Ultrafast effective multilevel atom method for primordial hydrogen recombination

Journal Article · Wed Sep 15 04:00:00 EDT 2010 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.82.063521· OSTI ID:21421128

Ali-Haiemoud, Yacine; Hirata, Christopher M ^[1]

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1. California Institute of Technology, Mail Code 350-17, Pasadena, California 91125 (United States)

Cosmological hydrogen recombination has recently been the subject of renewed attention because of its importance for predicting the power spectrum of cosmic microwave background anisotropies. It has become clear that it is necessary to account for a large number n > or approx. 100 of energy shells of the hydrogen atom, separately following the angular momentum substates in order to obtain sufficiently accurate recombination histories. However, the multilevel atom codes that follow the populations of all these levels are computationally expensive, limiting recent analyses to only a few points in parameter space. In this paper, we present a new method for solving the multilevel atom recombination problem, which splits the problem into a computationally expensive atomic physics component that is independent of the cosmology and an ultrafast cosmological evolution component. The atomic physics component follows the network of bound-bound and bound-free transitions among excited states and computes the resulting effective transition rates for the small set of 'interface' states radiatively connected to the ground state. The cosmological evolution component only follows the populations of the interface states. By pretabulating the effective rates, we can reduce the recurring cost of multilevel atom calculations by more than 5 orders of magnitude. The resulting code is fast enough for inclusion in Markov chain Monte Carlo parameter estimation algorithms. It does not yet include the radiative transfer or high-n two-photon processes considered in some recent papers. Further work on analytic treatments for these effects will be required in order to produce a recombination code usable for Planck data analysis.

• OSTI ID: 21421128
• Journal Information: Physical Review. D, Particles Fields, Journal Name: Physical Review. D, Particles Fields Journal Issue: 6 Vol. 82; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

74 ATOMIC AND MOLECULAR PHYSICS
ALGORITHMS
ANGULAR MOMENTUM
ANISOTROPY
ATOMIC PHYSICS
ATOMS
CALCULATION METHODS
COSMOLOGY
DATA ANALYSIS
ELECTROMAGNETIC RADIATION
ELEMENTS
ENERGY LEVELS
ENERGY TRANSFER
ENERGY-LEVEL TRANSITIONS
EXCITED STATES
GROUND STATES
HEAT TRANSFER
HYDROGEN
INTERFACES
MARKOV PROCESS
MATHEMATICAL LOGIC
MICROWAVE RADIATION
MONTE CARLO METHOD
MULTI-PHOTON PROCESSES
NONMETALS
PHYSICS
RADIANT HEAT TRANSFER
RADIATIONS
RECOMBINATION
RELICT RADIATION
SPECTRA
STOCHASTIC PROCESSES