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TimestampQuestion to which lecture ?LecturerYour nameYour question on the lectureAnswers
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8/7/2014 9:47:578/7 (Thursday) Structure Formation (I)Abel, TomPilloni,AlessandroHow can we interpret dark matter behaviour in Abell Clusters, and are we able to simulate such collisions?
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8/7/2014 13:43:578/7 (Thursday) Structure Formation (I)Abel, TomKwa, AnnaYou mentioned briefly that there are a lot of people studying star formation in these simulations- are star formation histories in galaxies are relevant to studying dark matter? (Are people more interested in looking at star formation in simulations because they care about the astrophysics of galaxy formation, or are there also implications for the particle nature of dark matter?)
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8/7/2014 15:03:478/7 (Thursday) Structure Formation (I)Abel, TomDo DM simulations use a retarded potential to deal with the gravity of particles separated by supra-horizon distances?
Can you say more about whether NFW profiles are an artifact of using large, discretized particles to represent the DM?
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8/4/2014 11:27:348/4 (Monday) Cosmology Basics (I)Dodelson, ScottThe slides on Quintessence are missing from the indico download. Also, could you upload your slides in pdf please?done
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8/4/2014 15:35:388/4 (Monday) Cosmology Basics (II)Dodelson, ScottLiem, SebastianWhen discussing the thermal history of the universe, you showed the density components of the universe as a function of time (a). We saw that the universe was initially radiation dominated, then matter dominated. and in the future it will be dark energy dominated.

However, today we don't have a single component dominating. We have a mixture of dark energy and matter components of the same order of magnitude. My question is how special is this? I.e. how likely is it that we happen to live in such transitionary period?

Are there models of dark energy where we don't have this coincident?		I responded to this at the beginning of the 3rd lecture. I agree that this coincidence problem is a big issue. A nice idea to address this [I'm biased!] is astro-ph/0002360
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8/5/2014 0:38:448/4 (Monday) Cosmology Basics (I)Dodelson, ScottWhat is the relation between quintessence and inflation?None that we know of. It would be great to find one. But the energy scales are extremely different so that is the challenge. More philosophically, you might counter the cynics who argue that acceleration today is definitely driven by Lambda by pointing out that observers at the time of inflation who said the same thing [I know there were no observers, but humor me] were very wrong. The "vacuum energy" in that case went away.
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8/5/2014 9:42:198/5 (Tuesday) Cosmology Basics (III)Dodelson, ScottLorshbough, DustinYou mentioned that inflationary perturbations become squeezed as they exit the horizon.

1. How do I see that squeezed states lead to a classical-to-quantum transition? In particular, by classical do you mean that the one point function is non-vanishing?

i.e.
\hat{\phi} = \phi_{classical} + \hat{\delta \phi}
so <\hat{\phi}> = \phi_{classical}

2. You stated that the perturbation mode function is constant on superhorizon scales (i.e. the oscillatory exponential becomes real leading to a constant solution and a decaying solution). Why is this related to the squeezed state story?

In particular, the states becomes squeezed (generates a non-zero Bogoliubov beta) during evolution in de Sitter whether I am superhorizon or not since all that is required is a time dependent Hamiltonian. Since the squeeze parameter r_k is related to the amplitude of the Bogoliubov beta_k, I only require a long duration of evolution in de Sitter to obtain a squeezed state with large squeeze parameter.

Thank you.		Sounds like you know more about squeezed states than I do. I quite liked Andy Albrecht's explanation of this [ astro-ph/9303001 ]. I agree that the fact that the functions are constant on large scales is independent of the squeezed state point.
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8/5/2014 12:08:068/4 (Monday) Cosmology Basics (I)Dodelson, ScottMarcus EbertYou mention at the beginning that k/a^2 would only be in there if the universe wouldn't be flat. But since it's flat this term in H^2 is 0 and we can calculate the critical energy density. This one is later used to calculate Omega _baryon and Omega_DarkMatter and the conclusion is made that since everything doesn't add up to 1 there must be something left, called Dark Energy - but this is only true if the universe is flat.
But how well do we know that the universe on very large scale is really flat and how is this information obtained from experiments? Would it matter for this conclusions that we can obtain information only from a part of the universe (where light have had already a chance to travel to us since the decoupling of matter and photons or since inflation), like we can see on Earth on small scale that everything looks flat but isn't true on large scale/whole Earth?
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8/5/2014 14:27:498/4 (Monday) Cosmology Basics (II)Dodelson, ScottWhy is the entropy density constant (does not dilute with expansion)?An rough answer is that entropy times a^3 counts particles and all interactions of interest do not change the number of particles. A more careful derivation is given in textbooks; in my book it's on pages 49-50
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8/5/2014 15:17:068/5 (Tuesday) Cosmology Basics (III)Dodelson, ScottWhen talking about inflation, you showed that comoving Hubble radius decreases with t if and only if that a double dot is positive (accelerating expansion). During inflation this is true, but at late time (i.e. now), our universe is still expanding acceleratingly, but the comoving Hubble radius increases with time?

Yes, today as well, since the universe is accelerating, \dot a is increasing, so 1/\dot a = 1/aH is decreasing
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8/4/2014 9:59:188/4 (Monday) Dark Matter and Why we Believe in it ?Finkbeiner, DouglasNewbieWhat does the:

proportional to: 1/<sigma nu> equation relate to? You went quite fast.
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8/5/2014 2:10:188/4 (Monday) Dark Matter and Why we Believe in it ?Finkbeiner, DouglasCHEUNG, CHUN HUNGThere is. prediction. for. another kind. of. interaction force exist. Do. there. any. persuative reason to support this?

I am thinking. of. possibility. to. figure. out. a. model base on. number theory. approach. This is. guided. by. intuition. on. nuclear. fission of a proton. hit. on a nucleus. resulting. with three protons, and this.continue in term of. each proton. produced. Thus the no. of. protons. exited. should. have. some relation with number 3,let say. However, it should not. be. so. simple. So, I am. thinking. to start.at. some. way. This. may be. ther stable material produced, or. some. particle. reaction type that. favour the. modling.

I. am. not sure what. to. do then. But what. I find. I may. get. some. boundage of. the. richnessat of. something at the. end. By. making. comparision. with data. of our. present universe, may. be I. will get. some. hints. to. uncover certain. type. of. dark. matter. or. some. physical. law. etc.

Do you. have any. suggestion on. this. approach ? Please. make some comments if any.
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8/6/2014 1:43:358/4 (Monday) Dark Matter and Why we Believe in it ?Finkbeiner, DouglasCHEUNG, CHUN HUNGCan. you. all. post. your response. for submitted questions here too?

Posting summery. for. discussion. .here. is welcome. too.

Thanks.
This Q&A zone is for registered participants only. Please do not post further questions here. --- SSI organizer
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8/7/2014 14:14:498/4 (Monday) Dark Matter and Why we Believe in it ?Finkbeiner, DouglasDavis, AdamWhat sets the initial point on the "freeze out" diagram for the particle dark matter model?The usual equillibrium calculation. It is a good approximation that the number density of WIMP DM is about the same as the number density of photons at early times (when kT >> M_DM)
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8/7/2014 12:08:408/7 (Thursday) Astrophysical Constraints on Dark Matter (I) Strigari, LouisBanik, NilanjanDo we understand why there is such a high dark matter content in the dSphs?
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8/7/2014 14:57:168/7 (Thursday) Astrophysical Constraints on Dark Matter (I) Strigari, LouisNiblaeus, CarlWhat is the difference (if any) between the "too big to fail" and the "missing satellites" problems? (This question is really aimed at several lecturers, in particular both Tom and Louis)
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8/5/2014 8:41:388/5 (Tuesday) Search for Dark Matter at the LHC (I)Whiteson, DanielCHEUNG, CHUN HUNGDoes the finite life time of W play any role in. the. design of experiment.? Or there. is any.important physical meaning behind? Can. you. share. your. view or. experience?No, the W lifetime is effectively zero compared to our resolution.
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8/5/2014 15:12:228/5 (Tuesday) Search for Dark Matter at the LHC (I)Whiteson, DanielYesterday there was a lot of talk on B factories. Why are B factories good for New Physics explorations? And how do LHCb results tell us about DM?

B factories look for heavy particles in loops. See Frank Porter's talk about DM searches.
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8/5/2014 15:32:088/5 (Tuesday) Search for Dark Matter at the LHC (I)Whiteson, DanielWhen is the ATLAS 8 TeV monojet paper coming out?We hope this fall!
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8/5/2014 15:36:348/5 (Tuesday) Search for Dark Matter at the LHC (I)Whiteson, DanielSince not everyone has a particle physics background, would it be possible for you or someone else to give a brief introduction to Feynman diagrams? Thanks!https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&es_th=1&ie=UTF-8#q=introduction%20to%20feynman%20diagrams
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8/6/2014 10:54:358/6 (Wednesday) Search for Dark Matter at the LHC (II)Whiteson, DanielHasterok, ConstanzeHow efficient ist the search algorithm that searches for sub-jets in one big jet and what is its working principle? Isn't it quite difficult to separate the jets since the signal in the calorimeter is quite wide due to cascades?It is quite efficient, but it's always a question of balancing signal efficiency with background rejection. The principle is to look for jets which have two sub-cores of energy deposits (like W->jj) rather than a single central deposit.
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8/6/2014 15:09:498/6 (Wednesday) Search for Dark Matter at the LHC (II)Whiteson, DanielIt seems the slide for mono-top and t-tbar is missing. Could you please update the slide online? Mono-ttbar:
https://cds.cern.ch/record/1697173?ln=en

Mono-top
https://cds.cern.ch/record/1668115?ln=en
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8/5/2014 20:39:028/5 (Tuesday) Particle Dark Matter (I)Zurek, KathrynSlidelessIf you could please put up the pdf's of your lecture before tomorrow, that'd be great. Thanks!Done. All 3 lectures under Lecture (I)
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8/5/2014 21:18:188/5 (Tuesday) Particle Dark Matter (I)Zurek, KathrynYou mentioned the Bullet Cluster in your motivating slides, something an earlier lecturer warned against, since other clusters exhibit lag in the displacement of the mass concentration. What is your take on this? (How firm does the Bullet Cluster stand in your opinion as unequivocal evidence for dark matter?)By itself, I do not think the bullet cluster is in any way conclusive evidence for dark matter, for precisely the reasons you state. Taken in conjunction with the cosmological evidence, however, it is a supporting, though not conclusive, piece of evidence.
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8/6/2014 11:45:078/6 (Wednesday) Particle Dark Matter (II)Zurek, KathrynYou mentioned direct detection of higgs interacting dark matter 'below the higgs pole', what does this mean?"Higgs pole" in this context really just means "Higgs particle"
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8/6/2014 12:25:158/6 (Wednesday) Particle Dark Matter (III)Zurek, KathrynDo you recall the reference for the LHS plot on slide 93 (on main sequence evolution disruption by ADM)? It is in neither of the listed papers on that slide.
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8/6/2014 14:22:358/6 (Wednesday) Particle Dark Matter (III)Zurek, KathrynAnswer to previous question:

http://arxiv.org/abs/1201.5387
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8/7/2014 8:51:198/6 (Wednesday) Particle Dark Matter (III)Zurek, KathrynCaputo, ReginaFirst, Thanks Kathryn for the really great lectures! My question relates to the interaction between the dark matter and the Higgs. I'd naively assume that since dark matter has mass, it must interact with the Higgs field - and then have some coupling to the Higgs boson (even if it doesn't interact with other SM particles/fields). So for my questions: Is this assumption true? If this assumption isn't true, how would DM get out of having to couple to the Higgs? Thanks again!For dark matter particles that interact with the Higgs boson (i.e. they carry SU(2) charges), interactions with the Higgs does have important effects on the mass spectra. However, this is not the only source for dark matter particle mass. For example, "SUSY breaking" mass terms also impact strongly the dark matter mass. In addition, there may be other scalars (besides the Higgs) that give particles mass.
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