In the present work, it is intended to calculate the unintegrated parton distribution functions (UPDFs) of the ${}^{6}Li$ nucleus, which depend not only on the longitudinal momentum fraction $x$ (the Bjorken variable) and the factorization scale $\mu$ of partons, but also on their transverse momentum ($k_t$). Therefore, the KMR and MRW procedures are applied to generate the $k_t$-dependent parton distributions from the familiar integrated parton densities (PDFs), which were determined in our recent related work, using the constituent quark exchange model (CQEM) for the ${}^{6}Li$ nucleus. Then, the resulting UPDFs of ${}^{6}Li$ are compared with the UPDFs of free proton from our previous work. Afterwards, from the $k_t$-factorization formalism, the structure function (SF) of the ${}^{6}Li$ nucleus is computed to extract its European Muon Collaboration (EMC) ratio. The results are compered with those generated from the ${}^{6}Li$ nucleus PDFs and the available NMC experimental data. It is observed that, especially in the small $x$ region, where the $k_t$ dependence of partons is important in the calculations of the hadron structure functions, the present EMC ratios are extremely improved, compared with those of our previous work, and show an excellent agreement with the NMC experimental data.

We perform a systematic study of the modifications to the QCD vacuum energy density ${\epsilon }_{\mathrm{vac}}$ in the zero-temperature case ($T=0$) caused by a small, but nonzero, value of the parameter $\theta$, using different effective Lagrangian models which include the flavor-singlet meson field and implement the $U(1)$ axial anomaly of the fundamental theory. In particular, we derive the expressions for the topological susceptibility $\chi$ and for the second cumulant $c_4$ starting from the $\theta$ dependence of ${\epsilon }_{\mathrm{vac}}(\theta )$ in the various models that we have considered. Moreover, we evaluate numerically our results, so as to compare them with each other, with the predictions of the chiral effective Lagrangian and, finally, also with the available lattice data.

The theory of general relativity first introduced the concept that space-time is curved by the presence of masses. As a consequence, any signal between two sources passing by a massive body is deflected and therefore experiences a transmission time delay with respect to the straight-line propagation. In the parametrized Post-Newtonian formalism—which makes use of a set of post-Newtonian parameters to describe all metric theories of gravitation that assume Einstein equivalence principle—the curvature of space-time is accounted for by the parameter $\gamma$. In general relativity $\gamma$ is equal to unity. The measure of $\gamma$ is one of the most popular general relativity tests that have been undertaken since 1919. The current state-of-the-art measure of $\gamma$ is $\gamma =1+(2.1\pm 2.3)\times {10}^{-5}$, obtained by radio tracking of the NASA/ESA/ASI Cassini-Huygens satellite near solar superior conjunction (Superior Conjunction Experiment—SCE). The ESA/JAXA BepiColombo mission to Mercury will perform a SCE during its cruise-phase. Thanks to a more advanced telecommunication system, made up of a X/X, Ka/Ka, X/Ka multifrequency link, BepiColombo will allow range measurements as accurate as 15 cm at 300 s integration time and range-rate (or Doppler) measurements at the level of $1.5\mu \mathrm{m}/\mathrm{s}$ at 1000 s integration time, one-way. In this work we present the results of the numerical simulations of the BepiColombo SCE with the ORBIT14 orbit determination and parameter estimation software, developed at the University of Pisa. Our software is able to simulate measurements of range and range-rate of the BepiColombo probe during solar superior conjunction and obtain an estimate of $\gamma$ based on a non-linear least squares fit. Through a thorough and complete analysis, which includes the study of the impact of possible systematic errors in the range observables, we show that BepiColombo has the capability to improve the result yielded by Cassini up to a factor 10.

In gravitational collapse leading to black hole formation, trapping horizons typically develop inside the contracting matter. Classically, an ingoing trapping horizon moves toward the center where it reaches a curvature singularity, while an outgoing horizon moves toward the surface of the star where it becomes an isolated, null horizon. However, strong quantum effects at high curvature close to the center could modify the classical picture substantially, e.g., by deflecting the ingoing horizon to larger radii, until it eventually reunites with the outgoing horizon. We here analyze some existing models of regular “black holes” of finite lifespan formed out of ingoing null shells collapsing from ${\mathcal{I}}^{-}$, after giving general conditions for the existence of (singularity-free) closed trapping horizons. We study the energy-momentum tensor of such models by analyzing Einstein’s tensor, which describes the geometry and give an explicit form of the metric to model a Hawking radiation reaching ${\mathcal{I}}^{+}$. A major flaw of the models that aim to describe the formation of black holes (with a Vaidya limit on ${\mathcal{I}}^{-}$) as well as their evaporation is finally exhibited: they necessarily violate the null energy condition up to ${\mathcal{I}}^{-}$, i.e., in a noncompact region of spacetime.

We extend the use of configurational information measures (CIMs) to instantons and vacuum decay in arbitrary spatial dimensions. We find that both the complexity and the information content in the shape of instanton solutions have distinct regions of behavior in parameter space, discriminating between qualitative thin- and thick-wall profiles. For Euclidean spaces of dimension $D$, we show that for $D\ge 6$ instantons undergo a qualitative change of behavior from their lower-dimensional counterparts, indicating that $D=6$ is a critical dimension. We also find a scaling law relating the different CIMs to the rate of vacuum decay, thus connecting the stability of the vacuum to the informational complexity stored in the shape of the related critical bounce.

We study the effect of multiple soft gluon radiation on the kinematical distributions of the $t$-channel single top quark production at the LHC. By applying the transverse momentum-dependent factorization formalism, large logarithms (of the ratio of large invariant mass $Q$ and small total transverse momentum $q_{\perp }$ of the single-top plus one-jet final state system) are resummed to all orders in the expansion of the strong interaction coupling at the accuracy of the next-to-leading logarithm, including the complete next-to-leading-order corrections. We show that the main difference from PYTHIA prediction lies in the inclusion of the exact color coherence effect between the initial and final states in our resummation calculation, which becomes more important when the final state jet is required to be in the forward region. We further propose to apply the experimental observable ${\varphi }^{*}$, similar to the one used in analyzing precision Drell-Yan data, to test the effect of multiple gluon radiation in the single-top events. The effect of the bottom quark mass is also discussed.

We present evidence for the exotic charged charmoniumlike state $Z_c^{\pm }(3900)$ decaying to $J/\psi {\pi }^{\pm }$ in semi-inclusive weak decays of $b$-flavored hadrons. The signal is correlated with a parent $J/\psi {\pi }^{+}{\pi }^{-}$ system in the invariant-mass range 4.2–4.7 GeV that would include the exotic structure $Y(4260)$. The study is based on $10.4{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collision data collected by the D0 experiment at the Fermilab Tevatron collider.

Most of the literature in the bulk reconstruction program in holography focuses on recovering local bulk operators propagating on a quasilocal bulk geometry and the knowledge of the bulk geometry is always assumed or guessed. The fundamental problem of the bulk reconstruction program, which is recovering the bulk background geometry (metric) from the boundary CFT state is still outstanding. In this work, we formulate a recipe to extract the bulk metric itself from the boundary state, specifically, the modular Hamiltonian information of spherical subregions in the boundary. Our recipe exploits the recent construction of Kabat and Lifschytz [J. High Energy Phys. 06 (2017) 120.] to first compute the bulk two point function of scalar fields directly in the CFT without knowledge of the bulk metric or the equations of motion, and then to take a large scaling dimension limit (WKB) to extract the geodesic distance between two close points in the bulk i.e., the metric. As a proof of principle, we consider three dimensional bulk and selected CFT states such as the vacuum and the thermofield double states. We show that they indeed reproduce the pure AdS and the regions outside the Rindler wedge and the BTZ black hole up to a rigid conformal factor. Since our approach does not rely on symmetry properties of the CFT state, it can be applied to reconstruct asymptotically AdS geometries dual to arbitrary general CFT states provided the modular Hamiltonian is available. We discuss several obvious extensions to the case of higher spacetime dimensions as well as some future applications, in particular, for constructing metric beyond the causal wedge of a boundary region. In the process, we also extend the construction of Kabat and Lifschytz [J. High Energy Phys. 06 (2017) 120.] to incorporate the first order perturbative locality for AdS scalars.

Qualitative dynamics of three different loop quantizations of spatially flat isotropic and homogeneous models is studied using an effective spacetime description of the underlying quantum geometry. These include the standard loop quantum cosmology (LQC), its recently revived modification (referred to as mLQC-I), and another related modification of LQC (mLQC-II) of which the dynamics is studied in detail for the first time. Various features of LQC, including quantum bounce and preinflationary dynamics, are found to be shared with the mLQC-I and mLQC-II models. We study universal properties of dynamics for chaotic inflation, fractional monodromy inflation, Starobinsky potential, nonminimal Higgs inflation, and an exponential potential. We find various critical points and study their stability, which reveal various qualitative similarities in the postbounce phase for all these models. The prebounce qualitative dynamics of LQC and mLQC-II turns out to be very similar but is strikingly different from that of mLQC-I. In the dynamical analysis, some of the fixed points turn out to be degenerate. For these fixed points, center manifold theory is used. For all these potentials, nonperturbative quantum gravitational effects always result in a nonsingular inflationary scenario with a phase of superinflation succeeded by the conventional inflation. We show the existence of inflationary attractors and obtain scaling solutions in the case of the exponential potential. Since all of the models agree with general relativity at late times, our results are also of use in classical theory where qualitative dynamics of some of the potentials has not been studied earlier.

We study the question of whether a helicity-transporting current is generated in a rotating photon gas at finite temperature. One problem is that there is no gauge-invariant local notion of helicity or helicity current. We circumvent this by studying not only the optical helicity current but also the gauge-invariant “zilch” current. In order to avoid problems of causality, we quantize the system on a cylinder of finite radius and then discuss the limit of infinite radius. We find that net helicity and zilch currents are only generated in the case of the finite radius and are due to duality-violating boundary conditions. A universal result exists for the current density on the axes of rotation in the high-temperature limit. To lowest order in the angular velocity, it takes a form similar to the well-known temperature dependence of the chiral vortical effect for chiral fermions. We briefly discuss possible relations to gravitational anomalies.

It has been suggested that dark matter is a superfluid of particles whose masses are on the rough order of ${10}^{-22}\mathrm{eV}$. Since the occupation numbers are huge, the state is coherent, and the speeds typical of orbital velocities in halos, it has generally been assumed that a classical effective nonrelativistic treatment is adequate. However, the Compton wavelength would be $\sim 1\mathrm{pc}$, and around the Compton scale concerns about some aspects of quantum measurement theory, known in principle but not quantitatively significant in previous cases, become pronounced. I estimate here the stress-energy operator, averaged over a few Compton wavelengths; a rough but useful approximation has a remarkably simple form. Conventional quantum measurement theory gives physically unacceptable results: a thought-experiment to measure the stress-energy is described which would involve only a modest apparatus but would excite particles in the observation volume to relativistic energies; these particles would escape the Galaxy, and there would be a substantial violation of energy conservation. Related foundational questions come up: the meaning of measurements of observables with continuous spectra, and the problem of predicting when measurements occur. The effective classical theory of fuzzy dark matter is not affected; however, the underlying quantum theory cannot be regarded as satisfactory without resolving these issues. But we may interpret the results more broadly. The macroscopic Compton scale amplifies inadequacies of measurement theory which have not previously seemed pressing.

A generic feature of scalar extensions of general relativity is the coupling of the scalar degrees of freedom to the trace $T$ of the energy-momentum tensor of matter fields. Interesting phenomenology arises when the trace becomes positive—when pressure exceeds one third of the energy density—a condition that may be satisfied in the core of neutron stars. In this work, we study how the positiveness of the trace of the energy-momentum tensor correlates with macroscopic properties of neutron stars. We first show that the compactness for which $T=0$ at the stellar center is approximately equation-of-state independent, and given by $C=0.262_{-0.017}^{+0.011}$ (90% confidence interval). Next, we exploit Bayesian inference to derive a probability distribution function for the value of $T$ at the stellar center given a putative measurement of the compactness of a neutron star. This investigation is a necessary step in order to use present and future observations of neutron star properties to constrain scalar-tensor theories based on effects that depend on the sign of $T$.

We consider extended covariant teleparallel $(f(T))$ gravity whose action is analytic in the torsion scalar and which is sourced by an $su(2)$ valued Yang-Mills field. Specifically, we search for regular solutions to the coupled $f(T)$-Yang-Mills system. For $f(T)=T$, not surprisingly, the Bartnik-McKinnon solitons of Einstein Yang-Mills theory are recovered. However, interesting effects are discovered with the addition of terms in the action which are nonlinear in the torsion scalar, which are specifically studied up to cubic order. With the addition of the nonlinear terms the number of regular solutions becomes finite. As well, beyond critical values of the coupling constants it is found that there exist no regular solutions. These behaviors are asymmetric with respect to the sign of the nonlinear coupling constants and the elimination of regular solutions turns out to be extremely sensitive to the presence of the cubic coupling. It may be possible, therefore, that with sufficiently high powers of torsion in the action, there may be no regular Yang-Mills static solutions.

We show that the monopole scalar charge of black holes in Einstein-Maxwell-dilaton theory is proportional to the electric potential at the event horizon, with a proportionality factor given by (minus) the scalar coupling constant. We also show that the scalar charge, in the weak electric charge limit, does not depend on the black hole spin. This result can be very useful to circumvent spin degeneracy issues when testing the theory against gravitational waves observations.

We discuss the freedom available in hybrid loop quantum cosmology to define canonical variables for the matter content and investigate whether this can be used to derive a quantum field theory with good properties for the matter sector. We study a primordial, inflationary, cosmological spacetime with inhomogeneous perturbations at lowest nontrivial order, and focus our attention on the contribution of minimally coupled fermionic perturbations of Dirac type. Within the framework of the hybrid quantization, we analyze the different possible separations of the homogeneous background and the inhomogeneous perturbations, by means of canonical transformations that mix the two separated sectors. These possibilities provide a family of sets of annihilation and creationlike fermionic variables, each of them with a different associated contribution to the total Hamiltonian. In all cases, imposing the quantum constraints and introducing a Born-Oppenheimer approximation, one can derive a Schrödinger equation for the fermionic part of the wave functions. The resulting evolution turns out to be generated, for each of the allowed choices of variables, by a version of the fermionic contribution to the Hamiltonian which is obtained by evaluating all the dependence on the homogeneous geometry at quantum expectation values. This equation contains a term that encodes the backreaction of the fermionic perturbations on the quantum dynamics of the homogeneous sector. We analyze this backreaction by solving the associated Heisenberg evolution of the fermionic annihilation and creation operators. Then, we identify the conditions that the choice of those operators must satisfy in order to lead to a finite backreaction. Finally, we discuss further restrictions on this choice so that the fermionic Hamiltonian that dictates the Schrödinger dynamics is densely defined in Fock space.

The secondary astrophysical production of $e^{+}$ and $\overline{p}$ cosmic rays is considered. Inclusive $\pi$-, $K$-, and $\overline{p}$-production cross sections in $pp$ collisions at large $\sqrt{s}$ are parametrized using recent experimental data at LHC energies. The astrophysical production-rate ratio $Q_{e^{+}}/Q_{\overline{p}}$ is calculated for an input cosmic ray proton flux consistent with local measurements. At $10<E<100\mathrm{GeV}$, the cosmic ray flux ratio $J_{e^{+}}/J_{\overline{p}}$ measured by AMS02 falls below the production-rate ratio by about 50%, while at high energy $E>100\mathrm{GeV}$, the measured flux ratio coincides with the production-rate ratio of the secondary source.

Various dark matter models predict annual and diurnal modulations of dark matter interaction rates in Earth-based experiments as a result of the Earth’s motion in the halo. Observation of such features can provide generic evidence for detection of dark matter interactions. This paper reports a search for both annual and diurnal rate modulations in the LUX dark matter experiment using over 20 calendar months of data acquired between 2013 and 2016. This search focuses on electron recoil events at low energies, where leptophilic dark matter interactions are expected to occur and where the DAMA experiment has observed a strong rate modulation for over two decades. By using the innermost volume of the LUX detector and developing robust cuts and corrections, we obtained a stable event rate of $2.3\pm 0.2\mathrm{cpd}/{\mathrm{keV}}_{\mathrm{ee}}/\mathrm{tonne}$, which is among the lowest in all dark matter experiments. No statistically significant annual modulation was observed in energy windows up to $26{\mathrm{keV}}_{\mathrm{ee}}$. Between 2 and $6{\mathrm{keV}}_{\mathrm{ee}}$, this analysis demonstrates the most sensitive annual modulation search up to date, with $9.2\sigma$ tension with the DAMA/LIBRA result. We also report no observation of diurnal modulations above $0.2\mathrm{cpd}/{\mathrm{keV}}_{\mathrm{ee}}/\mathrm{tonne}$ amplitude between 2 and $6{\mathrm{keV}}_{\mathrm{ee}}$.

The Georgi-Machacek (GM) model is a distinctive TeV-scale extension of the Standard Model (SM) due to the introduction of two (one real and one complex) scalar triplets to the Higgs sector. It predicts the existence of doubly charged Higgs bosons $H_5^{\pm \pm }$ and the vacuum expectation value of Higgs triplets $v_{\mathrm{\Delta }}$ can reach a few tens of GeV. In this paper, we perform a parameter scan of the GM model within the H5plane benchmark scenario and investigate in detail the single production of a doubly charged Higgs boson in association with a SM-like Higgs boson via vector-boson fusion at the 14 TeV LHC and 70 TeV Super Proton-Proton Collider. Both integrated cross section and differential distributions with respect to some kinematic variables for $pp\to W^{\pm }{W}^{\pm }\to H_5^{\pm \pm }{h}^0+2$ jets are provided up to the QCD next-to-leading order. In the signal-background analysis, we employ the madspin method to take into account the spin correlation and finite width effects of the intermediate Higgs and $W$ bosons and present some kinematic distributions of final leptons. The numerical results show that the SM background can be suppressed remarkably and the $H_5^{\pm \pm }{h}^0$ vector-boson fusion signal can be directly detected at future high-luminosity, high-energy hadron colliders by imposing a proper cut on the transverse mass $M_{T,{\ell }_1{\ell }_2}$.

We prove that the $SU(3{)}_C\otimes SU(2{)}_L\otimes SU(3{)}_R\otimes U(1{)}_X$ (3-2-3-1) gauge model always contains a matter parity $W_P=(-1{)}^{3(B-L)+2s}$ as conserved residual gauge symmetry, where $B-L=2(\beta T_{8R}+X)$ is a $SU(3{)}_R\otimes U(1{)}_X$ charge. Due to the non-Abelian nature of $B-L$, the $W$-odd and $W$-even fields are actually unified in gauge multiplets. We investigate two viable versions for dark matter according to $\beta =\pm 1/\sqrt{3}$, where the dark matter candidates can be fermion, scalar, or vector fields. We figure out the parameter spaces in the allowed regions of the relic density and direct detection cross sections. Additionally, we examine the neutrino masses induced by the seesaw mechanism along with associated lepton flavor violation processes. The new gauge boson searches at the LEPII and LHC are discussed.

We determine limits from SN 1987A on massive axionlike particles with masses in the 10 keV–100 MeV range and purely coupled to two photons. Axionlike particles produced in the core collapse escape from the star and decay into photons that can be observed as a delayed and diffuse burst. We discuss the time and angular distribution of such a signal. Looking into the future, we also estimate the possible improvements caused by better gamma-ray detectors or the explosion of the red supergiant Betelgeuse in a supernova event.