My current interests are in cosmology. With colleagues we are looking at linear and nonlinear gravitational lensing corrections caused by embedding inhomogeneities (galaxies, clusters, etc.) in otherwise homogeneous models of the universe. To find nonlinear effects such as the cosmological constant's alteration of Einstein's bending angle, we found it necessary to use GR solutions historically known as Swiss cheese models. We have discovered a relatively simple expression for computing the integrated Sachs-Wolfe effect caused by embedded lenses on the CMB. Using this theory we are able to model hot and cold spots that are associated with large voids and clusters.
"Fermat's least-time principle and the embedded transparent lens,"R. Kantowski, B. Chen, and X. Dai,Physical Review D,88(8), 083001, (2013)ADS: 2013PhRvD..88h3001K
"Effects of Kerr Strong Gravity on Quasar X-ray Microlensin,"B. Chen, X. Dai, E. Baron, & R. Kantowski,Astrophysical Journal,769, 131, (2013)ADS: 2013ApJ...769..131C
"Image Properties of Embedded Lenses,"R. Kantowski, B. Chen, and X. Dai,Phys. Rev. D,86, 043009, (2012)ADS: 2012PhRvD..86d3009K
"Gravitational lens equation for embedded lenses; magnification and ellipticity,"B. Chen, R. Kantowski, and X. Dai,Phys. Rev. D,84, 083004, (2011)ADS: 2011PhRvD..84h3004C
"Time delay in Swiss cheese gravitational lensing,"B. Chen, R. Kantowski, and X. Dai,Phys. Rev. D,82, 043005, (2010)ADS: 2010PhRvD..82d3005C
"Gravitational Lensing Corrections in Flat ΛCDM Cosmology,"R. Kantowski, B. Chen, and X. Dai,Ap.J.,718, 913, (2010)ADS: 2010ApJ...718..913K
"Distance redshift from an optical metric that includes absorption,"B. Chen and R. Kantowski,Phys. Rev. D,80, 044019, (2009)ADS: 2009PhRvD..80d4019C