CMBPol Mission Concept Study Telecon notes 1 July, 2008 Participants: Bock, Cooray, Hanany, Keating, Kogut, Meyer, Page, Ruhl Theory Workshop Report: Meyer: Two most important points for CMBPol mission study. 1. r~0.01 experimental goal makes sense because simplest but important class of inflation models are ruled out at this level even though inflation is not ruled out. More complicated models including string theory motivated models predict much lower levels. Inflation sub-group will enumerate the kinds of models which are ruled out with a non-detection of b-mode CMB anisotropy at that level. 2. Delensing in the presence of foregrounds and non-ideal instrument noise will be difficult and need more study. Hanany: Several different methods of removing the foregrounds were discussed and they each have strengths in different parts of thye foreground parameters space. A careful survey of the techniques and their relative merits is important. Cooray: Many foreground techniques have not yet been tested. Important to remember that it is not just r. isocurvature, non-gaussianity. Future mission the biggest gain for non-gausianity over Planck will be the E-modes. Kogut: All simulations focus on pixel-based methods. So far all successful foreground removal has been template based. Simulations for template removal should be carried out if only as a comparison. Meyer: It may be important to think about including more frequency bands to permit more foreground parameters. These do not need to span a larger frequency range. Sensitivity would not necessarily be compromised even if sensitivity per band is lower. Systematics Workshop Update: Recent planning telecon with topic leads. Workshop schedule is forthcoming. Registration is now open. Register soon. Technology Workshop Update: Registration open. Workshop registration will be $300 to cover the workshop costs. Payment page will be open soon. _____________________________ Comments on the notes: Eva Silverstein 7/1: On the theory summary, I have a correction: The inflation group discussed extensively the fact that it is not accurate (even approximately) to say that string theory models typically predict small r. There are different mechanisms in string theory, some of which (reviewed and discussed at the meeting) predict $r>.01$, falsifiable on this basis, and are among the simplest and most explicit constructions to date; while other concrete classes of models predict unobservably small $r$. I would be happy to send you more info, e.g. the talk slides, if it would help. (I am quibbling with the line ``More complicated models including string theory motivated models predict much lower levels," if this was meant to imply all or most string theory mechanisms.) From this side of things, CMBPol and other expts sensitive to r at the .01 level will be extremely useful in distinguishing the different mechanisms. An important feature of the theoretical science case is that in general, the subject is sensitive to quantum gravity effects because of the Lyth bound showing the field range is super-Planckian if we see B modes. Thus, strictly speaking the model building needs to be done in a framework (e.g. string theory) where these effects can be analyzed. It's a genuinely interesting (and potentially exciting) period we are entering where the microscopic theory is getting to the stage where we can make predictions based on concrete mechanisms, at the same time that the data is going to increase dramatically. Basically, we talked about the 4 most developed classes of models, two of which predict small $r$ and two $r>.01$ Of these classes, three will be eliminated by upcoming data according to the forecasts (with fnL helping along with r).