Session SS01: V: Large: Cosmology and the CMB

Photometric Redshift Challenges: Rubin Observatory and Beyond

Most probes of cosmology rely on determining the relationship between some observable quantity and redshift.  For many experiments such as the Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST), those redshifts must be inferred based on information from imaging.  The resulting photometric redshift estimates -- also known as photo-z's -- have substantial uncertainties and can be biased.  In this talk I will highlight some of the foremost challenges we will face in using photometric redshifts from next-generation experiments, as well as key avenues for progress.  We wish both to improve the performance of photo-z methods -- i.e., how well we can predict the redshifts of individual objects -- as well as the statistical characterization of redshift distributions, as associated uncertainties may be a dominant systematic. I will highlight new progress we have made on improving the fidelity of predictions for redshift probability distribution functions via machine learning-based methods, ensuring that they in fact fulfill the statistical definition of a PDF; these methods can be applied to PDF predictions made for any purpose.  I will also describe the role that spectroscopic campaigns with an improved DESI instrument or a Stage V Spectroscopic Facility (Spec-S5) could play in improving both the performance and characterization of photo-z's.   

New parametrization and results on testing deviations from general relativity in cosmology

We present a new phenomenological parametrization to test deviations from general relativity at cosmological scales based on the perturbed Einstein's equations. We then present current constraints from applying the parametrization to current cosmological data sets from the Cosmic Microwave Radiation, Baryon Acoustic Oscillations, Redshift Space Distortion, 3 X 2 pts clustering and weak lensing, and supernova data. We report tensions found with general relativity along with a bayesian model selection analysis about their significance.   

Probing Physics Beyond the Standard Model: Limits from BBN and the CMB Independently and Combined

We present new Big Bang Nucleosynthesis (BBN) limits on the cosmic expansion rate or relativistic energy density, quantified via the number N_ν of equivalent neutrino species. We use the latest light element observations, neutron mean lifetime, and update our evaluation for the nuclear rates d + d → ³He + n and d + d → ³H + p. Combining this result with the independent constraints from the cosmic microwave background (CMB) yields tight limits on new physics that perturbs N_ν and the baryon-to-photon ratio η prior to cosmic nucleosynthesis: a joint BBN+CMB analysis gives N_ν = 2.898 ± 0.141, resulting in N_ν < 3.180 at 2σ. The strength of the independent BBN and CMB constraints now opens a new window: we can search for limits on potential changes in N_ν and/or η between the two epochs. The present data place strong constraints on the allowed changes in N_ν between BBN and CMB decoupling; for example, we find -0.708 < N_ν^CMB-N_ν^BBN < 0.328 in the case where η and the primordial helium mass fraction Y_p are unchanged between the two epochs; we also give limits on the allowed variations in η or in (η, N_ν) jointly. We discuss scenarios in which such changes could occur. Looking to the future, we forecast the tightened precision for N_ν arising from both CMB Stage 4 measurements as well as improvements in astronomical ⁴He measurements. We find that CMB-S4 combined with present BBN and light element observation precision can give σ(N_ν) ≅ 0.03. Such future precision would reveal the expected effect of neutrino heating (N_eff - 3 = 0.044) of the CMB during BBN, and would be near the level to reveal any particle species ever in thermal equilibrium with the standard model.   

Brownian Axion-like Particles in the Cosmic Microwave Background

We studied the non-equilibrium dynamics of an axion-like particle (ALP) weakly coupled to a thermal bath and misaligned initial conditions. The ALP's evolution is studied to leading order in the ALP coupling to the bath but to all orders in couplings among the bath's degrees of freedom. Results are obtained using both Langevin equation derived from in-in formalism and quantum master equation, where consistencies and discrepancies of the two methods are identified and discussed. A quantum fluctuation-dissipation relation is revealed in in-in formalism. The solution exhibits damping of the misaligned condensate and thermalization with the bath. It describes a mixed dark matter scenario where the initial (cold) component decays and the thermalized (hot) component grows. ALP-photon coupling is calculated explicitly as a specific example, in which we found an enhancement to ALP's relaxation rate, a potential inverted phase transition, and the requirement of higher order derivative terms. The back reaction of ALP to the photon bath is also investigated. Due to the special coupling form gaE·B, a nonzero Chern-Simons density exists and may leave observational imprints on the CMB spectrum.   

A standard model inflationary mechanism

 

A novel combination of standard model physics is shown sufficient to initiate the inflation era of the early universe[1]. It need only be assumed that quantum transitions occur within a single Planck time and that the initial singularity scaled with the Planck length. Conservation laws then initiate an inflationary result as the Pauli exclusion principle forces, at a minimum, that all conserved fermions initially have a quantum transition into adjacent locations in a Planck time. Subsequent matter-antimatter equilibria creates additional “unconserved” fermions which likewise have to transition to adjacent locations exacerbating inflation in a chain reaction fashion until a much later date when attractive forces are able to begin attenuating the runaway expansion.

The Non-Local VacuumA Framework for New Physics

This presentation describes a model of cosmology that:  automatically eliminates the cosmological constant problem; provides a framework for new physics to resolve the measured H₀ tension; predicts the existence of cosmic inflation with an e-fold volume expansion, N, of about 61; and, makes room for a non-local physical reality as the seat of quantum entanglement. The basic framework of this model is that the big bang singularity represents the opening up of a white hole whose interior is non-local vacuum that expands as the event horizon expands. In this framework it is the quantized event horizon (the vacuum horizon) that is the actual source of spacetime (gravity) and matter/energy and not the singularity or original Planck region. The horizon expansion parameters are derived using the Holographic Principle, the Schwarzchild solution, the published data on the total amount of information/entropy in the observable (local) universe (S ≈ 5x10¹⁰⁴ bits) and the assumption that the virtual energy density of the vacuum ρ_vac ≈ ρ_crit. This derivation requires there to be ≈ 4x10¹⁶ Planck sized entangled qubits in the non-local vacuum for every bit of the horizon (local reality). This ensemble of qubits has a Schwarzchild volume of ∼ 10⁻⁷⁸m³ leading to the prediction of N ≈ 61. The assumption of ρ_vac = ρ_crit leads to a prediction of the Hubble constant that is within 0.7σ of the Planck collaboration measurement. The model value for H₀ agrees perfectly with the SH0ES team measurement with the assumption that ρ_vac = 1.19 ± 0.05ρ_crit.

    

Unification of Gravity (Variational Interaction) and Electromagnetism (Flow Generated Interaction) in Universal Mechanics

In this APS April meeting, I am presenting a breakthrough which is waiting from almost 100 years in theoretical physics. In this unification process of these two interactions gravity and electromagnetism, at first I am specifying these two fundamental interactions in universal mechanical terms Respectively variational interactions and flow generated interactions. Variational interactions are generated due to variation into density of scalar field. Gravitational force is also generated due to variation into density of scalar field around bodies. So, Gravity can be classified inform of variational interactions Which are applied on each and every type of body they exist in universe. Flow generated interactions are generated due to difference between flow velocity of scalar field and velocity of object. EM like force is also generated Due to difference between flow velocities of bodies. So, EM like interactions can be classified in form of flow generated interactions, which are applied on each and every type of body they exist in universe.

After this classification, we will easily unify both variational and flow generated interactions with help of my two principles- ‘Principle of Central System Relativity’ and Principle of Physical Perception.