Particle Cosmology and Gravitational Theories Group at Fukushima University

 In our laboratory, we mainly study inflationary cosmology, dark energy problem and modified gravity theories.
 We investigate cosmology to construct a consistent theory of cosmic evolution from the beginning of the universe to the present time. In particular, we systematically explore the origins of (i) homogeneity, isotropy, flatness of the universe (inflation) [1, 2], (ii) large scale structure (primordial density perturbations) [3, 4], (iii) cosmic magnetic fields [5, 6], (iv) current cosmic acceleration (dark energy) [7−10], (v) matter (baryon asymmetry) [11, 12] in detail.

[1]
K. Bamba, Z. K. Guo and N. Ohta, ``Accelerating Cosmologies in the Einstein-Gauss-Bonnet Theory with Dilaton,'' Prog. Theor. Phys. 118, 879 (2007)
[arXiv:0707.4334 [hep-th]].
[2]
K. Bamba and S. D. Odintsov, ``Inflationary cosmology in modified gravity theories,'' Symmetry 7, 220 (2015)
[arXiv:1503.00442 [hep-th]].
[3]
K. Bamba and M. Yoshimura, ``Curvaton scenario in the presence of two dilatons coupled to the scalar curvature,'' Prog. Theor. Phys. 115, 269 (2006)
[hep-ph/0601047].
[4]
K. Bamba, ``Generation of large-scale magnetic fields, non-Gaussianity, and primordial gravitational waves in inflationary cosmology,'' Phys. Rev. D 91, 043509 (2015)
[arXiv:1411.4335 [astro-ph.CO]].
[5]
K. Bamba and J. Yokoyama, ``Large scale magnetic fields from inflation in dilaton electromagnetism,'' Phys. Rev. D 69, 043507 (2004)
[astro-ph/0310824].
[6]
K. Bamba and M. Sasaki, ``Large-scale magnetic fields in the inflationary universe,'' JCAP 0702, 030 (2007)
[astro-ph/0611701].
[7]
K. Bamba, S. Nojiri and S. D. Odintsov, ``The Universe future in modified gravity theories: Approaching the finite-time future singularity,'' JCAP 0810, 045 (2008)
[arXiv:0807.2575 [hep-th]].
[8]
K. Bamba, C. Q. Geng, S. Nojiri and S. D. Odintsov, ``Crossing of the phantom divide in modified gravity,'' Phys. Rev. D 79, 083014 (2009)
[arXiv:0810.4296 [hep-th]].
[9]
K. Bamba, C. Q. Geng, C. C. Lee and L. W. Luo, ``Equation of state for dark energy in $f(T)$ gravity,'' JCAP 1101, 021 (2011)
[arXiv:1011.0508 [astro-ph.CO]].
[10]
K. Bamba, S. Capozziello, S. Nojiri and S. D. Odintsov, ``Dark energy cosmology: the equivalent description via different theoretical models and cosmography tests,'' Astrophys. Space Sci. 342, 155 (2012)
[arXiv:1205.3421 [gr-qc]].
[11]
K. Bamba, ``Baryon asymmetry from hypermagnetic helicity in dilaton hypercharge electromagnetism,'' Phys. Rev. D 74, 123504 (2006)
[hep-ph/0611152].
[12]
K. Bamba, C. Q. Geng and S. H. Ho, ``Hypermagnetic Baryogenesis,'' Phys. Lett. B 664, 154 (2008)
[arXiv:0712.1523 [hep-ph]].