The next generation of galaxy surveys will provide highly accurate measurements of the large-scale structure of the Universe, allowing for more stringent tests of gravity on cosmological scales. Higher-order statistics are a valuable tool to study the non-Gaussianities in the matter field and to break degeneracies between modified gravity and other physical or nuisance parameters. However, understanding from first principles the behavior of these correlations is essential to characterize deviations from General Relativity (GR), and the purpose of this work. This work uses contemporary ideas of standard perturbation theory on biased tracers to characterize the three-point correlation function at tree level for modified gravity models with a scale-dependent gravitational strength, and applies the theory to two specific models [$f(R)$ and DGP] that are representative for Chameleon and Vainshtein screening mechanisms. Additionally, we use a multipole decomposition, which apart from speeding up the algorithm to extract the signal from data, also helps to visualize and characterize GR deviations.

Anisotropic inflation is a model that succeeded in explaining statistical anisotropy. Warm inflation is a model that succeeded in providing a mechanism of reheating during inflation. We study anisotropic warm inflation focusing on the cosmic no-hair conjecture. In the anisotropic warm inflation, the condition for making anisotropy survive is clarified. By assuming a constant value for the dissipation ratio, we find exact solutions of power-law anisotropic warm inflation, and investigate the phase space structure of general solutions. It turns out that whether the anisotropy during inflation survives or not depends on the competition of the potential that drives anisotropic inflation against dissipation of an inflaton field. Anisotropic warm inflation will be realized if the decaying process is not efficient.

The field of machine learning has drawn increasing interest from various other fields due to the success of its methods at solving a plethora of different problems. An application of these has been to train artificial neural networks to solve differential equations without the need of a numerical solver. This particular application offers an alternative to conventional numerical methods, with advantages such as lower memory required to store solutions, parallelization, and, in some cases, a lower overall computational cost than its numerical counterparts. In this work, we train artificial neural networks to represent a bundle of solutions of the differential equations that govern the background dynamics of the Universe for four different models. The models we have chosen are $\mathrm{\Lambda }\mathrm{CDM}$, the Chevallier-Polarski-Linder parametric dark energy model, a quintessence model with an exponential potential, and the Hu-Sawicki $f(R)$ model. We use the solutions that the networks provide to perform statistical analyses to estimate the values of each model’s parameters with observational data; namely, estimates of the Hubble parameter from cosmic chronometers, type Ia supernovae data from the Pantheon compilation, and measurements from baryon acousstic oscillations. The results we obtain for all models match similar estimations done in the literature using numerical solvers. In addition, we estimate the error of the solutions that the trained networks provide by comparing them with the analytical solution when there is one, or to a high-precision numerical solution when there is not. Through these estimations we find that the error of the solutions is at most $\sim 1\%$ in the region of the parameter space that concerns the 95% confidence regions that we find using the data, for all models and all statistical analyses performed in this work. Some of these results are made possible by improvements to the method of solving differential equations with artificial neural networks conceived in this work.

We study the performance of three pairs of tilted, and a pair of untilted, $\mathrm{\Lambda }$ cold dark matter ($\mathrm{\Lambda }\mathrm{CDM}$) cosmological models, with three of these four pairs allowing for nonflat spatial hypersurfaces, against cosmic microwave background (CMB) temperature and polarization power spectrum data (P18), measurements of the Planck 2018 lensing potential power spectrum (lensing), and a large compilation of non-CMB data (non-CMB). For the eight models, we measure cosmological parameters and study whether or not pairs of the datasets (as well as subsets of them) are mutually consistent in these models. Half of these models allow the lensing consistency parameter $A_L$, which rescales the gravitational potential power spectrum, to be an additional free parameter to be determined from data, while the other three have $A_L=1$ which is the theoretically expected value. The pair of untilted nonflat $\mathrm{\Lambda }\mathrm{CDM}$ models are incompatible with P18 data. The tilted spatially flat models assume the usual primordial spatial inhomogeneity power spectrum that is a power law in wave number. The tilted nonflat models assume either the primordial power spectrum used in the Planck group analyses [Planck $P(q)$], which has recently been numerically shown to be a good approximation to what is quantum-mechanically generated from a particular choice of closed inflation model initial conditions, or a recently computed power spectrum [new $P(q)$] that quantum-mechanically follows from a different set of nonflat inflation model initial conditions. In the tilted nonflat models with $A_L=1$, we find differences between P18 data and non-CMB data cosmological parameter constraints, which are large enough to rule out the Planck $P(q)$ model at $3\sigma$ but not the new $P(q)$ model. No significant differences are found when cosmological parameter constraints obtained with two different datasets are compared within the standard tilted flat $\mathrm{\Lambda }\mathrm{CDM}$ model. While both P18 data and non-CMB data separately favor a closed geometry, with spatial curvature density parameter ${\mathrm{\Omega }}_k<0$, when $\mathrm{P}18+\mathrm{non}\text{−}\mathrm{CMB}$ data are jointly analyzed the evidence in favor of nonflat hypersurfaces subsides. Differences between P18 data and non-CMB data cosmological constraints subside when $A_L$ is allowed to vary. From the most restrictive $\mathrm{P}18+\mathrm{lensing}+\mathrm{non}\text{−}\mathrm{CMB}$ data combination, we get almost model-independent constraints on the cosmological parameters and find that the $A_L>1$ option is preferred over the ${\mathrm{\Omega }}_k<0$ one, with the $A_L$ parameter, for all models, being larger than unity by $\sim 2.5\sigma$. According to the deviance information criterion, in the $\mathrm{P}18+\mathrm{lensing}+\mathrm{non}\text{−}\mathrm{CMB}$ analysis, the varying $A_L$ option is on the verge of being strongly favored over the $A_L=1$ one, which could indicate a problem for the standard tilted flat $\mathrm{\Lambda }\mathrm{CDM}$ model. These data are consistent with flat spatial hypersurfaces but more and better data could improve the constraints on ${\mathrm{\Omega }}_k$ and might alter this conclusion. Error bars on some cosmological parameters are significantly reduced when non-CMB data are used jointly with $\mathrm{P}18+\mathrm{lensing}$ data. For example, in the tilted flat $\mathrm{\Lambda }\mathrm{CDM}$ model for data, the Hubble constant $H_0=68.09\pm 0.38\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, which is consistent with that from a median statistics analysis of a large compilation of $H_0$ measurements, as well as with a number of local measurements of the cosmological expansion rate. This $H_0$ error bar is 31% smaller than that from $\mathrm{P}18+\mathrm{lensing}$ data alone.

Several cosmological tensions have emerged in light of recent data, most notably in the inferences of the parameters $H_0$ and ${\sigma }_8$. We explore the possibility of alleviating both these tensions simultaneously by means of the Albrecht-Skordis “quintessence” potential. The field can reduce the size of the sound horizon $r_s^{*}$ while concurrently suppressing the power in matter density fluctuations before it comes to dominate the energy density budget today. Interestingly, this rich set of dynamics is governed entirely by one free parameter that is of $\mathcal{O}(10)$ in Planck units. We find that the inferred value of $H_0$ can be increased, while that of ${\sigma }_8$ can be decreased, both by $\approx 1\sigma$ compared to the $\mathrm{\Lambda }\mathrm{CDM}$ case. However, ultimately the model is disfavored by Planck and BAO data alone, compared to the standard $\mathrm{\Lambda }\mathrm{CDM}$ model, with a $\mathrm{\Delta }{\chi }^2\approx +6$. When including large scale structure and supernova data we find $\mathrm{\Delta }{\chi }^2\approx +1$. We note that historically much attention has been focused on preserving the three angular scales ${\theta }_D$, ${\theta }_{\mathrm{EQ}}$, and ${\theta }_s^{*}$ to their $\mathrm{\Lambda }\mathrm{CDM}$ values. Our work presents an example of how, while doing so indeed maintains a relatively good fit to the cosmic microwave background data for an increased number of ultrarelativistic species, it is a priori insufficient in maintaining such a fit in more general model spaces.

A significant pointlike component from the small-scale (or discrete) structure in the ${\mathrm{H}}_2$ interstellar gas might be present in the Fermi-LAT data, but modeling this emission relies on observations of rare gas tracers only available in limited regions of the sky. Identifying this contribution is important to discriminate $\gamma$-ray point sources from interstellar gas, and to better characterize extended $\gamma$-ray sources. We design and train convolutional neural networks to predict this emission where observations of these rare tracers do not exist, and discuss the impact of this component on the analysis of the Fermi-LAT data. In particular, we evaluate prospects to exploit this methodology in the characterization of the Fermi-LAT Galactic center excess through accurate modeling of pointlike structures in the data to help distinguish between a pointlike or smooth nature for the excess. We show that deep learning may be effectively employed to model the $\gamma$-ray emission traced by these rare ${\mathrm{H}}_2$ proxies within statistical significance in data-rich regions, supporting prospects to employ these methods in yet unobserved regions.

Scorpius X-1 (Sco X-1) has long been considered one of the most promising targets for detecting continuous gravitational waves with ground-based detectors. Observational searches for Sco X-1 have achieved substantial sensitivity improvements in recent years, to the point of starting to rule out emission at the torque-balance limit in the low-frequency range $\sim 40–180\mathrm{Hz}$. In order to further enhance the detection probability, however, there is still much ground to cover for the full range of plausible signal frequencies $\sim 20–1500\mathrm{Hz}$, as well as a wider range of uncertainties in binary orbital parameters. Motivated by this challenge, we have developed binaryweave, a new search pipeline for continuous waves from a neutron star in a known binary system such as Sco X-1. This pipeline employs a semicoherent StackSlide $\mathcal{F}$-statistic using efficient lattice-based metric template banks, which can cover wide ranges in frequency and unknown orbital parameters. We present a detailed timing model and extensive injection-and-recovery simulations that illustrate that the pipeline can achieve high detection sensitivities over a significant portion of the parameter space when assuming sufficiently large (but realistic) computing budgets. Our studies further underline the need for stricter constraints on the Sco X-1 orbital parameters from electromagnetic observations, in order to be able to push sensitivity below the torque-balance limit over the entire range of possible source parameters.

We look at the mass distribution of the $D_s^{+}{\pi }^{-}$ in the $B^0\to {\overline{D}}^0{D}_s^{+}{\pi }^{-}$ decay, where a peak has been observed in the region of the $D_s^{*}\rho$, $D^{*}{K}^{*}$ thresholds. By creating these two channels together with a ${\overline{D}}^0$ in $B^0$ decay and letting them interact as coupled channels, we obtain a structure around their thresholds, short of producing a bound state, which leads to a peak in the $D_s^{+}{\pi }^{-}$ mass distribution in the $B^0\to {\overline{D}}^0{D}_s^{+}{\pi }^{-}$ decay. We conclude that the interaction between the $D^{*}{K}^{*}$ and $D_s^{*}\rho$ is essential to produce the cusp structure that we associate to the recently seen $T_{c\overline{s}}(2900)$, and that its experimental width is mainly due to the decay width of the $\rho$ meson. The peak obtained together with a smooth background reproduces fairly well the experimental mass distribution observed in the $B_0\to {\overline{D}}^0{D}_s^{+}{\pi }^{-}$ decay.

In the Grimus-Neufeld model (GNM) the neutrino mass generation from an extended Higgs sector leads to bounds for charged lepton flavor violating (cLFV) processes. Here we update bounds from a previous study by extending the parameter space to a nonvanishing Majorana phase of the Pontecorvo-Maki-Nakagawa-Sakata matrix and to heavier charged Higgs boson masses. Three-body cLFV decays are shown to contribute significantly in the large mass regions, as the boxes are enhanced relatively to photonic diagrams. This is in contrast to the smaller mass region studied before, in which the two-body decays tightly restrict the parameter space. The Majorana phase is shown to change limits within 1 order of magnitude. The tiny seesaw scale is assumed, which makes the cLFV decays in the GNM similar to the cLFV decays in the scotogenic model and the scoto-seesaw models.

I show that breaking $B-L$ by one unit of this charge is suitable for neutrino mass generation through an inverse seesaw mechanism, stabilizing a dark matter candidate without supersymmetry, as well as solving the muon anomalous magnetic moment and the $W$ mass deviation via dark field contributions. The new physics is governed by the residual $Z_3$ symmetry of $B-L$ isomorphic to the center of the color group, instead of the well-studied matter parity.

We investigate what it takes for the axion to address the strong $CP$ problem in the presence of explicit Peccei-Quinn symmetry breaking effects besides the strong interaction. In cases where the Peccei-Quinn-Higgsing scalar field directly couples to the Standard Model sector, it is pointed out that existing fifth force experiments can set better constraints on the axion quality over neutron electric dipole moment.

Quantum electrodynamics in $1+1$ dimensions (Schwinger model) on an interval admits lattice discretization with a finite-dimensional Hilbert space and is often used as a testbed for quantum and tensor network simulations. In this work we clarify the precise mapping between the boundary conditions in the continuum and lattice theories. In particular we show that the conventional Gauss law constraint commonly used in simulations induces a strong boundary effect on the charge density, reflecting the appearance of fractionalized charges. Further, we obtain by bosonization a number of exact analytic results for local observables in the massless Schwinger model. We compare these analytic results with the simulation results obtained by the density matrix renormalization group method and find excellent agreements.

The “intermediate window quantity” of the hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon allows for a high-precision comparison between the data-driven approach and lattice QCD. The existing lattice results, which presently show good consistency among each other, are in strong tension with the data-driven determination. In order to check for a potentially common source of systematic error of the lattice calculations, which are all based on the time-momentum representation (TMR), we perform a calculation using a Lorentz-covariant coordinate-space (CCS) representation. We present results for the isovector and the connected strange-quark contributions to the intermediate window quantity at a reference point in the $(m_{\pi },m_K)$ plane, in the continuum and infinite-volume limit, based on four different lattice spacings. Our results are in good agreement with those of the recent TMR-based Mainz-CLS publication.

The Abelian decomposition of QCD tells that there are two types of gluons, the color neutral neurons and colored chromons. We propose to confirm the Abelian decomposition testing the existence of two types of gluon jets experimentally. We predict that one quarter of the gluon jet is made of the neurons which has the color factor $3/4$ and the sharpest jet radius and smallest charged particle multiplicity, while the three quarters of the gluon jet are made of the chromons with the color factor $9/4$, which have the broadest jet radius (broader than the quark jet). Moreover, we argue that the neuron jet has a distinct color flow which forms an ideal color dipole, while the quark and chromon jets have distorted dipole pattern. To test the plausibility of this proposal, we suggest to analyze the gluon distribution against the jet shape (the sphericity) and/or particle multiplicity from the existing gluon jet events and look for two distinct peaks in the distribution.

Using dispersive methods, we study the $B\to {\gamma }^{*}$ form factors underlying the decay $B^{-}\to {\ell }^{-}{\overline{\nu }}_{\ell }{\ell }^{\prime -}{\ell }^{\prime +}$. We discuss the ambiguity that arises from a separation of the full $B^{-}\to {\ell }^{-}{\overline{\nu }}_{\ell }{\ell }^{\prime -}{\ell }^{\prime +}$ amplitude into a hadronic tensor and a final-state-radiation piece, including effects from nonvanishing lepton masses. For the eligibility of a dispersive treatment, we propose a decomposition of the hadronic part that leads to four form factors that are free of kinematic singularities. By establishing a set of dispersion relations, we then relate the $B\to {\gamma }^{*}$ form factors to the well-known $B\to V$, $V=\omega (782),\rho (770)$, analogs. Using the combination of a series expansion in a conformal variable and a vector-meson-dominance ansatz to parametrize the $B\to {\gamma }^{*}$ form factors, we infer the values of the associated unknown parameters from the available input on $B\to V$. The phenomenological application of our formalism includes the determination of the branching ratios and forward-backward asymmetries of the process $B^{-}\to {\ell }^{-}{\overline{\nu }}_{\ell }{\ell }^{\prime -}{\ell }^{\prime +}$.

The decay ${\eta }_c(2S)\to {\pi }^{+}{\pi }^{-}\eta$ is searched for through the radiative transition $\psi (3686)\to \gamma {\eta }_c(2S)$ using 448 million $\psi (3686)$ events accumulated at the BESIII detector. The first evidence of ${\eta }_c(2S)\to {\pi }^{+}{\pi }^{-}\eta$ is found with a statistical significance of $3.5\sigma$. The product of the branching fractions of $\psi (3686)\to \gamma {\eta }_c(2S)$ and ${\eta }_c(2S)\to {\pi }^{+}{\pi }^{-}\eta$ is measured to be $\mathrm{Br}(\psi (3686)\to \gamma {\eta }_c(2S))\times \mathrm{Br}({\eta }_c(2S)\to {\pi }^{+}{\pi }^{-}\eta )=(2.97\pm 0.81\pm 0.26)\times {10}^{-6}$, where the first uncertainty is statistical and the second one is systematic. The branching fraction of the decay ${\eta }_c(2S)\to {\pi }^{+}{\pi }^{-}\eta$ is determined to be $\mathrm{Br}({\eta }_c(2S)\to {\pi }^{+}{\pi }^{-}\eta )=(42.4\pm 11.6\pm 3.8\pm 30.3)\times {10}^{-4}$, where the third uncertainty is transferred from the uncertainty of the branching fraction of $\psi (3686)\to \gamma {\eta }_c(2S)$.

Using $4.5{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ annihilation data samples collected at center-of-mass energies ranging from 4.600 to 4.698 GeV with the BESIII detector at the BEPCII collider, we measured the absolute branching fraction for the inclusive semileptonic decay ${\mathrm{\Lambda }}_c^{+}\to X{e}^{+}{\nu }_e$, where $X$ refers to any possible particle system. The branching fraction of the decay is determined to be $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to X{e}^{+}{\nu }_e)=(4.06\pm 0.10_{\mathrm{stat}}\pm 0.09_{\mathrm{syst}})\%$. Our result improves the precision of previous measurements of $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to X{e}^{+}{\nu }_e)$ by more than threefold. Using the known ${\mathrm{\Lambda }}_c^{+}$ lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons, we measure the ratio of inclusive semileptonic decay widths $\mathrm{\Gamma }({\mathrm{\Lambda }}_c^{+}\to X{e}^{+}{\nu }_e)/\overline{\mathrm{\Gamma }}(D\to X{e}^{+}{\nu }_e)=1.28\pm 0.05$, where statistical and systematic uncertainties are combined.

In this work we propose a correspondence between black hole entropy and a topological quantity defined for projective spaces based on the real, complex, and quaternion numbers. After interpreting Weinstein’s integer as the normalized volume of the quantum phase space, whose logarithm gives place to the area law (in the real case) and to logarithmic corrections with $-\frac{1}{2}$ and $-\frac{3}{2}$ coefficients (in the complex and quaternionic cases, respectively), the exact Bekenstein-Hawking entropy is obtained when certain equally spaced spectrum for the event horizon area is imposed. Even more, the minimal area(s) which emerge from our model, are of the form $4\log k$, $k\in \{2,4,16\}$, in complete agreement with previous works. Finally, the role played by global (complex and quaternionic) phases in different descriptions of black hole entropy is clarified.

As constraints on ultralight axionlike particles (ALPs) tighten, models with multiple species of ultralight ALP are of increasing interest. We perform simulations of two-ALP models with particles in the currently supported range of plausible masses. The code we modified, ultradark.jl, not only allows for multiple species of ultralight ALP with different masses, but also different self-interactions and interfield interactions. This allows us to perform the first three-dimensional simulations of two-field ALPs with self-interactions and interfield interactions. Our simulations show that having multiple species and interactions introduces different phenomenological effects as compared to a single field, noninteracting scenarios. In particular, we explore the dynamics of solitons. Interacting multispecies ultralight dark matter has different equilibrium density profiles as compared to single-species and/or noninteracting ultralight ALPs. As seen in earlier work, attractive interactions tend to contract the density profile while repulsive interactions spread out the density profile. We also explore collisions between solitons comprised of distinct axion species. We observe a lack of interference patterns in such collisions, and that resulting densities depend on the relative masses of the ALPs and their interactions.

At times prior to big bang nucleosynthesis, the Universe could show a primordial structure formation period if dominated by a fast oscillating inflaton field during reheating. In this context, we have postulated a new mechanism of primordial black hole formation [Padilla et al., Phys. Rev. D, 106, 023519 (2022)], that draws on the analogy between an extended reheating era and the scalar field dark matter model, contemplating the gravitational collapse of inflaton halos and inflaton stars. In this paper we look at the requirements for the realization of this new mechanism. We show that a generic primordial power spectrum with a peak at small scales is most suitable for the production of a considerable number of primordial black holes (PBHs). When such a requirement is met, and if reheating lasts long enough, large populations of PBHs with $M_{\mathrm{PBH}}\sim 1\mathrm{gram}$ may be produced. We find, in particular, that the mass fraction of PBHs is orders of magnitude larger than that obtained when PBHs form via direct collapse in a Universe dominated by radiation or pressureless dust. Looking at observable implications of our findings, we explore the possibility that Planck mass relic remnants of the evaporation of the PBHs could contribute to be the totality of the dark matter in the Universe.