December 28 31 2018 NCTS FuGuangShan 5 th

December 28 -31, 2018 @NCTS, Fu-Guang-Shan 5 th International Workshop on Dark Matter, Dark Energy and Matter-Antimatter Asymmetry Chameleonic Dark Matter: Implications for current and early Universe Taishi Katsuragawa (桂川 大志) 華中師範大学 (Institute of Astrophysics, CCNU) Reference 1. “Dark matter in modified gravity? ” Phys. Rev. D 95 044040 (2017) 2. “Cosmic History of Chameleonic Dark Matter in F(R) Gravity” Phys. Rev. D 97, 064037 (2018) 3. “F(R) gravity in the early Universe: Electroweak phase transition and chameleon mechanism” [ar. Xiv: 1812. 00640] In collaboration with Shinya Matsuzaki (Jilin U. ), Eibun Senaha (IBS), Hua Chen (CCNU) Taishi Katsuragawa (CCNU)

Outline of Our Research 1 of 15 Modified gravity can explain DM as well as DE? 1. Unification of Dark Side of the Universe ‒ Modified gravity is one solution to answer DE problem. ‒ Can we solve DM problem in the same framework? 2. New field from ``beyond-GR” (modification of gravity) ‒ Dynamical DE (Cosmological ``constant”→``Field”) ‒ Background to explain accelerated expansion ＋ Oscillation around background ‒ When oscillation is quantized, we obtain particle picture ‒ Particle picture of new field = New particle＝DM? 3. Interdisciplinary and challenging topic ‒ Possible solution to Coincidence Problem ‒ New application of modified gravity ‒ Study on new DM candidate 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

F(R) Gravity and Scalaron Field 2 of 15 F(R) Gravity Theory cf. ) EH-action Replace: Weyl trans. where 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Chameleon Mechanism (for dust) 3 of 15 ``Effective” mass In high-density region, eff. mass becomes large. c. f. ) matter effect for neutrinos → ``Fifth force” is screened to agree with Solar-System constraint 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Dark Matter in F(R) Gravity? 4 of 15 Scalaron Field ＝ Dynamical DE ‒ What about particle picture of scalaron? ‒ “Chameleon particle” [Burrage and Sakstein (2017)] Scalaron’s Properties (as new particle) • SM singlet and massive scalar field • Very weak coupling to SM particles • Variable mass due to chameleon mechanism What if scalaron is DM? ‒ ``Chameleonic” DM ‒ DE and DM are unified? ‒ It is nontrivial if one theory explains two problems. . . 2018/12/29 (Sat. ) DM Chameleonic Dark Matter: Implications for Current and Early Universe DE Taishi Katsuragawa (CCNU)

Strategy and Issues 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe 5 of 15 Taishi Katsuragawa (CCNU)

Matter Sector After Weyl Trans. Matter Sector exponential form Frame-difference 2018/12/29 (Sat. ) 6 of 15 Coupling to matter Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Matter Coupling 7 of 15 Scalaron universally couples with SM particles • For massless vector (Photon, Gluon) Induced by anomaly For photon For gluon • Massive scalar field (Higgs) • Massive fermion (Quarks, Leptons) • Massive vector (Weak bosons) 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

F(R) Model and Scalaron Mass GR Viable F(R) gravity model for DE [Starobinsky (2007)] 8 of 15 to cure singularity problem [Frolov (2008)] [Dev et al. (2008)] where Scalaron mass 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Stability in Late-time Universe 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe 9 of 15 Taishi Katsuragawa (CCNU)

Scalaron Mass in Current Universe 10 of 15 Scalaron mass in typical galaxies 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Scalaron Relic Density 11 of 15 DM DM 2018/12/29 (Sat. ) DE DE At present Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Cosmic Environment in Early Universe 12 of 15 Perfect Fluid Approximation Sum over all SM species NB. ) For Radiation We deal with neutrinos as radiation 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Scalaron Mass in Early Universe 13 of 15 (original) Starobinsky model Inflation experimental bound time 2018/12/29 (Sat. ) [Adelberger et. al (2006)] [Berry and Gair (2011)] Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Scalaron in EWPT BG Environment 14 of 15 Perfect fluid approx. SI-2 HDM with resum. SI-2 HDM without resum. 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Summary and Discussion 15 of 15 We studied scalaron as new DM candidate Interaction to SM particles ‒ Very weak and suppressed by Planck mass scale ‒ No thermal production (out of thermal equilibrium) Chameleonic properties ‒ Very light in current Universe, heavy in early Universe ‒ If SI is realized in early Universe, very light before EWPT Stability and Lifetime ‒ Decaying modes to SM particles ‒ Long enough to be DM candidate at late-time Relic Abundance ‒ Estimation based on coherent oscillation ‒ Potential origin of oscillation in EWPT ‒ Possibility to address the coincidence problem 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Thank you! Taishi Katsuragawa (CCNU)

17 of 15 Appendix 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Future Directions 18 of 15 There are still many mysteries to be addressed In early Universe BBN • BBN constraint? ‒ Scalaron would affect BBN ‒ BBN constraint is converted into the constraint on F(R) gravity • Stability and lifetime? In late-time Universe • Coupling b/w DM & DE? ‒ DM and DE are unified as scalaron → to arise interactions ‒ There is energy transfer in dark sector ‒ To embed into interacting DE model [Farrar and Peebles (2004)] • (In-)Direct detection (to distinguish other candidates)? and so on… 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Curvature Test of Gravity and Screening Mechanism 19 of 15 GR Screening Mechanism Modified Gravity Newton Potential 2018/12/29 (Sat. ) Screening mechanism is a key to avoid the constraints on the fifth force! Psaltis (2008) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

20 of 15 [Frolov (2008)] [Kobayashi and Maeda (2008)] [Dev et al. (2008)] Potential minimum 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Stability in Early Universe 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe 21 of 15 Taishi Katsuragawa (CCNU)

Direct Detection Environment 22 of 15 Direct Detection ‒ DM is detected by collision with nuclei. ‒ Chameleon mechanism is characterized by the property of target matter. The effective model for each experiments? ‒ Interatomic distance or density of target matter ‒ Target-matter dependence of observables ‒ Specific signal at the surface of target matter? Target matter heavy ? light Different environment 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe Taishi Katsuragawa (CCNU)

Thermal History of the Universe HOT Transition Temperature 23 of 15 Time Inflation ends Electroweak phase transition QCD phase transition Big Bang Nucleosynthesis COLD Matter-Radiation equality CMB decoupling (recombination) 2018/12/29 (Sat. ) Chameleonic Dark Matter: Implications for Current and Early Universe ~380000[yr] Taishi Katsuragawa (CCNU)