## A Plug for Some Research…

Very busy today so I just thought I’d give a bit of publicity to a paper that’s just been accepted for publication. I’m actually one of the authors, but the other guys (Dipak Munshi of Sussex, Bin Hu of Leiden, Alessandro Renzi of Rome, and Alan Heavens of ~~South Kensington Technical ~~ Imperial College) did all the work! I’m posting it mainly to remind myself that there is a world outside of administration. If it weren’t for my inestimable (STFC-funded) postdoc, Dipak Munshi, I don’t know where my research would be!

Here is the abstract:

We use the optimised skew-spectrum as well as the skew-spectra associated with the Minkowski Functionals (MFs) to test the possibility of using the cross-correlation of the Integrated Sachs-Wolfe effect (ISW) and lensing of the cosmic microwave background (CMB) radiation to detect deviations in the theory of gravity away from General Relativity (GR). We find that the although both statistics can put constraints on modified gravity, the optimised skew-spectra are especially sensitive to the parameter B

_{0}that denotes the theCompton wavelengthof the scalaron at the present epoch. We investigate three modified gravity theories, namely: the Post-Parametrised Friedmanian (PPF) formalism; the Hu-Sawicki (HS) model; and the Bertschinger-Zukin (BZ) formalism. Employing a likelihood analysis for an experimental setup similar to ESA’s Planck mission, we find that, assuming GR to be the correct model, we expect the constraints from the first two skew-spectra, S^{(0)}_{ℓ}and S^{(1)}_{ℓ}, to be the same: B_{0}<0.45 at 95 confidence level (CL), and B_{0}<0.67 at 99 CL in the BZ model. The third skew-spectrum does not give any meaningful constraint. We find that the optimal skew-spectrum provides much more powerful constraint, giving B_{0}<0.071 at 95 CL and B_{0}<0.15 at 99 CL, which is essentially identical to what can be achieved using the full bispectrum.

It’s part of a long sequence of papers emanating from work done by Dipak (with various combinations of co-authors, including myself) which have been aimed at optimising the use of statistical techniques for detecting and quantifying possible departures from the standard model of cosmology using various kinds of data; in this case the paper is entitled *Probing Modified Gravity Theories with ISW and CMB Lensing*; `ISW means the Integrated Sachs-Wolfe Effect and CMB is the cosmic microwave background. This kind of work doesn’t have the glamour of some cosmological research – I don’t think we’ll be writing a press release when it gets published! – but it is the kind of preparatory analysis that is essential if cosmologists are to make the most of present and forthcoming observational data, which is why we keep plugging away…

May 12, 2014 at 6:05 pm

In my opinion, 3-pt function, no matter bispectrum or skewness, are fruitful information carriers. Combined with spectra, 3-pt function could bring some factor improvements. More importantly, it is free, they are encoded in the map, no need to launch a new satellite or telescope.