Interacting Dark Energy Xinmin Zhang Institute of High Energy Physics Beijing June 18, 2004

  * Recent years Cosmology made big progress   * 4%: Particles in the standard model but why no antimatter? * Understanding the Dark Sector: Challenges to particle physics Dark Matter: Favored candidates: Axion Neutralino Thermal Production & Non-thermal Production For ex: consider a model with extra UB-L(1) UB-L(1) broken neutrino masses & cosmic string String loop decay Jeannerot, Brandenberger &Zhang, Jan. 1999

Thermal production Non-thermal 1， 2, enhancing the parameter space 3, cold dark matter warm dark matter Weak interactions “stronger” interactions

CDM: “Nagging Problems” Prediction of cuspy dark halos Apparent prediction of too much substructures thermal Non-thermal Astrophysical explanations Lin, Huang, Zhang & Brandenberger, Particle physics PRL (2001)

Dark Energy: * Negative pressure:  * Smoothly distributed, (almost ) not clustering Candidates: * Cosmological constant (or vacuum Energy) But: , cosmological problem! * Dynamical Field: Quintessence, K-essence, Phantom etc

Outline of this talk on Interacting DE Very briefly review on the current constraints on Dark Energy A model of unifying and In the framework of Quintessence, introducing coupling: A model of neutrinos with varying masses Since the scale of DE, Only comparable with mν, interesting to speculate on the possible connection betweens the two: Interaction between the neutrino and DE: A model of DE and DM: SUSY fermionic partner of Quintessence,Quintessino as DM particle Summary (Feng, Wang and Zhang) (Li, Feng Wang and Zhang) (Gu, Wang and Zhang) (Bi, Li and Zhang)

Constraints on the Dark Energy A quantity characterizing the property of Dark Energy: Equation of state: w(Z)=P/ρ For example : * Vacuum Energy: w=-1 * Quintessence: * Phantom: Model independent analysis with the following parameterization： 1，w(z)=w_0 + w_1* z 2，w(z)=w_1 + w_a*z/(1+z) (E.Linder) Using the recent 157 Supernova data published by Riess et al. astro-ph/0402512) * Within 2 σ, the cosmological constant fits well the data * Data mildly favors a running of the W across -1

Feng, Wang & Zhang Astro-ph/0404224 Huterer & Cooray Astro-ph/0404062

If the running of w(Z), especially a transition across –1, confirmed in the future, big challenge to the model building * Vacuum : w=-1 * Quintessence: * Phantom: A new scenanio of Dark Energy : Quintom (Zhang et al.) For ex: single scalar: multi-scalar:

* Interacting with neutrinos: mass varying neutrino Interacting Quintessence * If Quintessence –like scalar field responsible for the current acceleration of the Universe ,expected also to interact with the matter directly. Open new possibilities for the detection. * Direct coupling with ordinary matter Constraint from the limits on the long-range force * Interaction with derivative Goldstone theorem: Spin-dependent force a unified model of DE and Baryo(Lepto)genesis Quintessino as DM * Interacting with DM (Peebles et al ) * Interacting with neutrinos: mass varying neutrino

Quintessential Baryogenesis M.Li, X.Wang, B.Feng, X. Zhang PRD65,103511 (2002); M.Li & X. Zhang， PLB573,20 (2003) In thermo equilibrium  Cohen & Kaplan The value of depends on the model of Quintessence

If B-violation is due to electroweak sphalerons TD about 100 GeV model： Albrecht & Skordis PRL84,2076(2000) Solution: Tracking Decoupling T： If B-violation is due to electroweak sphalerons TD about 100 GeV requires

Quintessential leptogenesis & neutrino mass limits Similarly: TD determined by where which gives and for degenerate neutrino masses: defining Cosmological limits give WMAP: SDSS:

Minimal model of Baryogenesis * In the Quintessence as Dark Energy scenario, this is the minimal model for Baryogenesis in the sense that no extra particle beyond the standard model is introduced . * In ΛCDM model, with f(R): function of Ricci scalar, If , Einstein equation give: so, in radiation dominant Universe, We propose , so generating nB/s naturally! Davoudiasl,Kitano,Kribs Murayama and Steinhardt H.Li, M.Li,X.Zhang

Mass varying Neutrinos Motivations: smaller than any scale in the particle Physics, however comparable with neutrino masses Any connection between the two? Neutrino interacting with the Dark Energy In the Quintessence-like models for Dark Energy: Possible couplings: Or in the see-saw model: Implication for Leptogenesis!

Where, Corresponding the formula for the neutrino mass upper limit now is: Where,

Including the back reaction Bi,Feng,Li,and Zhang, in preparation R.Fordon, A.Nelson and N. Weiner consider a case with δ, c=0 R. D. Peccei hep-ph/0404277

Quintessino As Dark Matter If susying the Quintessence: Quintessence: Q Squintessence: σq Quintessino: (X. Bi, M. Li and Zhang) Similar to : Axion, Saxion, Axino Majoron, Smajoron, Majorino (R. Mohapatra and Zhang) If is lighter than , could serve as Dark matter Susying the following interaction (H: SU(2) doublet) gives gives * Prediction: long-lived charged particle:

Summary Dark Energy Interaction with I. for Baryo(Lepto)genesis II. neutrino: mass varying Implication in Leptogenesis Cosmological limits needs check III. SUSY: Quintessino as Dark matter (Bi, Gu, Wang and Zhang) The Dynamics of the Dark sector might be very rich! ( remember that for the 4% sector, the dynamics is already very rich)

Thanks !