We present the data-driven late-time reconstruction of gravitational theories and dark energy models on cosmological scales. We showcase the power of present cosmological probes at constraining these models and quantify the knowledge of their properties that can be acquired through state of the art data. This reconstruction exploits the power of the effective field theory approach to dark energy and modified gravity phenomenology, which compresses the freedom in defining such models into a finite set of functions that can be reconstructed across cosmic times using cosmological data. We consider several model classes described within this framework and thoroughly discuss their phenomenology and data implications. We find that some models can alleviate the present discrepancy in the determination of the Hubble constant as inferred from the cosmic microwave background and as directly measured. This results in a statistically significant preference for the reconstructed theories over the standard cosmological model.

We describe directed searches for continuous gravitational waves from twelve well-localized nonpulsing candidate neutron stars in young supernova remnants using data from Advanced LIGO’s second observing run. We assumed that each neutron star is isolated and searched a band of frequencies from 15 to 150 Hz, consistent with frequencies expected from known young pulsars. After coherently integrating spans of data ranging from 12.0 to 55.9 days using the $\mathcal{F}$-statistic and applying data-based vetoes, we found no evidence of astrophysical signals. We set upper limits on intrinsic gravitational wave amplitude in some cases stronger than ${10}^{-25}$, generally about a factor of two better than upper limits on the same objects from Advanced LIGO’s first observing run.

Primordial black holes formed in an early postinflation matter-dominated epoch during preheating provide a novel pathway for a source of the dark matter that utilizes known physics in combination with plausible speculations about the role of quantum gravity. Two cases are considered here: survival of Planck-scale relics and an early universe accretion scenario for the formation of primordial black holes of asteroid-scale masses.

We write down and apply the linearized fluid and gravitational equations consistent with pseudo-Newtonian simulations, whereby Newtonian hydrodynamics is used with a pseudo-Newtonian monopole and standard Newtonian gravity for higher multipoles. We thereby eliminate the need to use mode function matching to identify the active nonradial modes in pseudo-Newtonian core-collapse supernova simulations, in favor of the less complex and less costly mode frequency matching method. In doing so, we are able to measure appropriate boundary conditions for a mode calculation.

The DAMA/LIBRA (DL) experiment shows $9.5\sigma$ evidence for an annual modulation in the (1–6) keV energy range, strongly suggesting that the observed modulation has a dark matter origin. However, the conventional interpretation in terms of weakly interacting massive particle–nucleon interaction is excluded by other experiments. We propose an alternative source of modulation in the form of neutrons, which have been liberated from surrounding material. Our computations are based on the so-called axion quark nugget (AQN) dark matter model, which was originally invented long ago to explain the similarity between the dark and visible cosmological matter densities, i.e., ${\mathrm{\Omega }}_{\mathrm{dark}}\sim {\mathrm{\Omega }}_{\text{visible}}$. In our proposal, the annual modulation is shown to be generated in the keV energy range, which is consistent with the DL observation in (1–6) keV range. This keV energy scale in our proposal is mostly determined by spectral properties of the neutrinos emitted by the AQN dark matter particles, while the absence of the modulation with energies above 6 keV is explained by a sharp cutoff in the neutrino’s energy spectrum at $\sim 15\mathrm{MeV}$. This proposal can be directly tested by COSINE-100, ANAIS-112, CYGNO, and other similar experiments. It can be also tested by studying the correlations between the signals from these experiments and the signatures from drastically different detectors designed for studies of infrasonic or seismic events using such instruments as distributed acoustic sensing.

The signum-Gordon model in $1+1$ dimensions possesses an exact solution with a discontinuity of the field at the light cone. Thus, the gradient energy of these waves is infinite whereas the energy of a part of the wave localized inside the light cone is finite and grows linearly with time. The initial data for such waves contain a field configuration which is null in space and its time derivative is proportional to the Dirac delta. We study regular initial data that lead to shocklike waves with finite gradient energy. We found that such waves exist only for a finite time and eventually decay in a cascade of oscillonlike structures. The pattern of decay is very similar to the one observed in the scattering of compact oscillons.

We study multi-Higgs final states in vector boson fusion (VBF) processes at the LHC and at future proton-proton colliders, focusing on the prospects for measurements at 27 and 100 TeV. We use an effective Lagrangian which includes higher-dimensional operators in the mass eigenstates which are relevant to VBF processes and relate this to specific parametrizations and models for new physics in the Higgs sector. We derive theoretical constraints on the parameter space from the unitarity of $2\to n$ scattering amplitudes and apply the results to $VV\to hh$ and $hhh$ processes, where $V=W$, $Z$. As a result, we present constraints on differential distributions as appropriate to the study of $VV\to hh$ and $hhh$ processes.

We consider electromagnetically neutral dark states that couple to the photon through higher dimensional effective operators, such as electric and magnetic dipole moment, anapole moment and charge radius operators. We investigate the possibility of probing the existence of such dark states, taking a Dirac fermion $\chi$ as an example, at several representative proton-beam experiments. As no positive signal has been reported, we obtain upper limits (or projected sensitivities) on the corresponding electromagnetic form factors for dark states lighter than several GeV. We demonstrate that while the current limits from proton-beam experiments are at most comparable with those from high-energy electron colliders, future experiments, such as DUNE and SHiP, will be able to improve the sensitivities to electric and magnetic dipole moment interactions, owing to their high intensity.

It has been pointed out that the mixing of an eV-scale sterile neutrino with active flavors can lead to a loss of sensitivity to the ${\theta }_{23}$ octant (sign of ${\sin }^2{\theta }_{23}-1/2$) in long baseline experiments, because the main oscillation probability $P_0=4{\sin }^2{\theta }_{23}{\sin }^2{\theta }_{13}{\sin }^2{\mathrm{\Delta }}_{31}$ can be degenerate with the sum of the interferences with the solar oscillation amplitude and an active-sterile oscillation amplitude in both neutrino and antineutrino oscillations, depending on the $CP$ phases. In this paper, we show that the above degeneracy is resolved by measuring the same beam at different baseline lengths. We demonstrate that the Tokai-to-Hyper-Kamiokande-to-Korea (T2HKK) experiment (one 187 kton fiducial volume water Cerenkov detector is placed at Kamioka, $L=295\mathrm{km}$, and another detector is put in Korea, $L\sim 1000\mathrm{km}$) exhibits a better sensitivity to the ${\theta }_{23}$ octant in those parameter regions where the experiment with the two detectors at Kamioka is insensitive to it. Therefore, if a hint of sterile-active mixings is discovered in short baseline experiments, T2HKK is a better option than the plan of placing two detectors at Kamioka. We also consider an alternative case where one detector is placed at Kamioka and a different detector is at Oki Islands, $L=653\mathrm{km}$, and show that this configuration also leads to a better sensitivity to the ${\theta }_{23}$ octant.

We scrutinize the penguin dominated $B_s\to K^{+}{K}^{-}$ decay mode involving $b\to s$ quark level transition in family nonuniversal $Z^{\prime }$ and vectorlike down quark model. There is discrepancy in the standard model branching ratio value of this mode with the experimental results reported by Belle, CDF, and LHCb Collaborations. Additionally, the measured values of CP-violating asymmetries $C_{K^{+}{K}^{-}}$ and $S_{K^{+}{K}^{-}}$ deviate from the SM predictions. We constrain the new parameter space by using the existing experimental limits on leptonic $B_s\to \ell \ell$ ($\ell =e,\mu ,\tau$) processes. We then check the effects of new physics on the branching ratio and CP-violating parameters of the $B_s\to K^{+}{K}^{-}$ process.

In this work we study the axial contributions to the hadronic light-by-light piece of the muon anomalous magnetic moment. We point out some theoretical ambiguities in previous estimates, and opt to perform a new evaluation using resonace chiral theory, that is free of them. As a result, we obtain $a_{\mu }^{\text{HLbL};A}=(0.8_{-0.8}^{+3.5})\times {10}^{-11}$, that might suggest a smaller value than most recent calculations, underlining the relevance of the off-shell prescription and the need for future work along this direction. Further, we find that our results depend critically on the asymptotic behavior of the form factors, and as such, emphasizes the relevance of future experiments at large photon virtualities. In addition, we present general results regarding the involved axial form factors description, comprehensively examining (and relating) the current approaches, that shall be of general interest.

The quadrupole moments of ground state baryons are discussed inn the framework of the $1/N_c$ expansion of QCD, where $N_c$ is the number of color charges. Theoretical expressions are first provided assuming an exact $SU(3)$ flavor symmetry, and then the effects of symmetry breaking are accounted for to linear order. The rather scarce experimental information available does not allow a detailed comparison between theory and experiment, so the free parameters in the approach are not determined. Instead, some useful new relations among quadrupole moments, valid even in the presence of first-order symmetry breaking, are provided. The overall predictions of the $1/N_c$ expansion are quite enlightening.

We present new calculations of the differential decay rates for $H\to {\ell }^{+}{\ell }^{-}\gamma$ with $\ell =e$ or $\mu$ in the Standard Model. The branching fractions and forward-backward asymmetries, defined in terms of the flight direction of the photon relative to the lepton momenta, depend on the cuts on energies and invariant masses of the final state particles. For typical choices of these cuts we find the branching ratios $B(H\to e\overline{e}\gamma )=5.8\times {10}^{-5}$ and $B(H\to \mu \overline{\mu }\gamma )=6.4\times {10}^{-5}$ and the forward-backward asymmetries ${\mathcal{A}}_{\mathrm{FB}}^{(e)}=0.343$ and ${\mathcal{A}}_{\mathrm{FB}}^{(\mu )}=0.255$. We provide compact analytic expressions for the differential decay rates for the use in experimental analyses.

In this work, we present an overview of experimental considerations relevant to the utilization of jets at a future electron-ion collider, a subject which has been largely overlooked up to this point. A comparison of jet-finding algorithms and resolution parameters is presented along with a detailed analysis of basic jet quantities, such as multiplicities and kinematic distributions. A characterization of the energy in the event not associated with a jet is also made. In addition, detector requirements and the effects of realistic detector resolutions are discussed. Finally, an example analysis is presented in which dijets are used to access the gluon helicity contribution to the spin of the proton.

The improved results on a direct search for a new $X(16.7\mathrm{MeV})$ boson that could explain the anomalous excess of $e^{+}{e}^{-}$ pairs observed in the decays of the excited ${}^8{\mathrm{Be}}^{*}$ nuclei (“Berillium or X17 anomaly”) are reported. Interestingly, new recent results in the nuclear transitions of another nucleus, ${}^4\mathrm{He}$, seems to support this anomaly spurring the need for an independent measurement. If the $X$ boson exists, it could be produced in the bremsstrahlung reaction $e^{-}Z\to e^{-}ZX$ by a high energy beam of electrons incident on the active target in the NA64 experiment at the CERN Super Proton Synchrotron and observed through its subsequent decay into $e^{+}{e}^{-}$ pairs. No evidence for such decays was found from the combined analysis of the data samples with total statistics corresponding to $8.4\times {10}^{10}$ electrons on target collected in 2017 and 2018. This allows one to set new limits on the $X-e^{-}$ coupling in the range $1.2\times {10}^{-4}\lesssim {\epsilon }_e\lesssim 6.8\times {10}^{-4}$, excluding part of the parameter space favored by the X17 anomaly, and setting new bounds on the mixing strength of photons with dark photons ($A^{\prime }$) with a mass $\lesssim 24\mathrm{MeV}$. For the 2018 run, the setup was optimized to probe the region of parameter space characterized by a large coupling $\epsilon$. This allowed a significant improvement in sensitivity despite a relatively modest increase in statistics.

We introduce a description of a minimal surface in a space with boundary, as the world hypersurface that the entangling surface traces. It does so by evolving from the boundary to the interior of the bulk under an appropriate geometric flow, whose parameter is the holographic coordinate. We specify this geometric flow for arbitrary bulk geometry. In the case of pure AdS spaces, we implement a perturbative approach for the solution of the flow equation around the boundary. We systematically study both the form of the perturbative solution as well as its dependence on the boundary conditions. This expansion is sufficient for the determination of all the divergent terms of the holographic entanglement entropy, including the logarithmic universal terms in odd spacetime bulk dimensions, for an arbitrary entangling surface, in terms of the extrinsic geometry of the latter.

The Landau-Khalatnikov-Fradkin transformations (LKFTs) represent an important tool for probing the gauge dependence of the correlation functions within the class of linear covariant gauges. Recently these transformations have been derived from first principles in the context of non-Abelian gauge theory (QCD) introducing a gauge invariant transverse gauge field expressible as an infinite power series in a Stueckelberg field. In this work we explicitly calculate the transformation for the gluon propagator, reproducing its dependence on the gauge parameter at the one-loop level and elucidating the role of the extra fields involved in this theoretical framework. Later on, employing a unifying scheme based upon the Becchi-Rouet-Stora-Tyutin symmetry and a resulting generalized Slavnov-Taylor identity, we establish the equivalence between the LKFTs and the Nielsen identities which are also known to connect results in different gauges.

We investigate instabilities of $F(R)$-charged ${\mathrm{AdS}}_4$ black holes by a massive charged scalar field in a linear perturbation regime. We study tachyonic instabilities as the near horizon scalar condensation in a model of $F(R)$ gravity with planar horizon and investigate properties of possible phase transitions. The results show that such transitions are sensitive to the first derivative of $F(R)$ with respect to $R$ in that the larger its value, the higher the critical temperature, thus resulting in a new generation of high-temperature superconductors. Also, for a certain range of parameters, $F(R)$-charged ${\mathrm{AdS}}_4$ black holes suffer from superradiant instability. We consider the effects of the scalar mass and charge on such instabilities and conclude that Reissner-Nordstrom (RN) black holes decay into small hairy black holes that have a charged scalar condensate floating near the horizon. It is shown that the existence of phase transition at the critical temperature leading to a hairy black hole solution emerges for $T<T_c$, while RN black holes exist for $T>T_c$. The effect of $F(R)$ on the critical temperature is subsequently investigated in the case of superradiant instability, showing that higher critical temperatures would be possible in $F(R)$ gravity. We also check the stability of hairy black holes and show that the resulting hairy solution can be considered as a possible endpoint of superradiant instability of a small charged black hole.

Two strategies for constructing general geometric operators in all dimensional loop quantum gravity are proposed. The different constructions mainly come from the two different regularization methods for the basic building blocks of the spatial geometry. The first regularization method is a generalization of the regularization of the length operator in standard ($1+3$)-dimensional loop quantum gravity, while the second method is a natural extension of those for standard ($\mathrm{D}-1$)-area and usual D-volume operators. Two versions of general geometric operators to measure arbitrary $m$-areas are constructed, and their properties are discussed and compared. They serve as valuable candidates to study the quantum geometry in arbitrary dimensions.

We demonstrate separability of conformally coupled scalar field equations in general (off-shell) Kerr—Newman-Unti-Tamburino—anti–de Sitter spacetimes in all dimensions. The separability is intrinsically characterized by the existence of a complete set of mutually commuting conformal wave operators that can be constructed from a hidden symmetry of the principal Killing-Yano tensor. By token of conformal symmetry, the separability also works for any Weyl rescaled (off-shell) metrics. This is especially interesting in four dimensions where it guarantees separability of a conformally coupled scalar field in the general Plebański-Demiański spacetime.