Degenerate neutrino as a Degenerate neutrino as a Dark EnergyDark Energy

12th Marcel Grossmann Meeting, 12-18 July 2009, Paris

Hyung Won Lee, Inje UniversityJuly 15, 2009

Collaboration with K.Y. Kim, R. Ruffini

ContentsContentsIntroductionProperties of degenerate

neutrinoEvolution of density parametersPossibility as a dark energyRemarks

IntroductionIntroductionUniverse is in accelerating

expansionRiess & Perlmutter• Apparent Bolometric Magnitude m(z)

IntroductionIntroductionUniverse is in accelerating

expansionRiess & Perlmutter

IntroductionIntroductionUniverse is in accelerating

expansionRiess & Perlmutter

IntroductionIntroductionUniverse is in accelerating

expansionRiess & Perlmutter

IntroductionIntroductionThe present Universe

• accelerated expansion supernova type Ia (SN Ia) data

EOS (equation of state)

• Main issue of the present cosmology : How to explain the present accelerating universe? negative pressure : Dark Energy candidate: cosmological constant , quintessence , k- essence , holographic dark energy , phantom matter , MaVaN …

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IntroductionIntroductionAll candidates have weaknessNo physical explanation is givenCan we explain dark energy or

accelerating expansion with some physical principle?

Can we explain accelerating expansion with neutrinos?

Properties of degenerate Properties of degenerate neutrinoneutrinoDecouple at early timeEnergy density proportional to

degeneracy parameter

It may have mass

Evolution of density Evolution of density parametersparametersHubble equation

Distance modulus

CDM

GH

3

82

z

ML dzzzH

zcd

0

43

0

')'1()'1()1(

Evolution of density Evolution of density parametersparameters(0.1, 0.9), (0.3, 0.7), (0.5, 0.7),

LCDM

Possibility as a dark Possibility as a dark energyenergyLight mass : do not generate

structureMay dominate energy density

with degeneracy Evolution may different from

standard cosmology

Possibility as a dark Possibility as a dark energyenergyIt is not possible to explain with

standard considerationNeed to study carefully

Boltzmann equation

))(()( pECfL

RemarksRemarksIt seems not possible as a dark

energy except mass varying with scalar field coupling

Cosmological integration of kinematic equation