Saturday, 31 May 2014

Planck 2014 Liveblog: Day Five Session 4

We come finally to the last session of Planck.  The downside to a week-long conference is that I tend to suffer from burnout, so I skipped the first talk as it was another string theory inflation talk.  I return for the last two, which do look a bit more interesting.

Friday, 30 May 2014

Planck 2014 Liveblog: Day Five Session 3

We return after lunch for another session of leptonic physics.

Planck 2014 Liveblog: Day Five Session 2

We come at last to the end of the conference.  Last night was the banquet, so I regrettably missed the first session this morning.  The second morning session looks to be related to leptonic physics.

Planck 2014 Liveblog: Day Four Session 4

I had to miss the first session after lunch.  For the last parallel session of the conference, I've decided to attend the session with the very general title, "SUSY and non-SUSY phenomenology".

Thursday, 29 May 2014

Planck 2014 Liveblog: Day Four Session 2

Second plenary session of the day.  Announced that Planck next year will be in Ioannina, in NW Greece.  We are promised nice weather!  It's rained this week in Paris.

Planck 2014 Liveblog: Day Four Session 1

While I still have things on my mind, I am ready to resume my liveblog of Planck 2014.  Unfortunately I overslept this morning and so missed the first talk of the day.  It looks like we had a talk trying to put axions into models with classically scale-invariant electroweak Lagrangians.  The model involves, in addition to the axion, a pseudo-dilaton and two Higgs doublets.  The main lesson is that in such models, one must address the strong CP problem which requires ultra-weakly coupled scalars.

Wednesday, 28 May 2014

Planck 2014 Day Three

Unfortunately, I have to suspend my liveblog of Planck for today as I have other things I need to do.  Hopefully I will be able to resume tomorrow.

Planck 2014 Liveblog: Day Two Session 4

Final session of the day, I'm in the flavour and neutrinos section.

Tuesday, 27 May 2014

Planck 2014 Liveblog: Day Two Session 3

First parallel session of the conference.  I've decided to go with the session on composite Higgs.

Planck 2014 Liveblog: Day Two Session 2

Second plenary session.

Planck 2014 Liveblog: Day Two Session 1

After yesterday's talks got a bit technical, stringy and full of context-free equations for me, today's parallel sessions look more grounded in phenomenology.  Plus, we have the first parallel session after lunch, and I should be able to find some interesting talks there.

Planck 2014 Liveblog: Day One Session 4

The final session of the first day is about inflation and cosmology.  We have only two talks.

Monday, 26 May 2014

Planck 2014 Liveblog: Day One Session 3

The first post-lunch session looks like a string theory session.

Planck 2014 Liveblog: Day One Session 2

We move on to the post-coffee session, on Higgs physics.

Planck 2014 Liveblog: Day One, Session 1

As hinted in the last email, I can now blog about a conference that should hold my attention better.  Planck 2013, which opens with a solid day of plenary talks, ten in total.  The morning session involves two.

Origins of Mass 2013

So, what happened?  Well, in essence this conference turned out to be a poor fit for me, and I got bored.  It didn't help that I knew almost no one there, and that the bus drivers to get to the University were shockingly rude (seriously, the worst I have ever experienced).  So I rather lost motivation to keep writing about it.

Still, this is the chance whenever you go to a new conference.  And it gave me an excuse to go to Denmark, which I would not have done otherwise.  The conference trip to Egeskov Castle was also quite nice.

Now I'm in Paris, a city which somehow manages to live up to its daunting reputation.  I've enjoyed a weekend seeing cultural legends (the Louvre, the Champs Elysees, the Eiffel Tower, Notre Dame ...) and now I get to attend a conference that I should enjoy, Planck 2014.

Tuesday, 20 May 2014

Fun with Everyone's Favourite Figwits

Two stories I noticed today about UKIP politicians forced to apologise for saying what they really think.  First, party leader Nigel Farage backpeddles his comments about Romanian neighbours:
Nigel Farage has expressed “regret” for controversial remarks he made about Romanians, saying he was “completely tired out” during an interview.
Initially, he insisted that he stood by his words, saying that people had a "perfect right" to be concerned if a group of Romanians moved in next door.
He told BBC News: "I regret the fact that I was completely tired out and I didn't use the form of words in response that I would have liked to have used.
Personally, when I regret saying something when tired it's because it is what I actually believe, unfiltered by civility.  But that's just me.

Monday, 19 May 2014

Origins of Mass 2014: Day One, Session 3

Another odd thing about this conference is that there are more talks after lunch than before it.  This is particularly notable today, where we have five(!!) post-lunch talks keeping us here till after 6pm.  I'm strongly tempted to leave earlier than that.

1:30 pm: Do interacting UV fixed points exist, and if so, what can we do with them? Daniel Litim

I was talking to Daniel's student earlier, so I know what this talk is about: gravity.  Specifically, asymptotic safety: the possibility that GR runs to a UV interacting fixed point.  This resolves the issue of quantum gravity in an interesting way.

The title is a question, but the answer is apparently yes!

Issue goes beyond gravity, to all theories with a sickness in the UV: in particular, the Higgs and abelian gauge theories.

Fixed points: classical example is non-interacting point.  In perturbation theory, sign of beta-function encodes whether this fixed point lives in the UV or the IR.  In either case, the theory is only predictive to some point in the other regime.  e.g. QCD has UV non-interacting fixed point (is arbitrarily predictive in the UV) but not in the IR (is predictive only to around ΛQCD ~ GeV).

Interacting fixed points: arise from non-trivial zeroes in the (full) beta function.  Simple example: naively non-renormalisable coupling, has linear term in beta function with positive coefficient.  If coupling has negative coefficient for quadratic term (as for QCD) then UV interacting fixed point.  Obviously, for this to make sense, need to still be in domain of perturbation theory.  Points to either small dimensionality of coupling or large number of fields.

Examples in practice:
  1. Gravity in 2 + ε dimensions.
  2. Four-fermion couplings in 2 + ε dimensions.
  3. Gluons in 4 + ε dimensions.
All need ε very small.

New example: Strictly 4D gauge theory.  Start with walking quasi-fixed point, where beta function is very small so coupling evolves very slowly.  Take a large Nc, fixed g2Nc limit.  Now look for cancellation between quadratic and cubic terms in beta function.

Without Yukawa couplings, this is impossible: sign of cubic term is wrong.  A simple choice, with single matrix Higgs coupling to fermions and self, seems to work.  Model has one-dimension fixed point, i.e. to reach UV interacting fixed point must constrain three couplings in theory in terms of one of them.  e.g. Write Yukawa, Higgs quartic couplings in terms of gauge couplings.

Proof: UV fixed points do exist in 4D.  Can we find one for gravity?  Looking for one based on large anomalous dimension of the graviton, close to 2 so linear term in beta function becomes small.  This forces us to consider strong coupling, unlike the previous perturbative possibility.

Evidence that it might, in a power series expansion of the Ricci scalar (a simplified gravity model).

2:20 pm: From neutrino data to mass models (and back) with leptogenesis, Pasquale Di Bari

Don't be too ambitious: focus on a single cosmological problem, the matter-antimatter asymmetry.

BICEP2 may point towards interesting new era, when after inflation the temperature is so high that QCD has frozen out.

It always bothers me when speakers don't seem to realise they have a microphone.  Feedback and distortion make it harder to follow you!  Seriously, I'm losing interest already.

Cosmological limits (Planck) nearly rule out the degenerate neutrino spectrum.

Once again, there is no need to shout.

Origins of Mass 2014: Day One, Session 2

Unlike places like Planck or Pheno, this conference works with a smaller number of longer talks.  Hence, we had only one talk in the pre-break morning session and have only two more before lunch.  Also unlike most other conferences, the talks don't seem to fit any obvious pattern.

Origins of Mass 2014: Day One, Session 1

It seems that another week has passed, and I find myself at my second conference of the summer.  This is the Origins of Mass conference in Odense, hosted by CP3 Origins.  This is my first time at this conference.

Saturday, 10 May 2014

Pheno 2014 Overview

With the conference over, and having caught up on my sleep, I'll just say a few words in summary of the whole thing.

Pheno was, to me personally, fun as always.  Though the number of people I met at Tasi continues to go down, a clue that this is a conference best for graduate students, a position I move further and further from.  We saw that a few times in this conference, where I commented that certain plenary talks were a bit basic for me.  For someone who has been to none or only a few conferences, that general background was likely much more essential.

It's not as if I learned nothing from the plenary talks, either.  Martin Schmaltz's talk on the Higgs theory did a good job of covering the different attitudes towards the naturalness problem, and really helped me understand the issues with conformal symmetry ideas.  The talks from the second session on Tuesday, on dark matter and the Icecube neutrinos, were also interesting.

As for the parallel talks, we had a good selection as always.  Oddly enough, I probably enjoyed the talks on tools the most; Jamie Tattersall talking about the interesting new CheckMATE, Jamie Gainer offering a very well-written and structured talk on model-independent searches, and Joel Walker's discussion of the AEACuS software and meta-language.  Clearly, first names beginning with J are the way to go.

The banquet was in a different location to the last two years, which turned out to somehow manage to be an improvement.  I was very impressed.  Lastly, we also had a showing of Particle Fever.  While not exactly related to Pheno (except in as much as we had Nima attending), I hadn't seen the film before and did enjoy it.

Thursday, 8 May 2014

Pheno 2014 Liveblog: Day Three Session 2

We come at last to the final session of Phenomenology 2014.  Sadly, I may well not be able to stay for the whole session because I have a plane to catch.  This is especially true given that we have Nima giving the last talk, so that'll run long, and I was not able to check in to my flight online.

Wednesday, 7 May 2014

Pheno 2014 Liveblog: Day Three Session 1

We start the final day with a session on neutrino physics.

Pheno 2014 Liveblog: Day Two Session 4

The last set of parallel talks.  I'm in B Physics 2 and BSM, for reasons that are probably apparent to anyone who knows me.

Pheno 2014 Liveblog: Day Two Session 3

We return for our third set of parallel sessions.

Pheno 2014 Liveblog: Day Two Session 2

This session is about dark matter and other particle astrophysics.  Again, the post-coffee break session is more interesting to me.  I'm not sure if I should be happy or sad about this; it lets me sleep in if I need to without missing too much, but it also leaves me with less motivation to get up.  Plus, if the interesting talks came first I could skip the second session and get some work done.

Tuesday, 6 May 2014

Pheno 2014 Liveblog: Day Two, Session 1

The conference moves to its second day.  Last night was the banquet, so I missed the first talk this morning as a result.  But it was an LHCb talk, so I regret nothing.  The morning session is mostly about flavour physics, with experiment, theory and lattice.

Pheno 2014 Livebog: Day One, Session 4

The last session of the day, and the halfway point as far as parallel talks go.  This time I'm staying in a single place, the BSM Higgs session.

Pheno 2014 Liveblog: Day One, Session 3

First parallel session of the conference.  I'm going to try and switch between rooms, starting in Dark Matter 1.

Pheno 2014 Liveblog: Day One Session 2

More coffee, new session.  Now it's theory, so that might also help me stay awake.

Monday, 5 May 2014

Pheno 2014 Liveblog: Day One Session 1

It's conference time, and that means live blogs!  I'm planning to do a slightly different format to last year, with less during-talk blogging and more of a summary post for each talk.  This will minimise the amount of typing I have to do during the talks, which might annoy people sat near me!

It's the first plenary session, so that means a review of experimental (collider) results.  This is fairly straightforward, as the LHC has been shut down for a while and this isn't the place any new discoveries would be announced anyway.