Detection Feasibility of Cluster-Induced CMB Polarization

Galaxy clusters can potentially induce sub-$\mu$K polarization signals in the CMB with characteristic scales of a few arcminutes in nearby clusters. We explore four such polarization signals induced in a rich nearby cluster and calculate the likelihood for their detection by the currently operational SPTpol, advanced ACTpol, and the upcoming Simons Array. In our feasibility analysis we include instrumental noise, primordial CMB anisotropy, statistical thermal SZ cluster signal, and point source confusion, assuming a few percent of the nominal telescope observation time of each of the three projects. Our analysis indicates that the thermal SZ intensity can be easily mapped in rich nearby clusters, and that the kinematic SZ intensity can be measured with high statistical significance toward a fast moving nearby cluster. The detection of polarized SZ signals will be quite challenging, but could still be feasible towards several very rich nearby clusters with exceptionally high SZ intensity. The polarized SZ signal from a sample of $\sim 20$ clusters can be statistically detected at $S/N \sim 3$, if observed for several months.Comment: 9 pages, 6 figures, submitted to MNRA

Effect of light Sr doping on the spin-state transition in LaCoO_3

We present an inelastic neutron scattering study of the low energy crystal-field excitations in the lightly doped cobalt perovskite La_0.998Sr_0.002CoO_3. In contrast to the parent compound LaCoO_3 an inelastic peak at energy transfer ~0.75 meV was found at temperatures below 30 K. This excitation apparently corresponds to a transition between a ground state orbital singlet and a higher excited orbital doublet, originating from a high-spin triplet split by a small trigonal crystal field. Another inelastic peak at an energy transfer ~0.6 meV was found at intermediate temperatures starting from T > 30 K. This confirms the presence of a thermally induced spin-state transition from the low-spin Co^3+ to a magnetic high-spin state in the non-disturbed LaCoO_3 matrix. We suggest that hole doping of LaCoO_3 leads to the creation of a magnetic polaron and hence to the low-to-high spin state transition on the relevant Co sites.Comment: 4 pages, 2 figures; based on a talk given at ICM'06, Kyoto; to appear in JMM

CMB lensing from Planck PR4 maps

We reconstruct the Cosmic Microwave Background (CMB) lensing potential on the latest Planck CMB PR4 (NPIPE) maps, which include slightly more data than the 2018 PR3 release, and implement quadratic estimators using more optimal filtering. We increase the reconstruction signal to noise by almost $20\%$, constraining the amplitude of the CMB-marginalized lensing power spectrum in units of the Planck 2018 best-fit to $1.004 \pm 0.024$ ($68\%$ limits), which is the tightest constraint on the CMB lensing power spectrum to date. For a base $\Lambda$CDM cosmology we find $\sigma_8 \Omega_m^{0.25} = 0.599\pm 0.016$ from CMB lensing alone in combination with weak priors and element abundance observations. Combination with baryon acoustic oscillation data gives tight $68\%$ constraints on individual $\Lambda$CDM parameters $\sigma_8 = 0.814\pm 0.016$, $H_0 = 68.1^{+1.0}_{-1.1}$km s$^{-1}$ Mpc$^{-1}$, $\Omega_m = 0.313^{+0.014}_{-0.016}$. Planck polarized maps alone now constrain the lensing power to $7\%$.Comment: 15 pages, 9 figures, 4 tables. Matches version accepted for publicatio

Data analysis for high-sensitivity cosmic microwave background observations

In recent decades, the cosmic microwave background radiation (CMB) has been one of the most important tools in cosmology. Due to its primordial origin, the CMB holds information about the early universe and how the universe evolved with time. Inferring cosmological information from the CMB is therefore essential for learning more about the universe. Our abilities to produce high-precision CMB measurements have progressed immensely over the years, which helped to constrain the standard cosmological model with remarkable accuracy. As CMB measurements improve, efforts to improve our analysis methods continue with it. The main aim of the work presented in this thesis is to continue this endeavour for improving our ability to extract information from CMB measurements. We first explore several filtering methods for lensing reconstruction, and also devise a new filtering step. We show the benefits of using an optimal filter for upcoming ground-based CMB experiments. We adopt our lensing reconstruction method to test how instrumental systematics may affect lensing reconstruction results of an experiment similar to the Simons Observatory (SO), and show how some of the resulting lensing biases might be mitigated. We continue by using our lensing reconstruction pipeline to present new lensing results from a recent release of CMB maps from the Planck collaboration which are more accurate on large scales compared to the previous Planck analysis method. We show how the uncertainty of different cosmological parameters benefits from the improved reconstruction accuracy. We conclude by looking into a different CMB effect — the effect of Rayleigh scattering on the CMB anisotropies. We demonstrate a possible pipeline for extracting the Rayleigh signal from multi-frequency CMB measurements, and forecast the ability of detecting the Rayleigh signal from an SO-like experimen

Contract B590089: Technical Evaluation of the Pu Cluster Calculations

Using Synchrotron-Radiation-based Photoelectron Spectroscopy and X-ray Absorption Spectroscopy, the theoretical results within recent progress reports supplied under Contract B590089 have been evaluated. Three appendices are included: A is from Progress Report I; B is from Progress Report II; and C is from an earlier calculation by M. Ryzhkov. The comparisons between the LLNL experimental data and the Russian calculations are quite favorable. The Cluster calculations may represent a new and useful avenue to address unresolved questions within the field of actinide electron structure, particularly that of Pu

Instrumental systematics biases in CMB lensing reconstruction: a simulation-based assessment

Weak gravitational lensing of the cosmic microwave background (CMB) is an important cosmological tool that allows us to learn about the structure, composition and evolution of the Universe. Upcoming CMB experiments, such as the Simons Observatory (SO), will provide high-resolution and low-noise CMB measurements. We consider the impact of instrumental systematics on the corresponding high-precision lensing reconstruction power spectrum measurements. We simulate CMB temperature and polarization maps for an SO-like instrument and potential scanning strategy, and explore systematics relating to beam asymmetries and offsets, boresight pointing, polarization angle, gain drifts, gain calibration and electric crosstalk. Our analysis shows that the majority of the biases induced by the systematics we modeled are below a detection level of ∼0.6σ. We discuss potential mitigation techniques to further reduce the impact of the more significant systematics, and pave the way for future lensing-related systematics analyses

Inequivalent representations of commutator or anticommutator rings of field operators and their applications

Hamiltonian of a system in quantum field theory can give rise to infinitely many partition functions which correspond to infinitely many inequivalent representations of the canonical commutator or anticommutator rings of field operators. This implies that the system can theoretically exist in infinitely many Gibbs states. The system resides in the Gibbs state which corresponds to its minimal Helmholtz free energy at a given range of the thermodynamic variables. Individual inequivalent representations are associated with different thermodynamic phases of the system. The BCS Hamiltonian of superconductivity is chosen to be an explicit example for the demonstration of the important role of inequivalent representations in practical applications. Its analysis from the inequivalent representations' point of view has led to a recognition of a novel type of the superconducting phase transition.Comment: 25 pages, 6 figure