Cosmic Strings and Superstrings宇宙字符串和超弦.ppt

Cosmic Strings and Superstrings Joseph Polchinski KITP, UC Santa Barbara Many potential cosmic strings from string compactifications: Production of cosmic strings: Brane inflation: Brane inflation: Brane inflation: Brane inflation: Brane inflation: Brane inflation produces strings: Other production mechanisms Hybrid inflation Instabilities of strings I Instabilities of strings II Instabilities of strings II Instabilities of strings II Instabilities of strings II Summary Possible signatures (gravitational!): Cosmic microwave background and galaxy formation CMB power spectrum CMB Nongaussianity CMB Polarization A cosmic string lens (CSL1)? Gravitational waves from strings String cusps Network uncertainties -- Distinguishing superstrings via interactions: Distinguishing superstrings II Conclusions Brane inflation models tend to have lower Hinf, low levels of tensor modes (e.g. r ~ 10-9 for KKLMMT). However, the strings themselves produce tensor modes, polarization might ultimately be sensitive down to Gm ~ few x 10-9 at CMBPOL (Seljak Slosar). (Polarization vs. power spectrum). Unfortunately not (higher resolution Hubble pictures): No quoted bounds from lensing. (Bounds from CMB imply d 1.2”). Cosmic strings eventually decay into gravitational waves. Interesting signal both from low harmonics of string and high.* For low harmonics, f ~ 1/length, GW energy density is f dWGW/df ~ 10-3 (Gma)1/2 (for a 50Gm, Gm 10-9). See e.g. text by Vilenkin and Shellard Note the enhancement at large a: loops red-shift like matter, so during radiation era their density is enhanced if they live longer. Current bound: f dWGW/df 4 x 10-8 (Jeter, et al. 2006, PPTA) gives Gm 2 x 10-9 for a ~ 0.1 but only Gm 2 x 10-6 for a ~ 10-4. Parkes Pulsar Timing Array should reach f dWGW/df 10-10, Gm 10-9 for a ~ 10-4 (after 10 years). Square Kilometer Array should reach f dWGW/df 10-12, covers whole brane inflation range; LISA/LIGO III reach f dWGW/df 10-11, Gm 10-11. Typically