1 Effects of Strings in Inflation and Reheating Andrew Frey CalTech With Anupam Mazumdar and Robert Myers hep-th/0506???

2 Outline ● Motivation ● Review of String Embedding of Inflation ● Hubble-scale String Tensions ● Reheating of SM Sector ● Long Open String Phase ● Signatures of Strings? Please ask questions!

3 Motivation ● New physics at scale M affects inflation ● Usual compactifications give small signal ● Warping can lower scales More hopeful! Kaloper et al Martin & Brandenberger etc Or greater? Randall & Sundrum DeWolfe & Giddings Cosmic F-Strings? Copeland, Myers, & Polchinski Dvali & Tye

4 ● Novel string compactifications (since 2000) Naturally warped Moduli frozen Braneworld SM ● Playground for stringy inflation Inflation fits well Relate strings to cosmology Interesting effects for reheating also Giddings, Kachru, & Polchinski Kachru, Kallosh, Linde, & Trivedi... Landscape issues... Burgess et al. Jones, Stoica, & Tye... KKLMMT...

5 Brane Inflation Review Ground State Compactification ● Built on Calabi-Yau manifold ● Large warping near singularities ● Localized modes have light masses SM branes strings KK modes modulus SM throat

6 Brane Inflation ● Inflaton is brane/antibrane separation ● Potential set by brane tension ● Effective string scale high Good for EFT, bad for string signals Supergravity eta problem, finetuning? KKLMMT,... Inflationary throat Hybrid inflation Reheating from annihilation

7 Hubble-scale String Tensions A Problem with Inflation ● Tension between SM string scale and Hubble With significant warping ● Breakdown of 4D EFT Large Curvatures String Creation Super-Hagedorn Strings SM throat Model builders take care!

8 A Resolution from EFT ● Look for a story consistent with 4D EFT ● SM throat must be shorter ● Consider light scalar during inflation Cross-couplings induce mass Generic in SUGRA Dine, Randall, & Thomas Dvali earlier authors Initially in inflationary state!

9 ● Hubble-induced masses more generic even Consider self-interaction Effective mass term During inflation Consistent solution

10 Ten Dimensional Interpretation ● Fluctuations in modulus, KK modes, etc., naturally lift warp factor ● Mass increases mean warp factor greater ● Masses scale proportionately Consistent with effective field theory But also potentially visible corrections

11 Reheating the SM Sector Energy from Inflationary Sector ● Brane annihilation creates closed strings ● Closed strings decay to KK gravitons ● Energy transfer to SM throat ● Reconnection to SM branes Barnaby, Burgess, & Cline Inflationary throat SM throat Cosmic strings

12 ● Brane/antibrane annihilation ● Closed string decay ● Inflationary sector to SM sector Lambert, Liu, & Maldacena Sen... Jackson, Jones, & Polchinski Other authors Inflationary throat SM throat Time for superposition to appear in SM throat Langfelder, Myers, & Thomson (work in progress) Dimopoulos et al. Tunneling of localized modes ● Exciting SM branes ● Total reheating rate Preheating? Diakonos, Saridakis, & Tetradis Seahra Excitation of string modes

13 Reheating from SM Throat Modulus ● SM throat settles to ground state Nonstandard cosmology (10D dynamics) ● Modulus preheats while oscillating ● Thermalization later Possibly last stage ● Of course, oversimplication ● Most likely Hagedorn phase

14 Long Open String Decays ● Longitudinally polarized can split ● Transversely polarized radiate from endpoints ● Polarization determined by length Classical deviation vs. quantum fuzziness Longitudinal Transverse Balasubramanian & Klebanov Included in equilibrium (For typical parameters) Open Strings in Cosmology

15 Equilibrium vs Non-Equilibrium Open String Thermodynamics ● Distribution by length ● Average length ● Pressure ● Equilibration rate Gravitational modification?? Abel et al. Lee & Thorlacius... Lee & Thorlacius Jackson, Jones, & Polchinski Gas of branes ● Extent in compact dimensions Jackson, Jones, & Polchinski

16 ● Contrast with cosmic (closed) strings No intermediate closed strings Open strings smoothly distributed Closed strings Open strings Number of strings vs. string energy

17 Cosmology of Equilibrium Open Strings ● At sufficient density, acts like matter ● Energy loss to radiation ● Linear energy transfer Signature from stiff fluid? Cobas, Osorio, & Suárez Open string density Radiation density

18 ● Dissolves into radiation when ● Early matter dominated phase decreases e-foldings ● Density fluctuations collapse Black hole MACHOS?

19 Cosmology of Non-Equlibrium Open Strings ● Could start very far from equilibrium Or freeze out during radiation domination ● Need numerical simulations Probably sensitive to string distribution ● Not likely to scale, redshift as ● But no strings longer than critical length Exotic CDM candidate? Constraints from BBN?

20 Possible Signals or Constraints ● Can have Hubble-scale strings Expect deviation from scale-invariance ● Era of nonstandard cosmology What form does it take & what signals? ● Strings in equilibrium Any way to get a signal of strings? MACHOS from matter domination Decrease of e-foldings

21 ● Nonequilibrium string phase Remnant open strings possible Need numerical simulations ● Gravitational waves? Something else? I am very open to discussions!