分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-06
摘要： We investigate the influence on the inflationary predictions from the reheating processes characterized by the e-folding number N-reh and the effective equation-of-state parameter wreh during the reheating phase. For the first time, reheating processes can be constrained in the N-reh - w(reh) plane from Planck 2015. We find that for Higgs inflation with a nonminimal coupling to gravity, the predictions are insensitive to the reheating phase for current CMB measurements. We also find that the spontaneously broken SUSY inflation and axion monodromy inflation with phi(2/3) potential, which with instantaneous reheating lie outside or at the edge of the 95% confidence region in the n(s) - r plane from Planck 2015 TT, TE, EE + lowP, can well fit the data with the help of reheating processes. Future CMB experiments would put strong constraints on reheating processes.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-06
摘要： The measured masses of the Higgs boson and top quark indicate that the effective potential of the standard model either develops an unstable electroweak vacuum or stands stable all the way up to the Planck scale. In the latter case in which the top quark mass is about 2 sigma below its present central value, the Higgs boson can be the inflaton with the help of a large nonminimal coupling to curvature in four dimensions. We propose a scenario in which the Higgs boson can be the inflaton in a five-dimensional Gauss-Bonnet braneworld model to solve both the unitarity and stability problems which usually plague Higgs inflation. We find that in order for Higgs inflation to happen successfully in the Gauss-Bonnet regime, the extra dimension scale must appear roughly in the range between the TeV scale and the instability scale of standard model. At the tree level, our model can give rise to a naturally small nonminimal coupling xi similar to O(1) for the Higgs quartic coupling gamma similar to O(0.1) if the extra dimension scale lies at the TeV scale. At the loop level, the inflationary predictions at the tree level are preserved. Our model can be confronted with future experiments and observations from both particle physics and cosmology.
分类： 物理学 >> 基本粒子与场物理学 提交时间： 2016-05-06
摘要： It was shown recently that, without jeopardizing the success of the. cold dark matter model on cosmic scales, the modified Newtonian dynamics (MOND) can be derived as an emergent phenomenon when axionlike dark matter particles condense into superfluid on the galactic scales. We propose in this paper a Dirac-Born-Infeld (DBI) scalar field conformally coupled to the matter components. To maintain the success of MOND phenomenon of dark matter superfluid on the galactic scales, the fifth force introduced by the DBI scalar should be screened on the galactic scales. It turns out that the screening effect naturally leads to a simple explanation for a longstanding puzzle that the MOND critical acceleration coincides with present Hubble scale. This galactic coincidence problem is solved, provided that the screened DBI scalar also plays the role of dark energy on the cosmic scales.
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