Archive for IUCAA

Varun Sahni on Dark Matter & Dark Energy

Posted in The Universe and Stuff with tags , , , , on June 17, 2020 by telescoper

I’m very happy to be able to share a couple of lectures by esteemed cosmologist and erstwhile co-author Varun Sahni of the Inter University Centre for Astronomy & Astrophysics (IUCAA) in Pune, India. They’re at an introductory level appropriate for a summer school so I think quite a lot of students will find them interesting and informative!

Pictures from Post-Planck Cosmology in Pune

Posted in Biographical, Books, Talks and Reviews, The Universe and Stuff with tags , , on April 20, 2018 by telescoper

Regular readers of this blog (Sid and Doris Bonkers) will know that last year I went to the Inter-University Centre for Astronomy and Astrophysics in Pune (India) for a conference on `Post-Planck Cosmology’. Well, I recently received a copy of the official conference photograph, which I thought I’d share:

There is also an online collection of pictures taken during the talks, from which I have taken the liberty of extracting this picture of me during my talk:

I think this picture has a lot of potential for a caption competition, so please feel free to suggest captions through the comments block!

Back to Blighty

Posted in Biographical, The Universe and Stuff with tags , , on October 18, 2017 by telescoper

Just a brief post today to say that I got back safe and sound last night. I was up at 4am Tuesday Pune time (which was 11.30pm Monday UK time) and finally got to bed at about 11.30pm UK time last night, so apart from about 45 minutes doze on the flight I had been awake for 24 hours. Not surprisingly, I slept in this morning!

After another white-knuckle taxi ride (with the added complication of thick fog) I got Mumbai airport in good time. The flight itself was almost empty. Not only did I get a row of seats to myself in economy class, but the two rows in front in and the two rows behind were also unoccupied. I’m not entirely sure why the flight was so underbooked – as the outbound flight was absolutely crammed – but it may be that the festival of Diwali takes place this week (on Thursday or even today in some regions). Relatively few people are probably leaving India at this time compared with the many coming home to celebrate with friends and family. It’s a nice coincidence that Monday’s announcement of simultaneous detection of gravitational waves and electromagnetic radiation came so close to the Festival of Light, traditionally celebrated with fireworks and gifts of gold!

Despite liberal helpings of wine from the drinks trolley and the ability to lie down across three seats I still didn’t really sleep. I just don’t have the knack for sleeping on planes. Still, I did get to watch the film The Imitation Game which I hadn’t seen before and thought was very good.

We arrived back on schedule without the (usually) obligatory air traffic delays around Heathrow and, the arrivals hall being empty, I was out of the airport less than half an hour after landing. That’s a bit of record for me!

Anyway, I’ve various things to catch up on now that I’m back so I’ll try to get on with them. I’ll just end by thanking my hosts at IUCAA again for their hospitality and, while I’m at it, send a Happy Diwali message in Marathi to them and anyone else celebrating at this special time:


Homes from Home in Pune

Posted in Biographical, History, The Universe and Stuff with tags , , , on October 16, 2017 by telescoper

Since I’m coming back tomorrow I thought I’d wander around this morning and take a few pictures of where I’ve been staying most of the last 10 days or so. First, this is a snap of the housing complex which contains my guest apartment.

I’m actually in the first building on the right. Here is the front door.

The faculty at both IUCAA (Pune) and TFIR (Mumbai) live in housing areas provided by their respective institutions, so they form quite a close-knit community. Some of the senior staff in IUCAA are housed just round the corner from my place.

IUCAA is on the Pune University Campus (except that it has its own entrance from the main road that runs along the Northern edge of the campus, where there is a security post. There are a few of these around the IUCAA site itself, so it is very secure and quite private. The campus is large with many tree-lined roads. At its heart, on a small hill, you can find this building:

This is (or was) the Raj Bhavan (`Government House’) and it was essentially the Governor of Maharashtra’s residence during the Monsoon season. Built in 1866, it was a sort of home-from-home when Bombay (the state capital) became too unbearable.

When I was last here in 1994, this was the Main Building of the University and was quite busy. Now, however, it seems to be disused and is in a state of some disrepair, the gardens also need a bit of love and attention. There are many new buildings around the University of Pune campus (including a modern administration block nearby). Since this building is a relic of the old colonial days it may be that it will be demolished to make way for something that better suits modern India. By the way, there’s a stone slab just next to the site of this building that displays the preamble to the Constitution of India, as adopted in 1949.

Anyway, this afternoon and evening promise to be quite busy. There is a press conference at IUCAA at 6.30pm about the gravitational waves discovery I mentioned a few days ago. There will be presentations before a viewing of the live feed from Washington DC then there’ll be a panel answering questions from the press. They’ve asked me to be on the panel, so I might appear in the India media, but as I’m leaving first thing tomorrow morning I probably won’t see any of the coverage!

Post-Planck Cosmology: Day 4

Posted in Talks and Reviews, The Universe and Stuff with tags , on October 12, 2017 by telescoper

So here we are at the end of the meeting, after a fourth and final day of wide-ranging cosmology talks. I did the first presentation at 9am. I won’t summarize my own lecture because you can find the slides here:

Here are two pictures of me in action:



After that we had, amongst others, invited talks by Subhabrata Majumdar on the eROSITA all-sky X-ray survey and Somak Raychaudhury (Director of IUCAA) on large-scale structures in the local universe, Kandu Subramanian on primordial magnetic fields and Anvar Shukurov on Probabilistic Topology and Morphology (a change to the advertised title). There were also a number of shorter talks of diverse nature mainly on the subject of large-scale structure and galaxy formation.

I have known Kandu Subramanian since I was a student at Sussex and he was a postdoc there. At that time he was working mainly on gravitational lensing. I haven’t seen him for quite a long time and was surprised to see that now his hair has gone completely white. That’s what happens to you if you work on primordial magnetic fields.

The afternoon session overran and I had an appointment for Skype call so I had to leave before the closing remarks, so let me take this opportunity to thank the conference organisers for putting together such an interesting meeting and especially for inviting me back to Pune after all this time. It has been very enjoyable.

Many of the conference guests have already left and some are leaving tomorrow. I am staying in India for a few more days, however. Tomorrow morning I’m going to Mumbai to give a talk at the Tata Institute for Fundamental Research. I have to get up early tomorrow for that trip so I think I’ll take an early night.

Post-Planck Cosmology: Day 3

Posted in The Universe and Stuff with tags , , , , on October 11, 2017 by telescoper

Before carrying on with my daily updates from this meeting on Post-Planck Cosmology I’ll just remark that this is a great venue: it has all the facilities necessary to keep a group of cosmologists happy…

At the tea break this morning I managed to find a shot that included all four of the statues in the main quadrangle too:

This morning kicked off with Roy Maartens discussing the cosmological potential of the Square Kilometre Array and other future galaxy surveys, one of his main points being the benefit of using multiple tracers to beat down some of the problems with single surveys.  The first phase of this project, SKA1,  will deliver 10 million redshifts with z<0.6. With SKA2 that will go up to 1 billion galaxies out to z<2, but many things can be done without redshifts using intensity mapping. SKA1 is some way off, but the precursor `Meerkat' consisting of 64 × 13.5 metre dishes will be hopefully starting next year in South Africa.

We then had a series of talks about reionization and the formation of the first stars, an epoch usually referred to as `Cosmic Dawn' or `First Light', taking us into lunch.

In the afternoon we had talks loosely grouped around the theme of `classical cosmology' – using geometric or other probes to study the expansion history of the Universe. This session included a talk by Chris Messenger of the LIGO collaboration about the beginnings of gravitational wave cosmology, though as the current generation of detectors is only sensitive to relatively nearby sources for the time being the main effort will be devoted to distance scale measurements, attempting to measure the Hubble constant directly without the need for the traditional distance ladder.

The last part of the day was devoted to a panel discussion, chaired by Francois Bouchet that was interesting and wide-ranging but largely motivated by responses to Paul Steinhardt's talk last night.

Now, no conference dinner to tear me away tonight – but I do have to finish my talk, which is at 9am tomorrow – so that will have to do for now. Toodle-pip!

Post-Planck Cosmology: Day 2

Posted in The Universe and Stuff with tags , , on October 10, 2017 by telescoper

Just finished the last session of the day and it’s only half an hour before the conference dinner begins, so I’ll just do a brief summary.

The weather in Pune continues to be `interesting’:

It’s pouring down at the moment, in fact. The session I chaired started late because we had to postpone the conference photograph because of inclement weather.

Anyway, this morning’s talks were primarily about the difficulties of measuring B-mode polarization in the cosmic microwave background. Carlo Baccigalupi gave a perspective on foregrounds from Planck and Zeeshan Ahmed updated us on Keck/BICEP progress. There are no new results from the latter – we’ll have to wait for data from the extra 220 GHz channel – but Zeeshan also spoke about a proposal for the next generation ground-based experiment, glamorously named CMB-S4 – details of which can be found here.

The afternoon was largely devoted to early universe physics, including inflation. We’re only two days in to the conference but already several speakers have showed this plot (from here), which shows the extent to which current cosmological data disfavours various inflationary models:

Some are disfavoured, but clearly there are still lots of viable models! Too many!

For the final session of the day we were joined by Paul Steinhardt via Skype from the USA. He gave a very cogent and stimulating talk arguing that the prevailing paradigm (i.e. inflation) was about to be overturned. I don’t have time to do a full summary of his contribution, but you can check out a previous post about some of the issues he raised, and here’s a picture of the last slide of his presentation:

Anyway, that will have to do. The conference dinner beckons.

Post-Planck Cosmology: Day 1

Posted in The Universe and Stuff with tags , , , on October 9, 2017 by telescoper

Well, I’m just back to my guest flat from a pleasant birthday party for one of the conference organizers, Tarun Souradeep, is now in the same decade as me! I don’t have time to write about all the talks today so apologies to anyone I don’t mention by name. I also got called away to have tea with an old friend so missed the final session and consequently missed the last session. I can’t do that again tomorrow as I’m chairing the last session tomorrow (including a presentation from Paul Steinhardt via Skype).

Also, I forgot to take my camera to today’s session so here are a couple of pics that I’ve stolen without permission from the Director of IUCAA, Somak Raychaudhury showing Francois Bouchet and Jacques Delabrouille who gave the first two talks.

Here are some brief notes.

Francois Bouchet delivered an expert summary on the state of cosmology up to and including the Planck mission. He started by saying out that before the discovery of the cosmic microwave background, cosmology was a `semi-crackpot subject’ and went on to show how much the field has moved on: there are no longer any semi-crackpots in cosmology. Three particularly interesting points he made on his grand tour were: (i) that the `inflationary prediction’ that the spectral index of primordial density fluctuations is not that n=1 (which was argued for before inflation by Harrison and Zeld’dovich) but n=0.96, and that the difference between these numbers is very significant; (ii) there aren’t enough independent modes in the (2D) CMB to improve current limits on non-Gaussianity by much so we will have to use (3D) galaxy clustering data; and (iii) the apparent `tension’ in measurements of the Hubble constant is not solely a problem with the CMB (he mentioned this paper in particular.

Next up, Jacques Delabrouille spoke about future CMB space missions. Unfortunately none of the three putative missions currently on the table (LiteBIRD, CORE and PIXIE) has been selected for Phase A by the relevant space agencies. Although not officially dead, any of these will need to find international partners to proceed, and none will be launched for at least a decade. The current generation of CMB scientists will therefore probably have to rely on ground-based data for the immediate future. However, he was ambitious in the science goals for future missions: `we want to measure it all!’

We then had a series of talks about various matters, including the resurgence of interest in spectral distortions of the CMB that I blogged about recently.

Anyway, that will do for this evening. I’ll try to post about Day 2 tomorrow, though it is the conference dinner in the evening so I may not be in a fit state!

Return to IUCAA

Posted in Biographical, The Universe and Stuff with tags , on October 8, 2017 by telescoper

This afternoon I roused myself from my slumbers and took a stroll around the campus of the Inter-University Centre for Astronomy and Astrophysics (IUCAA). You can read more about IUCAA here.

I was last here in 1994, at which time I was working with Varun Sahni on a long review article for Physics Reports. We didn’t quite get it all finished during the month or so I was here then, but it was submitted the following year.

Given that was over twenty years ago it shouldn’t really be a surprise that I don’t remember the place all that well, but in fact it has changed quite considerably with lots of new buildings. I’m not staying in the guest accommodation area I was in last time, but in a new part just round the corner. I’ve got a small apartment, actually,including a kitchen but I think I’ll be eating at the refectory most of the time.

Anyway, here are some snaps of parts of the IUCAA complex I did recognize:

There are four statues in the main quadrangle which is featured in the first three pictures. These are of:  Sir Isaac Newton (seated under the tree), Albert Einstein (standing with hands in pockets); Galileo Galilei (in the robe with arms akimbo); and Aryabhata the great Indian mathematician-astronomer. It’s quite hard to get all four into one picture, even from the roof!

Anyway, there’s dinner and drinks coming up at 7.30 so that’ll do for a first post. The meeting starts tomorrow morning and I’ll try to tweet/blog about interesting bits until it finishes at the end of the week. The meeting is called Post-Planck Cosmology: Enigma, Challenges and Visions, so I’ll try tweeting with #PPCIUCAA2017 as the hashtag and see if it catches on!