In flat spacetime, the vacuum neutrino flavor oscillations are known to be sensitive only to the difference between the squared masses, and not to the individual masses, of neutrinos. In this work, we show that the lensing of neutrinos induced by a gravitational source substantially modifies this standard picture and it gives rise to a novel contribution through which the oscillation probabilities also depend on the individual neutrino masses. A gravitating mass located between a source and a detector deflects the neutrinos in their journey, and at a detection point, neutrinos arriving through different paths can lead to the phenomenon of interference. The flavor transition probabilities computed in the presence of such interference depend on the individual masses of neutrinos whenever there is a nonzero path difference between the interfering neutrinos. We demonstrate this explicitly by considering an example of weak lensing induced by a Schwarzschild mass. Through the simplest two flavor case, we show that the oscillation probability in the presence of lensing is sensitive to the sign of $\mathrm{\Delta }{m}^2=m_2^2-m_1^2$, for nonmaximal mixing between two neutrinos, unlike in the case of standard vacuum oscillation in flat spacetime. Further, the probability itself oscillates with respect to the path difference and the frequency of such oscillations depends on the absolute mass scale $m_1$ or $m_2$. We also give results for realistic three flavor case and discuss various implications of gravitationally modified neutrino oscillations and means of observing them.

We present a new family of topological charged hairy black hole solutions in asymptotically anti–de Sitter (AdS) space in $D$ dimensions. We solve the coupled Einstein-Maxwell-scalar gravity system and obtain exact charged hairy black hole solutions with planar, spherical, and hyperbolic horizon topologies. The scalar field is regular everywhere. We discuss the thermodynamics of the hairy black hole and find drastic changes in its thermodynamic structure due to the scalar field. For the case of planar and spherical horizons, we find charged hairy/Reissner-Nordstrom (RN)-AdS black hole phase transition, with thermodynamically preferred and stable charged hairy phases at low temperature. For the case of hyperbolic horizon, no such transition occurs and RN-AdS black holes are always thermodynamically favored.

Extreme-mass-ratio inspirals (EMRIs) detectable by the future Laser Interferometer Space Antenna provide a unique way to test general relativity and fundamental physics. Motivated by this possibility, here we study in detail the EMRI dynamics in the presence of a spinning secondary, collecting and extending various results that appeared in previous work and also providing useful intermediate steps and new relations for the first time. We present the results of a frequency-domain code that computes gravitational-wave fluxes and the adiabatic orbital evolution for the case of circular, equatorial orbits with (anti)aligned spins. The spin of the secondary starts to affect the gravitational-wave phase at the first post-adiabatic order (as does the first-order conservative self-force) and introduces a detectable dephasing, which can be used to measure it at the 5–25% level, depending on individual spins. In a companion paper we discuss the implication of this effect for tests of the Kerr bound.

We explore different gauge choices in the moving puncture formulation in order to improve the accuracy of a linear momentum measure evaluated on the horizon of the remnant black hole produced by the merger of a binary. In particular, motivated by the study of gauges in which $m\eta$ takes on a constant value, we design a gauge via a variable shift parameter $m\eta (\overrightarrow{r}(t))$. This new parameter takes a low value asymptotically, as well as at the locations of the orbiting punctures, and then takes on a value of approximately 2 at the final hole horizon. This choice then follows the remnant black hole as it moves due to its net recoil velocity. We find that this choice keeps the accuracy of the binary evolution. Furthermore, if the asymptotic value of the parameter $m\eta$ is chosen about or below 1.0, it produces more accurate results for the recoil velocity than the corresponding evaluation of the radiated linear momentum at infinity, for typical numerical resolutions. Detailed studies of an unequal mass $q=m_1/m_2=1/3$ nonspinning binary are provided and then verified for other mass ratios $(q=1/2,1/5)$ and spinning ($q=1$) binary black hole mergers.

We investigate the cosmological applications of Myrzakulov $F(R,T)$ gravity. In this theory ones uses a specific but nonspecial connection, and thus both curvature and torsion are dynamical fields related to gravity. We introduce a parametrization that quantifies the deviation of curvature and torsion scalars form their corresponding values obtained using the special Levi-Civita and Weitzenböck connections, and we extract the cosmological field equations following the minisuperspace procedure. Even for the simple case where the action of the theory is linear in $R$ and $T$, we find that the Friedmann equations contain new terms of geometrical origin, reflecting the nonspecial connection. Applying the theory at late times we find that we can acquire the thermal history of the universe, where dark energy can be quintessencelike or phantomlike, or behave exactly as a cosmological constant and thus reproducing $\mathrm{\Lambda }\mathrm{CDM}$ cosmology. Furthermore, we show that these features are obtained for other Lagrangian choices, too. Finally, early-time application leads to the de Sitter solution, as well as to an inflationary realization with the desired scale-factor evolution.

The aim of this article is to understand the role of dust reference fields, often also called clocks, on cosmological perturbations around a classical spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) universe. We derive the Mukhanov-Sasaki equation for the Brown-Kuchař and Gaussian dust models, which both consider four dust fields as reference fields. The reduced phase space of Dirac observables, that is the gauge-invariant part of the theory, is constructed by means of an observable map applied to all elementary phase space variables of the coupled system, consisting of gravity, a massive scalar field and the dust degrees of freedom and automatically yields the set of independent physical variables. The evolution of these observables is governed by a so called physical Hamiltonian which can be derived once the set of reference fields are chosen and differs for each model. First, the reduced phase space for full general relativity as well as the corresponding equations of motion are derived for full general relativity. Then from this, the gauge-invariant versions of the equations of motion for the background are derived which contain a fingerprint of the dust reference fields. Afterwards we study linear cosmological perturbations around a FLRW metric using the scalar-vector-tensor decomposition and derive the equation of motion for the Mukhanov-Sasaki variable in this formalism for a chosen set of variables on the reduced phase space and expressed in terms of Dirac observables. The Mukhanov-Sasaki equation involves additional contributions that can be understood as back reactions from the dust reference fields. These additional dust contributions to the Mukhanov-Sasaki equation were absent if the dust energy and momentum density as well as their perturbations are vanishing. The nature of the correction terms suggests that Brown-Kuchař and Gaussian dust reference fields contribute differently. We numerically study the behavior of the dust contributions to the Mukhanov-Sasaki equation during inflation.

Discrepant measurements of the Universe’s expansion rate ($H_0$) may signal physics beyond the standard cosmological model. Here I describe two early modified gravity mechanisms that reconcile $H_0$ value by increasing the expansion rate in the era of matter-radiation equality. These mechanisms, based on viable Horndeski theories, require significantly less fine-tuned initial conditions than early dark energy with oscillating scalar fields. In imperfect dark energy at equality (IDEE), the initial energy density dilutes slower than radiation but faster than matter, naturally peaking around the era of equality. The minimal IDEE model, a cubic Galileon, is too constrained by the cosmic microwave background (Planck) and baryon acoustic oscillations (BAO) to relieve the $H_0$ tension. In enhanced early gravity (EEG), the scalar field value modulates the cosmological strength of gravity. The minimal EEG model, an exponentially coupled cubic Galileon, gives a $\mathrm{Planck}+\mathrm{BAO}$ value $H_0=68.7\pm 1.5$ (68% CL), reducing the tension with SH0ES from $4.4\sigma$ to $2.6\sigma$. Additionally, Galileon contributions to cosmic acceleration may reconcile $H_0$ via late-universe phantom expansion (LUPE). Combining LUPE, EEG and $\mathrm{\Lambda }$ reduces the tension between Planck, BAO, and SH0ES to $2.5\sigma$. I will also describe additional tests of coupled Galileons based on local gravity tests, primordial element abundances and gravitational waves. While further model building is required to fully resolve the $H_0$ problem and satisfy all available observations, these examples show the wealth of possibilities to solve cosmological tensions beyond Einstein’s general relativity.

We study the dynamics of merging compact binaries near a rotating supermassive black hole (SMBH) in a hierarchical triple configuration. We include various general relativistic effects that couple the inner orbit, the outer orbit and the spin of the SMBH. During the orbital decay due to gravitational radiation, the inner binary can encounter an “apsidal precession resonance” and experience eccentricity excitation. This resonance occurs when the apsidal precession rate of the inner binary matches that of the outer binary, with the precessions driven by both Newtonian interactions and various post-Newtonian effects. The eccentricity excitation requires the outer orbit to have a finite eccentricity, and is most effective for triples with small mutual inclinations, in contrast to the well-studied Lidov-Kozai effect. The resonance and the associated eccentricity growth may occur while the binary emits gravitational waves in the low-frequency band, and may be detectable by future space-based gravitational wave detectors.

The Skyrme model and its generalizations provide a conceptually appealing field-theory basis for the description of nuclear matter and, after its coupling to gravity, also of neutron stars. In particular, a specific Skyrme submodel, the so-called Bogomol’nyi-Prasad-Sommerfield (BPS) Skyrme model, allows for both an exact field-theoretic and a mean-field treatment of neutron stars, as a consequence of its perfect fluid property. A pure BPS Skyrme model description of neutron stars, however, only describes the neutron star core, by construction. Here we consider different possibilities to extrapolate a BPS Skyrme neutron star at high baryon density to a description valid at lower densities. In the exact field-theoretic case, a simple effective description of the neutron star crust can be used, because the exact BPS Skyrme neutron star solutions formally extend to sufficiently low densities. In the mean-field case, on the other hand, the BPS Skyrme neutron star solutions always remain above the nuclear saturation density and, therefore, must be joined to a different nuclear physics equation of state already for the outer core. We study the resulting neutron stars in both cases, facilitating an even more complete comparison between skyrmionic neutron stars and neutron stars obtained from other approaches, as well as with observations.

Neutrino decay modifies neutrino propagation in a unique way; not only is there flavor changing as there is in neutrino oscillations, there is also energy transport from initial to final neutrinos. The most sensitive direct probe of neutrino decay is currently IceCube which can measure the energy and flavor of neutrinos traveling over extragalactic distances. For the first time, we calculate the flavor transition probability for the cases of visible and invisible neutrino decay, including the effects of the expansion of the Universe, and consider the implications for IceCube. As an example, we demonstrate how neutrino decay addresses a tension in the IceCube data.

We obtain the electromagnetic form factors, the axial form factor, and the parton distribution functions of the proton from the eigenstates of a light-front effective Hamiltonian in the leading Fock representation suitable for low-momentum scale applications. The electromagnetic and the axial form factors are found to be in agreement with the available experimental data. The unpolarized, the helicity, and the transversity valence quark distributions, after QCD evolution, are consistent with the global QCD analyses. The tensor charge also agrees the experimental data, while the axial charge is somewhat outside the experimental error bar.

For low-mass (frequency $\ll \mathrm{GHz}$) axions, dark matter detection experiments searching for an axion-photon-photon coupling generally have suppressed sensitivity, if they use a static background magnetic field. This geometric suppression can be alleviated by using a high-frequency oscillating background field. Here, we present a high-level sketch of such an experiment, using superconducting cavities at $\sim \mathrm{GHz}$ frequencies. We discuss the physical limits on signal power arising from cavity properties, and point out cavity geometries that could circumvent some of these limitations. We also consider how backgrounds, including vibrational noise and drive signal leakage, might impact sensitivity. While practical microwave field strengths are significantly below attainable static magnetic fields, the lack of geometric suppression, and higher quality factors, may allow superconducting cavity experiments to be competitive in some regimes.

We study a dark matter (DM) model in which the dominant coupling to the standard model occurs through a neutrino-DM-scalar coupling. The new singlet scalar will generically have couplings to nuclei/electrons arising from renormalizable Higgs portal interactions. As a result, the DM particle $X$ can convert into a neutrino via scattering on a target nucleus $\mathcal{N}$: $X+\mathcal{N}\to \nu +\mathcal{N}$, leading to striking signatures at direct detection experiments. Similarly, DM can be produced in neutrino scattering events at neutrino experiments: $\nu +\mathcal{N}\to X+\mathcal{N}$, predicting spectral distortions at experiments such as COHERENT. Furthermore, the model allows for late kinetic decoupling of dark matter with implications for small-scale structure. At low masses, we find that COHERENT and late kinetic decoupling produce the strongest constraints on the model, while at high masses the leading constraints come from DM down-scattering at XENON1T and Borexino. Future improvement will come from $\mathrm{CE}\nu \mathrm{NS}$ data, ultralow threshold direct detection, and rare kaon decays.

The effective potential for the Aharonov-Bohm phase ${\theta }_H$ in the fifth dimension in GUT-inspired $SO(5)\times U(1)\times SU(3)$ gauge-Higgs unification is evaluated to show that dynamical electroweak symmetry breaking takes place with ${\theta }_H\ne 0$, where the four-dimensional Higgs boson mass of 125 GeV is generated at the quantum level. The cubic and quartic self-couplings $({\lambda }_3,{\lambda }_4)$ of the Higgs boson are found to satisfy universal relations, i.e., they are determined, to high accuracy, solely by ${\theta }_H$, irrespective of the values of other parameters in the model. For ${\theta }_H=0.1$ (0.15), ${\lambda }_3$ and ${\lambda }_4$ are smaller than those in the standard model by 7.7% (8.1%) and 30% (32%), respectively.

We show that standard identities and theorems for lattice models with $U(1)$ symmetry get reexpressed discretely in the tensorial formulation of these models. We also explain the geometrical analogy between the continuous lattice equations of motion and the discrete selection rules of the tensors. We further construct a gauge-invariant transfer matrix in arbitrary dimensions, show the equivalence with its gauge-fixed version in a maximal temporal gauge, and explain how a discrete Gauss’s law is always enforced. Moreover, we propose a noise-robust way to implement Gauss’s law in arbitrary dimensions, and we reformulate Noether’s theorem for global, local, continuous, or discrete Abelian symmetries: for each given symmetry, there is one corresponding tensor redundancy. We discuss semiclassical approximations for classical solutions with periodic boundary conditions in two solvable cases, and we show the correspondence of their weak coupling limit with the tensor formulation after Poisson summation. Finally, we briefly discuss connections with other approaches and implications for quantum computing.

We calculate the single transverse spin asymmetry in polarized proton-proton ($p^{\uparrow }+p$) and polarized proton-nucleus ($p^{\uparrow }+A$) collisions ($A_N$) generated by a partonic lensing mechanism. The polarized proton is considered in the quark-diquark model while its interaction with the unpolarized target is calculated using the small-$x$/saturation approach, which includes multiple rescatterings and small-$x$ evolution. The phase required for the asymmetry is caused by a final-state gluon exchange between the quark and diquark, as is standard in the lensing mechanism of Brodsky, Hwang, and Schmidt [Phys. Lett. B 530, 99 (2002)]. Our calculation combines the lensing mechanism with small-$x$ physics in the saturation framework. The expression we obtain for the asymmetry $A_N$ of the produced quarks has the following properties: (i) The asymmetry is generated by the dominant elastic scattering contribution and the $1/N_c^2$ suppressed inelastic contribution (with $N_c$ the number of quark colors). (ii) The asymmetry grows or oscillates with the produced quark’s transverse momentum $p_T$ until the momentum reaches the saturation scale $Q_s$, and then only falls off as $1/p_T$ for larger momenta. (iii) The asymmetry decreases with increasing atomic number $A$ of the target for $p_T$ below or near $Q_s$, but is independent of $A$ for $p_T$ significantly above $Q_s$. We discuss how these properties may be qualitatively consistent with the data on $A_N$ published by the PHENIX Collaboration [Phys. Rev. Lett. 123, 122001 (2019)] and with the preliminary data on $A_N$ reported by the STAR Collaboration [Proc. Sci., DIS2016 (2016) 212 [arXiv:1805.08875] ].

We investigate the tomographical structure of the pion and kaon in the light-cone quark model. In particular, we study the parton distribution amplitude (PDA) of the pion and kaon. We obtain the parton distribution function (PDF) and the generalized parton distributions of the pion and kaon. The valence quark PDA and PDF of the pion, after QCD evolution, are found to be consistent with the data from the E791 and the E615 experiments at Fermilab, respectively. Further, we investigate the transverse momentum distributions (TMDs) of the pion and kaon. We also discuss the unpolarized TMD evolution for the pion and kaon in this model.

We investigate nonlinear extensions of the holographic soft wall model proposed by Karch et al. [Phys. Rev. D 74, 015005 (2006)] with a positive quadratic dilaton. We consider a Higgs potential for the tachyonic field that brings a more natural realization of chiral symmetry breaking in the infrared regime. Utilizing the $\mathrm{AdS}/\mathrm{CFT}$ dictionary and holographic renormalization, we find the chiral condensate as a function of the quark mass. The nonlinearity of the Higgs potential leads to a nonlinear relation between the chiral condensate and the quark mass. Solving the effective Schrödinger equations for the field perturbations, we estimate meson masses and decay constants and evaluate their dependence on the quark mass. In the axial and pseudoscalar sector we find an interesting behavior for the decay constants as the quark mass increases. We also investigate the effect of a five-dimensional running mass for the tachyonic field. We conclude that nonlinear soft wall models with a Higgs potential for the tachyon and a positive quadratic dilaton do not provide spontaneous symmetry breaking in the chiral limit.

We develop a field theory with dissipation based on a finite range of wave propagation and associated gapped momentum states in the wave spectrum. We analyze the properties of the Lagrangian and the Hamiltonian with two scalar fields in different representations and show how the new properties of the two-field Lagrangian are related to Keldysh-Schwinger formalism. The proposed theory is non-Hermitian, and we discuss its properties related to $\mathcal{P}\mathcal{T}$ symmetry. The calculated correlation functions show a decaying oscillatory behavior related to gapped momentum states. We corroborate this result using path integration. The interaction potential becomes short-ranged due to dissipation. Finally, we observe that the proposed field theory represents a departure from the harmonic paradigm and discuss the implications of our theory for the Lagrangian formulation of hydrodynamics.