The tidal deformability of compact objects by a companion has a detectable imprint in the gravitational waves emitted by a binary system. This effect is governed by the so-called tidal Love numbers. For a particular theory of gravity, these depend solely on the object internal structure and they vanish for black holes in general relativity. A measurement compatible with nonzero tidal Love numbers could thus provide evidence of new physics in the strong-field regime. However, in realistic astrophysical scenarios, compact objects are surrounded by a nonvacuum environment. In this work, we study the tidal deformability of configurations of black holes immersed in matter, focusing on two analytical models representing an anisotropic fluid and a thin-shell of matter around a black hole. We then apply our results to the astrophysically relevant case of a black hole surrounded by an accretion disk, in the parameter region of interest of the upcoming LISA mission. Our results indicate that there are challenges to overcome concerning tests of strong-field gravity using tidal Love numbers.

If the inflationary phase lasted longer than the minimal period, the length scales observed today originated from modes that were smaller than the Planck length during inflation. It was recently argued that this “trans-Planckian problem” can never arise in a consistent string theory framework, which places a stringent constraint on the energy scale of inflation, $V^{1/4}\lesssim 10^9\mathrm{GeV}$. In this paper, we show that this requirement corresponds to a very small Hubble scale during inflation, $H_{\text{inf}}\lesssim 1\mathrm{GeV}$, and therefore has serious consequences on scenarios in which the dark matter density was generated by amplification of quantum fluctuations during inflation. We also present a class of inflationary models which both satisfy the above limit for the scale of inflation and are in perfect agreement with observational data.

Assuming that primordial black holes compose a fraction of dark matter, some of them may accumulate at the center of galaxy and perform a prograde or retrograde orbit against the gravity pointing towards the center exerted by the central massive black hole. If the mass of primordial black holes is of the order of stellar mass or smaller, such extreme mass ratio inspirals can emit gravitational waves and form a background due to incoherent superposition of all the contributions of the Universe. We investigate the stochastic gravitational-wave background energy density spectra from the directional source, the primordial black holes surrounding Sagittarius ${\mathrm{A}}^{*}$ of the Milky Way, and the isotropic extragalactic total contribution, respectively. As will be shown, the resultant stochastic gravitational-wave background energy density shows different spectrum features such as the peak positions in the frequency domain for the above two kinds of sources. Detection of stochastic gravitational-wave background with such a feature may provide evidence for the existence of primordial black holes. Conversely, a null searching result can put constraints on the abundance of primordial black holes in dark matter.

We elaborate the two-fold simplexlike structures of tree amplitudes in planar maximally supersymmetric Yang-Mills ($\mathcal{N}=4$ SYM), through its connection to a mathematical structure known as the positive Grassmannian. Exploiting the reduced Grassmannian geometry and the matrix form of on-shell recursion relation in terms of super momentum twistors, we manifest that tree amplitudes can be remarkably refined via the essential building blocks named as fully spanning cells. For a fixed number of negative helicities, an amplitude can be entirely captured by finite, compact information of the relevant fully spanning cells up to an arbitrarily large number of external particles.

We compute the symbol of the first two-loop amplitudes in planar $\mathcal{N}=4$ SYM with algebraic letters, the eight-point Next to Maximally Helicity Violating (NMHV) amplitude (or the dual octagon Wilson loops). We show how to apply $\overline{Q}$ equations of [S. Caron-Huot and S. He, J. High Energy Phys. 07 (2012) 174] for computing the differential of two-loop $n$-point NMHV amplitudes and present the result for $n=8$ explicitly. The symbol alphabet for octagon consists of 180 independent rational letters and 18 algebraic ones involving Gram-determinant square roots. We comment on all-loop predictions for final entries and aspects of the result valid for all multiplicities.

In the presence of an external magnetic field, the Carroll-Field-Jackiw term introduces a displacement current proportional to the Lorentz-violating background that induces a time-dependent magnetic field. Axionlike particles or hidden photons could generate an analogous signal, potentially detectable with the set-up suggested by Sikivie, Tanner and Sullivan—a sensitive magnetometer coupled to a superconducting LC circuit. We show that a similar setup, but with an externally driven pick-up loop whose area varies harmonically at $\sim \mathrm{Hz}$, can be used to probe the spatial components of the Lorentz-violating background to the level of $\lesssim {10}^{-31}\mathrm{GeV}$. This is eight orders of magnitude more sensitive than previous laboratory-based limits.

We provide the general expression of the cross section for exclusive deeply virtual photon electroproduction from a spin-$1/2$ target using current parametrizations of the off-forward correlation function in a nucleon for different beam and target polarization configurations up to twist-three accuracy. All contributions to the cross section including deeply virtual Compton scattering, the Bethe-Heitler process, and their interference, are described within a helicity-amplitude-based framework which is also relativistically covariant and readily applicable to both the laboratory frame and in a collider kinematic setting. Our formalism renders a clear physical interpretation of the various components of the cross section by making a connection with the known characteristic structure of the electron scattering coincidence reactions. In particular, we focus on the total angular momentum, $J_z$, and on the orbital angular momentum, $L_z$. On one side, we uncover an avenue to a precise extraction of $J_z$, given by the combination of generalized parton distributions, $H+E$, through a generalization of the Rosenbluth separation method used in elastic electron proton scattering. On the other side, we single out for the first time, the twist-three angular modulations of the cross section that are sensitive to $L_z$. The proposed generalized Rosenbluth technique adds constraints and can be extended to additional observables relevant to the mapping of the three-dimensional structure of the nucleon.

In this paper, we study the single longitudinal spin asymmetry $A_{UL}^{\sin ({\varphi }_h-{\varphi }_R)}$ of dihadron production in semi-inclusive deep inelastic scattering (SIDIS) via helicity-dependent dihadron fragmentation function (DiFF), which describes the correlation of the longitudinal polarization of a fragmenting quark with the transverse momenta of the produced hadron pair. Recently, experimental searching for this azimuthal asymmetry in dihadron SIDIS by the COMPASS Collaboration yielded a very small signal. Here we calculate this unknown T-odd DiFF $G_1^{\perp }$ using a spectator model to access the asymmetry and clarify why the signal is very small. The transverse momentum dependent factorization method, in which the transverse momentum of the final state hadron pair leaves unintegrated, has been applied. We estimate the $\sin ({\varphi }_h-{\varphi }_R)$ asymmetry at the kinematics of COMPASS experiments and compare with the data. What’s more, the predictions on the same asymmetry are also made at the electron ion collider.

We systematically calculate the isospin violating decay, $D_s^{*}\to D_s{\pi }^0$, with heavy meson chiral perturbation theory up to $\mathcal{O}(p^3)$ including the loop diagrams. The $\mathcal{O}(p^3)$ tree-level amplitudes contain four undetermined low energy constants. We use two strategies to estimate them. Using the nonanalytic dominance approximation, we get $\mathrm{\Gamma }[D_s^{*}\to D_s{\pi }^0]=8.1_{-2.6}^{+3.0}\mathrm{eV}$. Using the naturalness assumption, we obtain the range of the isospin violating decay width as [5.2, 11.7] eV. These two strategies give similar sizes. We find that the contribution of the $\mathcal{O}(p^3)$ corrections might be significant.

Pentaquark states have been extensively investigated theoretically in the context of the constituent quark model. In this paper results of an experimental search for pentaquarks in the ${\mathrm{\Xi }}^{-}$ ${\pi }^{-}$, ${\mathrm{\Xi }}^{-}$ ${\pi }^{+}$, ${\overline{\mathrm{\Xi }}}^{+}$ ${\pi }^{-}$ and ${\overline{\mathrm{\Xi }}}^{+}$ ${\pi }^{+}$ invariant mass spectra in proton-proton interactions at $\sqrt{s}=17.3\mathrm{GeV}$ are presented. Previous possible evidence from the NA49 collaboration of the existence of a narrow ${\mathrm{\Xi }}^{-}$ ${\pi }^{-}$ baryon resonance in $\mathrm{p}+\mathrm{p}$ interactions is not confirmed with almost 10 times greater event statistics. The search was performed using the NA61/SHINE detector which reuses the main components of the NA49 apparatus. No signal was observed with either the selection cuts of NA49 or newly optimized cuts.

We study the portion of an asymptotically Anti–de Sitter geometry’s bulk where the metric can be reconstructed, given the areas of minimal two-surfaces anchored to a fixed boundary subregion. We exhibit situations in which this region can reach parametrically far outside of the entanglement wedge. If the setting is furthermore holographic, so that the bulk geometry is dual to a state in a conformal field theory (CFT), these minimal two-surface areas can be deduced from the expectation values of operators localized within the boundary subregion. This presents us with an alternative: either the reduced CFT state encodes significant information about the bulk beyond the entanglement wedge, challenging conventional intuition about holographic subregion duality, or the reduced CFT state fails to contain information about operators whose expectation values give the areas of minimal two-surfaces anchored within that subregion, challenging conventional intuition about the holographic dictionary.

We investigate the relationship between asymptotic symmetries of QCD and vacuum transitions induced during scattering. Starting with the Fock vacuum in the far past, the infinity of conservation laws associated to (non-Abelian) asymptotic symmetries in QCD can be used to determine the vacuum in the far future. We show that the corresponding asymptotic Hilbert space in the future is generated by a class of dressed states in which each finite energy particle is dressed by a cloud of interacting soft gluons. We identify the precise structure of the dressing using conservation laws and show that the corresponding asymptotic states are equivalent to the generalized coherent states defined by Catani et al.

We study the compactification of the six-dimensional (6D) $\mathcal{N}=(2,0)$ superconformal field theory on the product of a Riemann surface with flux and a circle. On the one hand, this can be understood by first reducing on the Riemann surface, giving rise to 4D $\mathcal{N}=1$ and $\mathcal{N}=2$ class $\mathcal{S}$ theories, which we then reduce on $S^1$ to get 3D $\mathcal{N}=2$ and $\mathcal{N}=4$ class $\mathcal{S}$ theories. On the other hand, we may first compactify on $S^1$ to get the 5D $\mathcal{N}=2$ Yang-Mills theory. By studying its reduction on a Riemann surface, we obtain a mirror dual description of 3D class $\mathcal{S}$ theories, generalizing the star-shaped quiver theories of Benini, Tachikawa, and Xie. We comment on some global properties of the gauge group in these reductions and test the dualities by computing various supersymmetric partition functions.

The Teukolsky master equation—a fundamental equation for test fields of any spin, or perturbations, in type D spacetimes—is classically treated in its separated form. Then the solutions representing even the simplest sources—point particles—are expressed in terms of series. The only known exception is a static particle (charge or mass) in the vicinity of a Schwarzschild black hole. Here, we present a generalization of this result to a static point particle of arbitrary spin at the axis of a Kerr black hole. A simple algebraic formula for the Debye potential from which all the Newman–Penrose components of the field under consideration can be generated is written down explicitly. Later, we focus on the electromagnetic field and employ the classic Appell’s trick (moving the source into a complex space) to get the so-called electromagnetic magic field on the Kerr background. Thus the field of nontrivial extended yet spatially bounded source is obtained. We also show that a static electric point charge above the Kerr black hole induces, except for an expected electric monopole, also a magnetic monopole charge on the black hole itself. This contribution has to be compensated. On a general level we discuss Teukolsky–Starobinsky identities in terms of the Debye potentials.

We extend the Ori and Thorne (OT) procedure to compute the transition from an adiabatic inspiral into a geodesic plunge for any spin, with emphasis on near-extremal ones. Our analysis revisits the validity of the approximations made in OT. In particular, we discuss possible effects coming from eccentricity and nongeodesic past-history of the orbital evolution. We find three different scaling regimes according to whether the mass ratio is much smaller, of the same order or much larger than the near extremal parameter describing how fast the primary black hole rotates. Eccentricity and nongeodesic past-history corrections are always subleading, indicating that the quasicircular approximation applies throughout the transition regime. However, we show that the OT assumption that the energy and angular momentum evolve linearly with proper time must be modified in the near-extremal regime. Using our transition equations, we describe an algorithm to compute the full worldline in proper time for an extreme mass ratio inspiral (EMRI) and the resultant gravitational waveform in the high spin limit.

We consider a modified Brans-Dicke theory in which, instead of the usual Brans-Dicke parameter, a new dimensionful parameter appears that modifies the kinetic term of the scalar field coupled to gravity. Solving the coupled Einstein-Klein-Gordon equations we find new spherically symmetric solutions. Depending on the choices of the parameters these solutions reduce to the Schwarzschild solution of general relativity, and they give new wormhole solutions that depend on the new parameter.

Conformal symmetries appear in many parts of physics and play a unique role in exploring the Universe. We consider the possibility of constructing conformal theories of gravity in the symmetric teleparallel gravity framework, where gravitation is expressed through nonmetricity rather than curvature or torsion. We demonstrate that it is possible to formulate a family of conformal theories with second-order field equations and have the metric tensor as the fundamental variable. Moreover, we consider the addition of a scalar field to the theory, and compare the results to the teleparallel gravity setting. Finally, we present the scalar-tensor representation of modified symmetric teleparallel theories, and among others we show that there is an interesting subcase that has the possibility of playing the role of dark energy.

In this work, we study the evolution of a spatially flat Universe by considering a viscous dark matter and perfect fluids for dark energy and radiation, including an interaction term between dark matter and dark energy. In the first part, we analyze the general properties of the Universe by performing a stability analysis, and then we constrain the free parameters of the model using the latest and cosmological-independent measurements of the Hubble parameter. We find consistency between the viscosity coefficient and the condition imposed by the second law of the thermodynamics. The second part is dedicated to constraining the free parameter of the interacting viscous model (IVM) for three particular cases: the viscous model (VM), interacting model (IM), and the perfect fluid case [Lambda-Cold Dark Matter (LCDM)]. We report the deceleration parameters as $q_0=-0.54_{-0.05}^{+0.06}$, $-0.58_{-0.04}^{+0.05}$, $-0.58_{-0.05}^{+0.05}$, and $-0.63_{-0.02}^{+0.02}$, together with the jerk parameters as $j_0=0.87_{-0.09}^{+0.06}$, ${0.94}_{-0.06}^{+0.04}$, ${0.91}_{-0.10}^{+0.06}$, and 1.0 for the IVM, VM, IM, and LCDM respectively, where the uncertainties correspond at 68% confidence level. It is worth mentioning that all the particular cases are in good agreement with LCDM, in some cases producing even better fits, with the advantage of eliminating some problems that afflict the standard cosmological model.

In this work, we propose a powerful probe of neutrino effects on the large-scale structure (LSS) of the Universe, i.e., Minkowski functionals (MFs). The morphology of LSS can be fully described by four MFs. This tool, with strong statistical power, is robust to various systematics and can comprehensively probe all orders of N-point statistics. By using a pair of high-resolution N-body simulations, for the first time, we comprehensively studied the subtle neutrino effects on the morphology of LSS. For an ideal LSS survey of volume $\sim 1.73{\mathrm{Gpc}}^3/h^3$, neutrino signals are mainly detected from void regions with a significant level up to $\sim 10\sigma$ and $\sim 300\sigma$ for CDM and total matter density fields, respectively. This demonstrates its enormous potential for much improving the neutrino mass constraint in the data analysis of upcoming ambitious LSS surveys.