spatial behavior of Polyakov loop correlation functions. Our results are valid for all values of the gauge coupling in $1+1$ dimensions and in the strong-coupling region for any number of dimensions. When the quark chemical potential $\mu$ is nonzero, the spatial transfer matrix $T_s$ is non-Hermitian. The appearance of complex eigenvalues in $T_s$ is a manifestation of the sign problem in finite-density QCD. The invariance of finite-density QCD under the combined action of charge conjugation $\mathcal{C}$ and complex conjugation $\mathcal{K}$ implies that the eigenvalues of $T_s$ are either real or part of a complex pair. Calculation of the spectrum confirms the existence of complex pairs in much of the temperature-chemical potential plane. Many features of the spectrum for static quarks are determined by a particle-hole symmetry. For $\mu$ that is small compared to the quark mass $M$, we typically find real eigenvalues for the lowest-lying states. At somewhat larger values of $\mu$, pairs of eigenvalues may form complex-conjugate pairs, leading to damped oscillatory behavior in Polyakov loop correlation functions. However, near $\mu =M$, the low-lying spectrum becomes real again. This is a direct consequence of the approximate particle-hole symmetry at $\mu =M$ for heavy quarks. This behavior of the eigenvalues should be observable in lattice simulations and can be used as a test of lattice algorithms. Our results provide independent confirmation of results we have previously obtained in Polyakov-Nambu-Jona-Lasinio models using complex saddle points.

We argue that a hidden-charm pentaquark recently observed in weak decays of ${\mathrm{\Lambda }}_b$ can be produced in proton-nucleus collisions without electroweak intermediaries. We analyze the production cross section for the case when a pentaquark is a molecule of charmonium and a light baryon, as suggested by some models of pentaquark structure, and find that the cross section is sizable. This process can be studied both in collider and in fixed-target experiments. In the former case, the pentaquarks are produced at very forward rapidities, whereas in the latter case, pentaquarks are produced with relatively small rapidities and can be easily detected via invariant mass distribution of a forward $J/\psi$ and a comoving proton. Additionally, the suggested process allows us to check the existence of a neutral pentaquark $P_c^0$ (an isospin partner of $P_c^{+}$) predicted in several models. The rapidity and transverse momentum distributions of pentaquarks could provide comprehensive information about the $\overline{c}c$ component of this exotic baryon.

We solve the Balitsky-Kovchegov evolution equation at next-to-leading order accuracy including a resummation of large single and double transverse momentum logarithms to all orders. We numerically determine an optimal value for the constant under the large transverse momentum logarithm that enables including a maximal amount of the full NLO result in the resummation. When this value is used, the contribution from the ${\alpha }_{\mathrm{s}}^2$ terms without large logarithms is found to be small at large saturation scales and at small dipoles. Close to initial conditions relevant for phenomenological applications, these fixed-order corrections are shown to be numerically important.

In this work, we investigate the mass corrections of the doubly charmed baryons up to $N^{2}LO$ in the extended-on-mass-shell (EOMS) renormalization scheme, comparing with the results of heavy baryon chiral perturbation theory. We find that the terms from the heavy baryon approach are a subset of those obtained in the EOMS scheme. By fitting the lattice data, we can determine the parameters $\tilde{m}$, $\alpha$, $c_1$ and $c_7$ from the Lagrangian, while in the heavy baryon approach no information on $c_1$ can be obtained from the baryons mass. Correspondingly, the masses of $m_{{\mathrm{\Xi }}_{cc}}$ and $m_{{\mathrm{\Omega }}_{cc}}$ are predicted, in the EOMS scheme, extrapolating the results from different values of the charm quark and the pion masses of the lattice QCD calculations.

We study here the ${\mathrm{\Lambda }}_b^0\to J/\psi p{\pi }^{-}$ reaction in analogy to the ${\mathrm{\Lambda }}_b^0\to J/\psi p{K}^{-}$ one, and we note that in both decays there is a sharp structure (dip or peak) in the $J/\psi p$ mass distribution around 4450 MeV, which is associated in the ${\mathrm{\Lambda }}_b^0\to J/\psi p{K}^{-}$ experiment to an exotic pentaquark baryonic state, although in ${\mathrm{\Lambda }}_b^0\to J/\psi p{\pi }^{-}$ it shows up with relatively low statistics. We analyze the ${\mathrm{\Lambda }}_b^0\to J/\psi p{\pi }^{-}$ interaction along the same lines as the ${\mathrm{\Lambda }}_b^0\to J/\psi p{K}^{-}$ one, with the main difference stemming from the reduced Cabibbo strength in the former and the consideration of the ${\pi }^{-}p$ final state interaction instead of the $K^{-}p$ one. We find that with a minimal input, introducing the ${\pi }^{-}p$ and $J/\psi p$ interaction in $S$-wave with realistic interactions, and the empirical $P$-wave and $D$-wave contributions, one can accomplish a qualitative description of the ${\pi }^{-}p$ and $J/\psi p$ mass distributions. More importantly, the peak structure followed by a dip of the experimental $J/\psi p$ mass distribution is reproduced with the same input as used to describe the data of ${\mathrm{\Lambda }}_b^0\to J/\psi p{K}^{-}$ reaction. The repercussion for the triangular singularity mechanism, invoked in some works to explain the pentaquark peak, is discussed.

We consider a scenario where, along with the usual Higgs doublet, two scalar triplets are present. The extension of the triplet sector is required for the Type II seesaw mechanism for the generation of neutrino masses, if this mechanism has to generate a neutrino mass matrix with two-zero texture. One $CP$-violating phase has been retained in the scalar potential of the model, and all parameters have been chosen consistently with the observed neutrino mass and mixing patterns. We find that a large phase ($\gtrsim 60°$) splits the two doubly charged scalar mass eigenstates wider apart, so that the decay $H_1^{++}\to H_2^{++}h$ is dominant (with $h$ being the 125 GeV scalar). We identify a set of benchmark points where this decay dominates. This is complementary to the situation, reported in our earlier work, where the heavier doubly charged scalar decays as $H_1^{++}\to H_2^{+}{W}^{+}$. We point out the rather spectacular signal, ensuing from $H_1^{++}\to H_2^{++}h$, in the form of Higgs plus the same-sign dilepton peak, which can be observed at the Large Hadron Collider.

A simultaneous fit of parton distribution functions (PDFs) and electroweak parameters to HERA data on deep inelastic scattering is presented. The input data are the neutral current and charged current inclusive cross sections which were previously used in the QCD analysis leading to the HERAPDF2.0 PDFs. In addition, the polarization of the electron beam was taken into account for the ZEUS data recorded between 2004 and 2007. Results on the vector and axial-vector couplings of the $Z$ boson to $u$- and $d$-type quarks, on the value of the electroweak mixing angle and the mass of the $W$ boson are presented. The values obtained for the electroweak parameters are in agreement with Standard Model predictions.

We studied the effect of finite quark mass on the dynamics of the axial charge using the D3/D7 model in holography. The mass term in the axial anomaly equation affects both the fluctuation (generation) and dissipation of the axial charge. We studied the dependence of the effect on quark mass and an external magnetic field. For axial charge generation, we calculated the mass diffusion rate, which characterizes the helicity flipping rate. The rate is a nonmonotonous function of mass and can be significantly enhanced by the magnetic field. The diffusive behavior is also related to a divergent susceptibility of the axial charge. For axial charge dissipation, we found that in the long time limit, the mass term dissipates all the charge effectively generated by parallel electric and magnetic fields. The result is consistent with a relaxation time approximation. The rate of dissipation through mass term is a monotonous increasing function of both quark mass and a magnetic field.

Inspired by a recent ghost-free nonlinear massive gravity in four-dimensional spacetime, we study its higher dimensional scenarios. As a result, we are able to show the constantlike behavior of massive graviton terms for some well-known metrics such as the Friedmann-Lemaitre-Robertson-Walker, Bianchi type I, and Schwarzschild-Tangherlini (anti-) de Sitter metrics in a specific five-dimensional nonlinear massive gravity under an assumption that its fiducial metrics are compatible with physical ones. In addition, some simple cosmological solutions of the five-dimensional massive gravity are figured out consistently.

We present a new hybrid Cauchy-characteristic evolution scheme that is particularly suited to study gravitational collapse in spherically symmetric asymptotically (global) anti-de Sitter (AdS) spacetimes. The Cauchy evolution allows us to track the scalar field through the different round trips to the AdS boundary, while the characteristic method can bring us very close to the point of formation of an apparent horizon. We describe all the details of the method, including the transition between the two evolution schemes and the details of the numerical implementation for the case of massless scalar fields. We use this scheme to provide more numerical evidence for a recent conjecture on the power law scaling of the apparent horizon mass resulting from the collapse of subcritical configurations. We also compute the critical exponents and echoing periods for a number of critical points and confirm the expectation that their values should be the same as in the asymptotically flat case.

We show that if the new physics beyond the standard model is associated with a first-order phase transition around ${10}^7–{10}^8\mathrm{GeV}$, the energy density stored in the resulting stochastic gravitational waves and the corresponding peak frequency are within the projected final sensitivity of the advanced LIGO/VIRGO detectors. We discuss some possible new physics scenarios that could arise at such energies, and in particular, the consequences for Peccei-Quinn and supersymmetry breaking scales.