Fusion excitation functions and barrier distributions: A semiclassical approach

Fusion cross sections and barrier distributions are discussed and calculated in the framework of a semiclassical approximation for a variety of systems. An overall good description of the data is achieved

Weak lensing of large scale structure in the presence of screening

A number of alternatives to general relativity exhibit gravitational screening in the non-linear regime of structure formation. We describe a set of algorithms that can produce weak lensing maps of large scale structure in such theories and can be used to generate mock surveys for cosmological analysis. By analysing a few basic statistics we indicate how these alternatives can be distinguished from general relativity with future weak lensing surveys.Comment: 25 pages, 7 figures, accepted by JCAP. v2: references updat

Coupled channels analysis of the 16O + 28Si reaction near the Coulomb barrier

Abstract Good agreement with all the available experimental data on 16 O + 28 Si scattering and fusion in the energy range of E = 21–38 MeV was obtained with a deformed optical potential consistent with calculations based on nuclear structure information

Evidence for energy dependent interaction in one-particle transfer reactions between heavy ions

Abstract The recently measured proton stripping cross sections in the collision 16 O+ 208 Pb at 793 MeV [M.C. Mermaz et al., Z. Phys. A 326 (1987) 353] is analyzed in the semiclassical approximation. Taking into account an energy dependence in the interaction, consistent with the proton scattering data, an accurate description of the absolute cross sections is obtained

DiffEnc: Variational Diffusion with a Learned Encoder

Diffusion models may be viewed as hierarchical variational autoencoders (VAEs) with two improvements: parameter sharing for the conditional distributions in the generative process and efficient computation of the loss as independent terms over the hierarchy. We consider two changes to the diffusion model that retain these advantages while adding flexibility to the model. Firstly, we introduce a data- and depth-dependent mean function in the diffusion process, which leads to a modified diffusion loss. Our proposed framework, DiffEnc, achieves state-of-the-art likelihood on CIFAR-10. Secondly, we let the ratio of the noise variance of the reverse encoder process and the generative process be a free weight parameter rather than being fixed to 1. This leads to theoretical insights: For a finite depth hierarchy, the evidence lower bound (ELBO) can be used as an objective for a weighted diffusion loss approach and for optimizing the noise schedule specifically for inference. For the infinite-depth hierarchy, on the other hand, the weight parameter has to be 1 to have a well-defined ELBO

Enabling matter power spectrum emulation in beyond-ΛCDM cosmologies with COLA

We compare and validate COLA (COmoving Lagrangian Acceleration) simulationsagainst existing emulators in the literature, namely Bacco and Euclid Emulator2. Our analysis focuses on the non-linear response function, i.e., the ratiobetween the non-linear dark matter power spectrum in a given cosmology withrespect to a pre-defined reference cosmology, which is chosen to be the EuclidEmulator 2 reference cosmology in this paper. We vary three cosmologicalparameters, the total matter density, the amplitude of the primordial scalarperturbations and the spectral index. By comparing the COLA non-linear responsefunction with those computed from each emulator in the redshift range $0 \leq z\leq 3$, we find that the COLA method is in excellent agreement with the twoemulators for scales up to $k \sim 1 \ h$/Mpc as long as the deviations of thematter power spectrum from the reference cosmology are not too large. Wevalidate the implementation of massive neutrinos in our COLA simulations byvarying the sum of neutrino masses to three different values, $0.0$ eV, $0.058$eV and $0.15$ eV. We show that all three non-linear prescriptions used in thiswork agree at the $1\%$ level at $k \leq 1 \ h$/Mpc. We then introduce theEffective Field Theory of Dark Energy in our COLA simulations using the$N$-body gauge method. We consider two different modified gravity models inwhich the growth of structure is enhanced or suppressed at small scales, andshow that the response function with respect to the change of modified gravityparameters depends weakly on cosmological parameters in these models.<br

Testing Gravity on Cosmic Scales: A Case Study of Jordan-Brans-Dicke Theory

We provide an end-to-end exploration of a distinct modified gravitational theory in Jordan-Brans-Dicke (JBD) gravity, from an analytical and numerical description of the background expansion and linear perturbations, to the nonlinear regime captured with a hybrid suite of $N$-body simulations, to the parameter constraints from existing cosmological probes. The nonlinear corrections to the matter power spectrum due to baryons, massive neutrinos, and modified gravity are simultaneously modeled and propagated in the cosmological analysis for the first time. In the combined analysis of the Planck CMB temperature, polarization, and lensing reconstruction, Pantheon supernova distances, BOSS measurements of BAO distances, the Alcock-Paczynski effect, and the growth rate, along with the joint ($3\times2$pt) dataset of cosmic shear, galaxy-galaxy lensing, and overlapping redshift-space galaxy clustering from KiDS and 2dFLenS, we constrain the JBD coupling constant, $\omega_{\rm BD}>1540$ (95% CL), the effective gravitational constant, $G_{\rm matter}/G=0.997\pm0.029$, the sum of neutrino masses, $\sum m_{\nu}<0.12$ eV (95% CL), and the baryonic feedback amplitude, $B<2.8$ (95% CL), all in agreement with the standard model expectation. We show that the uncertainty in the gravitational theory alleviates the tension between KiDS$\times$2dFLenS and Planck to below $1\sigma$ and the tension in the Hubble constant between Planck and the direct measurement of Riess et al. (2019) down to ~$3\sigma$; however, we find no substantial model selection preference for JBD gravity relative to $\Lambda$CDM. We further show that the neutrino mass bound degrades by up to a factor of $3$ as the $\omega_{\rm BD}$ parameterization becomes more restrictive, and that a positive shift in $G_{\rm matter}/G$ suppresses the CMB damping tail in a way that might complicate future inferences of small-scale physics. (Abridged)Comment: 48 pages, 24 figures, PRD submitte