TY - JOUR

T1 - Cosmic microwave background and inflation in multi-fractional spacetimes

AU - Calcagni, Gianluca

AU - Kuroyanagi, Sachiko

AU - Tsujikawa, Shinji

N1 - Funding Information:
The work of G.C. is under a Ramon y Cajal contract and is supported by the I+D grant FIS2014-54800-C2-2-P. S.K. is supported by the Career Development Project for Researchers of Allied Universities. S.T. is supported by the Grant-in-Aid for Scientific Research Fund of the JSPS Nos. 24540286, 16K05359, the MEXT KAKENHI Grant-in-Aid for Scientific Research on Innovative Areas Cosmic Acceleration (No. 15H05890) and the cooperation program between Tokyo University of Science and CSIC.

PY - 2016/8/18

Y1 - 2016/8/18

N2 - We use FIRAS and PLANCK 2015 data to place observational bounds on inflationary scenarios in multi-fractional spacetimes with q-derivatives. While a power-law expansion in the geometric time coordinate is subject to the usual constraints from the tensor-to-scalar ratio, model-independent best fits of the black-body and scalar spectra yield upper limits on the free parameters of the multi-fractal measure of the theory. When the measure describing the fractal spacetime geometry is non-oscillating, information on the CMB black-body spectrum places constraints on the theory independent from but weaker than those obtained from the Standard Model, astrophysical gravitational waves and gamma-ray bursts (GRBs). When log oscillations are included and the measure describes a discrete fractal spacetime at microscopic scales, we obtain the first observational constraints on the amplitudes of such oscillations and find, in general, strong constraints on the multi-scale geometry and on the dimension of space. These results complete the scan and reduction of the parameter space of the theory. Black-body bounds are obtained also for the theory with weighted derivatives.

AB - We use FIRAS and PLANCK 2015 data to place observational bounds on inflationary scenarios in multi-fractional spacetimes with q-derivatives. While a power-law expansion in the geometric time coordinate is subject to the usual constraints from the tensor-to-scalar ratio, model-independent best fits of the black-body and scalar spectra yield upper limits on the free parameters of the multi-fractal measure of the theory. When the measure describing the fractal spacetime geometry is non-oscillating, information on the CMB black-body spectrum places constraints on the theory independent from but weaker than those obtained from the Standard Model, astrophysical gravitational waves and gamma-ray bursts (GRBs). When log oscillations are included and the measure describes a discrete fractal spacetime at microscopic scales, we obtain the first observational constraints on the amplitudes of such oscillations and find, in general, strong constraints on the multi-scale geometry and on the dimension of space. These results complete the scan and reduction of the parameter space of the theory. Black-body bounds are obtained also for the theory with weighted derivatives.

KW - cosmological parameters from CMBR

KW - cosmology of theories beyond the SM

KW - physics of the early universe

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U2 - 10.1088/1475-7516/2016/08/039

DO - 10.1088/1475-7516/2016/08/039

M3 - Article

AN - SCOPUS:84986003693

SN - 1475-7516

VL - 2016

JO - Journal of Cosmology and Astroparticle Physics

JF - Journal of Cosmology and Astroparticle Physics

IS - 8

M1 - 039

ER -