Light bending is one of the significant predictions of general relativity (GR) and it has been confirmed with great accuracy during the past one hundred years. In this paper, we semiclassically calculate the deflection angle for the photons that just graze the Sun in the infinite derivative theories of gravity (IDG) which is a ghost and singularity free theory of gravity. From our calculations, we find that the deflection angle $\theta$ only depends on $\mathrm{\Lambda }/E$. $\theta \to {\theta }_E$ when $\mathrm{\Lambda }/E\to \infty$ and decrease to zero when $\mathrm{\Lambda }/E\to 0$. The transition interval occurs at $10^4<E/\mathrm{\Lambda }<10^7$. It should be pointed out that this model can be tested by the Chandra X-ray Observatory if $0.01\mathrm{eV}<\mathrm{\Lambda }<0.1\mathrm{eV}$.

We show that in $D=2n+1$ dimensions, when mass is negative and all angular momenta are nonvanishing, Kerr and Kerr-anti–de Sitter (AdS) metrics describe smooth time machines, with no curvature singularity. Turning off the angular momenta appropriately can lead to static AdS solitons with negative mass. Setting zero the cosmological constant yields a class of Ricci-flat Kähler metrics in $D=2n$ dimensions. We also show that Euclidean-signatured AdS solitons with negative mass can also arise in odd dimensions. We then construct time machines in $D=5$ minimal gauged supergravity that carry only magnetic dipole charges. Turning off the cosmological constant, the time machine becomes massless and asymptotically flat. It can be described as a constant time bundle over the Eguchi-Hanson instanton.

Usual gauge fixing procedures in classical general relativity rely on the existence of solutions of a second order wave equation. We propose to use these equations to relate asymptotic symmetries at infinity to asymptotic symmetries of a black hole horizon, in tune with recent proposals. We illustrate the construction for the Bañados-Teitelboim-Zanelli (BTZ) and four-dimensional Kerr black holes. We find in both cases a realization of the group of diffeomorphisms of the real line.

By assuming the kinetic coupling $f^2(\varphi )FF$ of the effective inflaton field $\varphi$ with the electromagnetic field, we explore magnetogenesis during the inflation and preheating stages in the $R^2$ Starobinsky model. We consider the case of the exponential coupling function $f(\varphi )=\exp (\alpha \varphi /M_p)$ and show that for $\alpha \sim 12–15$ it is possible to generate the large-scale magnetic fields with strength $\gtrsim {10}^{-15}$ Gauss at the present epoch. The spectrum of generated magnetic fields is blue with the spectral index $n=1+s$, $s>0$. We have found that for the relevant values of the coupling parameter, $\alpha =12–15$, the model avoids the backreaction problem for all relevant modes.

Constraints on primordial black holes in the range ${10}^{-18}{M}_{\odot }$ to $10^3{M}_{\odot }$ are reevaluated for a general class of extended mass functions. Whereas previous work has assumed that PBHs are produced with one single mass, instead there is expected to be a range of masses even in the case of production from a single mechanism; constraints therefore change from previous literature. Although tightly constrained in the majority of cases, it is shown that, even under conservative assumptions, primordial black holes in the mass range ${10}^{-10}{M}_{\odot }$ to ${10}^{-8}{M}_{\odot }$ could still constitute the entirety of the dark matter. This stresses both the importance for a comprehensive reevaluation of all respective constraints that have previously been evaluated only for a monochromatic mass function and the need to obtain more constraints in the allowed mass range.

There is a wide consensus on the correct dynamics of the background in loop quantum cosmology. In this article we make a systematic investigation of the duration of inflation by varying what we think to be the most important “unknowns” of the model: the way to set initial conditions, the amount of shear at the bounce and the shape of the inflaton potential.

We compute the longitudinal electrical conductivity in the presence of a strong background magnetic field in complete leading order of perturbative QCD, based on the assumed hierarchy of scales ${\alpha }_{s}eB\ll (m_q^2,T^2)\ll eB$. We formulate an effective kinetic theory of lowest Landau level quarks with the leading order QCD collision term arising from 1-to-2 processes that become possible due to $1+1$ dimensional Landau level kinematics. In the small $m_q/T\ll 1$ regime, the longitudinal conductivity behaves as ${\sigma }_{zz}\sim e^2(eB)T/({\alpha }_s{m}_q^2\log (T/m_q))$, where the quark mass dependence can be understood from the chiral anomaly with the axial charge relaxation provided by a finite quark mass $m_q$. We also present parametric estimates for the longitudinal and transverse “color conductivities” in the presence of the strong magnetic field, by computing dominant damping rates for quarks and gluons that are responsible for color charge transportation. We observe that the longitudinal color conductivity is enhanced by the strong magnetic field, which implies that the sphaleron transition rate in perturbative QCD is suppressed by the strong magnetic field due to the enhanced Lenz’s law in color field dynamics.

We explore the dependence of fermion propagators on the covariant gauge fixing parameter in quantum electrodynamics (QED) with the number of spacetime dimensions kept explicit. Gauge covariance is controlled by the Landau-Khalatnikov-Fradkin transformation (LKFT). Utilizing its group nature, the LKFT for a fermion propagator in Minkowski space is solved exactly. The special scenario of 3D is used to test claims made for general cases. When renormalized correctly, a simplification of the LKFT in 4D has been achieved with the help of fractional calculus.

We consider a minimal renormalizable and gauge invariant dark matter (DM) model, in which the singlet fermion DM has only axial couplings to a new pseudoscalar mediator. The mixing between the pseudoscalar mediator and the standard model (SM) Higgs boson induces the interactions between the DM and SM particles. The DM candidate in this model can provide the correct thermal relic density and evades all direct detections, while it can produce observable signals in indirect detection experiments due to its large annihilation cross section. A comparative study for DM phenomenology at the LHC is conducted for models with scalar mediators that have either scalar or pseudoscalar couplings to SM particles and the DM. We find that the three scenarios have distinguishable features in scalar decay branching ratio, DM pair production cross section as well as the signal reaches at the LHC. The LHC searches for some visible signals related to the scalar sector are also discussed.

In the early stages of heavy-ion collisions, the hot QCD matter expands more longitudinally than transversely. This imbalance causes the system to become rapidly colder in the longitudinal direction, and a local momentum anisotropy appears. In this paper, we study the heavy-quarkonium spectrum in the presence of a small plasma anisotropy. We work in the framework of potential nonrelativistic QCD at finite temperature. We inspect arrangements of nonrelativistic and thermal scales complementary to those considered in the literature. In particular, we consider temperatures larger and Debye masses smaller than the binding energy, which is a temperature range relevant for presently running LHC experiments. In this setting, we compute the leading thermal corrections to the binding energy and the thermal width induced by quarkonium gluodissociation.

The CLAS collaboration recently reported measured ratios of pion and kaon electroproduction cross sections from a proton target and extracted the ratios for light and strange quark-antiquark pairs, $u\overline{u}/d\overline{d}$ and $s\overline{s}/d\overline{d}$. Within an extended chiral constituent quark formalism, we investigate contributions to those ratios from the nonperturbative mechanism due to all possible intrinsic $|uudQ\overline{Q}⟩$ Fock states in the proton; with $Q\overline{Q}\equiv u\overline{u},d\overline{d},s\overline{s},c\overline{c}$. Our results are compared with the CLAS data and findings from other phenomenological approaches, offering insights into the manifestations of the genuine five-quark Fock states in the proton and its relevance to interpreting the experimental data.

The $\gamma {\gamma }^{*}\to {\eta }_{c,b}$ transition form factors are computed using a continuum approach to the two valence-body bound-state problem in relativistic quantum field theory, and thereby unified with equivalent calculations of electromagnetic pion elastic and transition form factors. The resulting $\gamma {\gamma }^{*}\to {\eta }_c$ form factor, $G_{{\eta }_c}(Q^2)$, is consistent with available data; significantly, at accessible momentum transfers, $Q^2{G}_{{\eta }_c}(Q^2)$ lies well below its conformal limit. These observations confirm that the leading-twist parton distribution amplitudes of heavy-heavy bound states are compressed relative to the conformal limit. A clear understanding of the distribution of valence quarks within mesons thus emerges, a picture which connects Goldstone modes, built from the lightest quarks in nature, with systems containing the heaviest valence quarks that can now be studied experimentally, and highlights basic facts about manifestations of mass within the Standard Model.

A previous formal derivation of the effective chiral Lagrangian for low-lying pseudoscalar mesons from first-principles QCD without approximations [Q. Wang, Y.-P. Kuang, X.-L. Wang, and M. Xiao, Phys. Rev. D 61, 054011 (2000)] is generalized to further include scalar, vector, and axial-vector mesons. In the large $N_c$ limit and with an Abelian approximation, we show that the properties of the newly added mesons in our formalism are determined by the corresponding underlying fundamental homogeneous Bethe-Salpeter equation in the ladder approximation, which yields the equations of motion for the scalar, vector, and axial-vector meson fields at the level of an effective chiral Lagrangian. The masses appearing in the equations of motion of the meson fields are those determined by the corresponding Bethe-Salpeter equation.

In this article, we present our global QCD analysis of leading neutron production in deep inelastic scattering at H1 and ZEUS collaborations. The analysis is performed in the framework of a perturbative QCD description for semi-inclusive processes, which is based on the fracture functions approach. Modeling the nonperturbative part of the fragmentation process at the input scale ${\mathrm{Q}}_0^2$, we analyze the ${\mathrm{Q}}^2$ dependence of the leading neutron structure functions and obtain the neutron fracture functions (neutron FFs) from next-to-leading order global QCD fit to data. We have also performed a careful estimation of the uncertainties using the “Hessian method” for the neutron FFs and corresponding observables originating from experimental errors. The predictions based on the obtained neutron FFs are in good agreement with all data analyzed, at small and large longitudinal momentum fraction $x_L$ as well as the scaled fractional momentum variable $\beta$.

The effects of fluctuations are discussed around the phase boundary of the inhomogeneous chiral transition between the inhomogeneous chiral phase and the chiral-restored phase within the two-flavor Nambu–Jona-Lasinio model in the chiral limit. The particular roles of thermal and quantum fluctuations are elucidated and a continuity of their effects across the phase boundary is suggested. In addition, it is argued that anomalies in the thermodynamic quantities should have phenomenological implications for the inhomogeneous chiral transition. Some common features for other phase transitions, such as those from the normal to the inhomogeneous Fulde-Ferrell-Larkin-Ovchinnikov state in superconductivity, are also emphasized.

We consider the exclusive $P_{\ell 4}$ decays, $P\to (P_1{P}_2{)}_V\ell {\nu }_{\ell }$, where the subindex $V$ means that the invariant mass of the pseudoscalar pair is taken within a small window around the mass of the vector meson $V$. Pole contributions beyond the dominant $P\to V(\to P_1{P}_2)\ell {\nu }_{\ell }$ amplitude of $P_{\ell 4}$ decays are identified, which, in turn, affect the determination of the CKM matrix elements $|V_{q{q}^{\prime }}|$. We evaluate the effects of those contributions in the extraction of bottom and charm quark mixings. An application to $B\to (\pi \pi {)}_{\rho }\ell {\nu }_{\ell }$ data from the Belle Collaboration shows an increase in the extracted value of $|V_{ub}|$ in better agreement with determinations based on $B\to \pi \ell {\nu }_{\ell }$ decays. The effect of the $\rho$ and $D^{*}$ pole contributions in the determination of $|V_{cd}|$ from the decay $D\to \pi \pi {\ell }^{-}{\overline{\nu }}_{\ell }$ has also been investigated.

We study the processes $e^{+}{e}^{-}\to {\gamma }_{\mathrm{ISR}}J/\psi$, where $J/\psi \to {\pi }^{+}{\pi }^{-}{\pi }^0$, $J/\psi \to K^{+}{K}^{-}{\pi }^0$, and $J/\psi \to K_S^0{K}^{\pm }{\pi }^{\mp }$ using a data sample of $519{\mathrm{fb}}^{-1}$ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at center-of-mass energies at and near the $\mathrm{{\rm Y}}(nS)$ ($n=2,3,4$) resonances. We measure the ratio of branching fractions ${\mathcal{R}}_1=\frac{\mathcal{B}(J/\psi \to K^{+}{K}^{-}{\pi }^0)}{\mathcal{B}(J/\psi \to {\pi }^{+}{\pi }^{-}{\pi }^0)}$ and ${\mathcal{R}}_2=\frac{\mathcal{B}(J/\psi \to K_S^0{K}^{\pm }{\pi }^{\mp })}{\mathcal{B}(J/\psi \to {\pi }^{+}{\pi }^{-}{\pi }^0)}$. We perform Dalitz plot analyses of the three $J/\psi$ decay modes and measure fractions for resonances contributing to the decays. We also analyze the $J/\psi \to {\pi }^{+}{\pi }^{-}{\pi }^0$ decay using the Veneziano model. We observe structures compatible with the presence of $\rho (1450)$ in all three $J/\psi$ decay modes and measure the relative branching fraction: $\mathcal{R}(\rho (1450))=\frac{\mathcal{B}(\rho (1450)\to K^{+}{K}^{-})}{\mathcal{B}(\rho (1450)\to {\pi }^{+}{\pi }^{-})}=0.307\pm 0.084(\text{stat})\pm 0.082(\text{sys})$.

We present a new calculation of the mass and width of the exotic $0^{--}$ glueball in the framework of the QCD sum rules. We next construct a new current which couples to a pure $0^{--}$ gluon state and derive consistent and stable sum rules. A previously used current in this approach was shown to be inconsistent. We obtain for this state a mass $M_G=6.3_{-1.1}^{+0.8}\mathrm{GeV}$ and an upper limit for the total width ${\mathrm{\Gamma }}_G\le 235\mathrm{MeV}$. These values can be used as an important guide for the experimental search of this exotic state. We argue that the mixing of this glueball state with the $0^{--}$ tetraquark is very small. Therefore, the exotic $0^{--}$ glueball can be considered as a pure gluon state.

We use holography to compute spectral functions of certain fermionic operators in three different finite-density, zero-temperature states of Aharony-Bergman-Jafferis-Maldacena (ABJM) theory with a broken $U(1)$ symmetry. In each of the three states, dual to previously studied domain wall solutions of four-dimensional gauged supergravity, we find that the fermionic operators have gapped spectra. In one case the gap can be traced to the small charge of the fermions, while in the other cases it is due to a particular interaction that mixes particles and holes.