Magnetic field amplification in f(R) theories of gravitylibrary/Mohanty_S_1475_08_abst.pdf2 INFN,...
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JCAP07(2008)019 ournal of Cosmology and Astroparticle Physics An IOP and SISSA journal J Magnetic field amplification in f (R) theories of gravity G Lambiase 1,2 , S Mohanty 3 and G Scarpetta 1,2 1 Department of Physics, University of Salerno, 84081-Baronissi, Italy 2 INFN, Sezione di Napoli, Italy 3 Physical Research Laboratory, Ahmedabad 380009, India E-mail: [email protected], [email protected] and [email protected] Received 8 May 2008 Accepted 1 July 2008 Published 25 July 2008 Online at stacks.iop.org/JCAP/2008/i=07/a=019 doi:10.1088/1475-7516/2008/07/019 Abstract. The inflationary amplification of magnetic field seeds for galaxies is discussed in the framework of the f (R) theories of gravity, where f (R) is of the form f (R) ∼ R n . The breaking of the conformal invariance necessary for the seeding of the primordial magnetic field from the vacuum is generated by means of the coupling of the electromagnetic field with curvature terms. We analyze the coupling of the electromagnetic field with the Riemann tensor, F αβ F α β R αβα β . We find that amplification of the magnetic field occurs during the reheating phase of evolution of the Universe. Estimates of the index n are derived by using the observed strength of the galactic magnetic fields. Moreover, the coupling of the electromagnetic field with a generic function of the scalar curvature, i.e. R m F αβ F αβ , is discussed. In this case, we find that a growing of the primordial magnetic field during the reheating epoch may occur for an appropriate choice of the powers m and n. Keywords: magnetic fields, physics of the early universe c 2008 IOP Publishing Ltd and SISSA 1475-7516/08/07019+24$30.00
Transcript of Magnetic field amplification in f(R) theories of gravitylibrary/Mohanty_S_1475_08_abst.pdf2 INFN,...
JCA
P07(2008)019
ournal of Cosmology and Astroparticle PhysicsAn IOP and SISSA journalJ
Magnetic field amplification in f(R)theories of gravity
G Lambiase1,2, S Mohanty3 and G Scarpetta1,2
1 Department of Physics, University of Salerno, 84081-Baronissi, Italy2 INFN, Sezione di Napoli, Italy3 Physical Research Laboratory, Ahmedabad 380009, IndiaE-mail: [email protected], [email protected] and [email protected]
Received 8 May 2008Accepted 1 July 2008Published 25 July 2008
Online at stacks.iop.org/JCAP/2008/i=07/a=019doi:10.1088/1475-7516/2008/07/019
Abstract. The inflationary amplification of magnetic field seeds for galaxiesis discussed in the framework of the f(R) theories of gravity, where f(R) isof the form f(R) ∼ Rn. The breaking of the conformal invariance necessaryfor the seeding of the primordial magnetic field from the vacuum is generatedby means of the coupling of the electromagnetic field with curvature terms.We analyze the coupling of the electromagnetic field with the Riemann tensor,FαβFα′β′
Rαβα′β′ . We find that amplification of the magnetic field occurs duringthe reheating phase of evolution of the Universe. Estimates of the index n arederived by using the observed strength of the galactic magnetic fields. Moreover,the coupling of the electromagnetic field with a generic function of the scalarcurvature, i.e. RmFαβFαβ, is discussed. In this case, we find that a growingof the primordial magnetic field during the reheating epoch may occur for anappropriate choice of the powers m and n.
Keywords: magnetic fields, physics of the early universe
c©2008 IOP Publishing Ltd and SISSA 1475-7516/08/07019+24$30.00
