1) Forums : Cosmology and Astronomy : Early galaxies (Message 22634)
Posted 8 days ago by Profile Benjamin Wandelt
Post:
Hi -
I just discovered your questions. Unfortunately I can no longer see the link of the original post.
Best,
Ben
2) Forums : Cosmology and Astronomy : Last news... (Message 22633)
Posted 8 days ago by Profile Benjamin Wandelt
Post:
Hi Sam -
the methods underlying cosmology@home and the computations have helped to train a machine learning algorithm that has bee used extensively in the day-to-day operations of the Planck mission. Have a look at my recent post on new directions for C@H in this forum for a quick update and news about a new focus for computations on c@h in the next months.

Best,
Ben
3) Forums : Cosmology and Astronomy : Calculated projetcs... (Message 22632)
Posted 8 days ago by Profile Benjamin Wandelt
Post:
Hi all -

My apologies for being non-responsive to your questions. In the current situation our mode of operation has changed and priorities shifted for a while. You really do not have to worry that we keep this project running only for the mountains of funding we receive for it - there are no mountains!

Have a look at my recent post in the Astronomy and Cosmology section of the forums where I have given an update and I am happy to report on a recent breakthrough in preparing a new kind of cosmological computation on cosmology@home.

Best regards,
Ben Wandelt
4) Forums : Cosmology and Astronomy : A new direction for Cosmology@Home (Message 22631)
Posted 8 days ago by Profile Benjamin Wandelt
Post:
Dear participants,

After the last set of updates a couple of years ago and with some hardware purchases the C@H site and the server are now running smoothly and stably. The high-precision outputs you are computing have been key in the day-to-day operations of extracting cosmological information from the Planck data. While we can still use these outputs for further analyses, the last Planck team publications have just appeared in the latest issue of Astronomy and Astrophysics, a professional journal for front-line, peer-reviewed research.

In fact, the updates I mentioned (led by Marius Millea) have made it possible to use the C@H platform for new kinds of cosmology projects. And we have plenty of ideas for new applications.

As a hint of what’s coming, have a look at this blog post that describes a new method we just published for simulating the non-linear formation of structures in the universe today. This is a much more challenging problem than what C@H is doing right now (which is to predict the properties of structure in the extremely early universe, where the much simpler linear theory works. In some ways the early universe is much easier to model than the universe today!). The main innovation in our paper is that we've found a way to split this very large computation into a very large number of much smaller pieces, making it possible for the first time to think about running such a non-linear simulation on C@H.

We are still working out the details but it looks like we will be able to set up C@H to run a very large---truly planet-scale---simulation of structure formation in the universe using all our participants’ computers distributed across the earth.

The main limitation we have at the moment is people to implement these ideas and actually make this happen. I am working on this and will keep you updated.

Thank you again for your continued support of cosmology@home.

Best regards,

Ben Wandelt
5) Forums : Cosmology and Astronomy : 'Serious gap' in cosmic expansion rate hints at new physics (Message 21679)
Posted 24 Apr 2018 by Profile Benjamin Wandelt
Post:
Hi -

This is directly related to what we are doing here - PICO, which we developed using your computations on C@H, is heavily used to derive the Planck/CMB constraints. The recent challenges have been used to validate the results, increasing our confidence in the Planck/CMB results.

As the referenced BBC article describes, there is a tension between the measurement of the expansion speed of nearby objects vs the expansion speed inferred when using the observed patterns in the ancient Cosmic Microwave Background, that reaches us from the furthest observable parts of the universe.
This could mean that the universe changed its expansion speed recently, which would woudl be an exciting discovery.
Unfortunately it is possible that the issue is just that one of the two data sets are wrong; and the results from the recent universe have historically not been as stable as the conclusions drawn from the distant universe. This is perhaps not what you expected, since the nearby universe ought to be easier to study... the problem is that it's more complex and therefore harder to interpret.

At this point we need additional data to arbitrate between the two possibilities of exciting new fundamental physics, and just one of the data sets being interpreted incorrectly.

Watch this space!
Best,
Ben
6) Forums : General Topics : Why do you participate in Cosmology@Home? Who is the \"most surprising\" participant? (Message 21470)
Posted 13 Jun 2017 by Profile Benjamin Wandelt
Post:
Great, thank you for your support.
I hope we won't disappoint!

All the best,
Ben
7) Forums : Cosmology and Astronomy : Dark Energy Demo Room (Message 21236)
Posted 15 Dec 2016 by Profile Benjamin Wandelt
Post:
Hi Jeffrey -

Remember to click inside the game before pressing S to start - it doesn't register the key stroke otherwise and nothing happens.

All the best,
Ben
8) Forums : Cosmology and Astronomy : Is the speed of light constant? (Message 21232)
Posted 13 Dec 2016 by Profile Benjamin Wandelt
Post:
Hi
Thanks for your post. Yes this is relevant to cosmology. At this point the best measurement of the claimed very precise prediction by the varying speed of light hypothesis is consistent with the world's best constraints coming from the Planck data analysis.
I am personally a bit sceptic regarding the claimed uniqueness of this prediction given that we know so little about the detailed physics at this epoch. If it is true the ever precise measurements coming from the Cosmic Microwave Background polarization and other probes will eventually be able to distinguish this model from other approaches that predict a range of possible values. If you're interested to know how this works (even if the data agrees with both models) ask me and I will tell you about relative model probabilities in Bayesian stats...

Till then,
All the best,
Ben
9) Forums : General Topics : Any status info? (Message 21138)
Posted 29 Jul 2016 by Profile Benjamin Wandelt
Post:
Hi Misho -

Thanks for your post!

For general background you could peruse the cosmic background pages on my home page at the University of Illinois. That material is still valid even if it has not been updated for a while.

Several more recent updates have been posted directly on the forum as well - check out the News section.

If you questions about the science, please do not hesitate to post in the Cosmology and Astronomy section of the forums, which we check periodically.

Best,
Ben
10) Forums : Wish list : Badges (Message 21066)
Posted 16 May 2016 by Profile Benjamin Wandelt
Post:
Hi again -

Any thoughts on any of the points in my previous post?
Comments?
Suggestions?

Cheers,
Ben
11) Forums : Wish list : Badges (Message 21063)
Posted 11 May 2016 by Profile Benjamin Wandelt
Post:
Hi all -

Very interesting idea. Just as a spontaneous thought - can we crowd source this?

As my contribution here is a list of ideas for badge names - loosely orderd from the nearby and more familiar to the more exotic or distant.

Moon
Planet
Star
Neutron Star
Black Hole
Star cluster
Dwarf galaxy
Galaxy
Galaxy Cluster
Filament
Wall
Void
Quasars
Baryons
Neutrinos
Dark Matter
Dark Energy
Gravitational Lensing
Cosmic Microwave Background Temperature
Cosmic Microwave Background Polarization
Big Bang
The Universe

Yes, I know I'm mixing a lot of things, from elementary particles to astronomical observables, but they are all important for cosmology (even the moon, for example some important constraints on gravity come from precision lunar ranging), so why not? There are of course many other things I could have put on, but I've limited the list to things/concepts that we know exist or must be there in some form or another. I also did not include theories etc... or names of famous cosmologists...

So if we took this as given, maybe some of the more graphically talented amongst you can have a go at submitting artwork (watch the format, there seems to be a conventional size for the badges etc... but I'm not the expert on that, so please ask the others writing in this thread.)

Cheers,
Ben

Edit: removed the second "Baryons"
12) Forums : Cosmology and Astronomy : How many black holes are there? (Message 20746)
Posted 23 Jan 2016 by Profile Benjamin Wandelt
Post:
Hi Peter -
This is a question that touches on current research themes... in other words we don't know the answer very precisely at this time. It's only been in the last year or two that cosmological simulations have had the ability to resove individual galaxies and include mechanisms for the formation of black holes (so-called sub-grid models, see below). Examples are the Horizon-AGN simulation run that was performed by my colleagues here at the Institut d'Astrophysique de Paris (one of the first such runs). Another is the EAGLE run done by a consortium of other groups. The links are worth checking out for impressive visualizations and movies of the simulation results.

The difficulty with these runs is that the detailed physics of black-hole formation works on much shorter time-scales and length scales than can be resolved in these large simulation volumes even with the largest current supercomputers.

For this reason the formation of black holes is not simulated from first principles but using prescriptions (called "sub-grid models") that compute the probability of black hole forming in a particular grid cell, and then randomly add a black hole based on this probability. The details of the black hole (ie the accretion disk physics etc) are also not simulated but the winds from the accretion disk etc are computed based on the density, temperature etc of the cell that contains the black hole).

As a result the number of black holes at any given time depend on the parameters of the sub-grid models. The approach is to run a few simulations with different plausible values of these parameters and then to compare the results with observations of the real universe.

So to answer your question: yes there are cosmological simulations that compute the fraction of total mass in gas, stars, black holes and even the abundances of various chemical elements etc. But the results do not just depend on fundamental laws of physics but on approximate "recipes" and particular choices of the parameters of these recipes. The results are difficult to validate since this is really frontier research.

For now comparison to deep astronomical observations are our best bet at validating the sub-grid models.

Hope this helps!

Best,
Ben
13) Forums : Cosmology and Astronomy : Dark Energy Demo Room (Message 20563)
Posted 6 Nov 2015 by Profile Benjamin Wandelt
Post:
Thanks Julie -
I hope you enjoyed the free mini-games. Let me know if you have any questions!
Cheers,
Ben
14) Forums : Wish list : OSX (Message 20291)
Posted 26 Aug 2015 by Profile Benjamin Wandelt
Post:
Hi, cosmology@home enthusiasts who are OSX users!

I'm happy to announce that the new cosmology at home server (currently in beta release here) supports OSX!

As you've noticed there's been a bout of recent activities and new developments, signs of more to come.

Let me take this opportunity to thank Marius, Kevin, and Mark who are driving these changes.

All the best,
Ben
15) Forums : General Topics : Appeal to Project Managers (Message 20249)
Posted 3 Jul 2015 by Profile Benjamin Wandelt
Post:
Hi -
Thank you for your message.

I agree that we have been lacking in our communication activities.

The good news is that we are taking active steps to improve the project at the moment. We have been using the small amount of funding we have on keeping C@H up. We had some downtime yesterday due to a hardware failure. This has now been resolved.

We are now working on a major upgrade of C@H this summer. This will involve
- migration of c@h to a new, more stable, and more robust server,
- upgrade to the latest BOINC version,
- some infrastructure changes that will allow us to push new code versions much more efficiently.

These changes will set us up for launching new cosmology applications (beyond the current CAMB).

More updates to follow.

Let me thank you for your patience and for your continued involvement in C@H.

Best regards,
Ben
16) Forums : Cosmology and Astronomy : Dark Energy Demo Room (Message 20237)
Posted 29 May 2015 by Profile Benjamin Wandelt
Post:
Hi all,

I am not sure I ever advertised this: a while ago I started putting together some interactive web apps to illustrate concepts related to the expansion of the Universe and dark energy. The first couple of interactive demos are up, so have a look!

One app is called "Expansion" and shows some surprising features of the cosmic expansion; in particular, how the universe can expand without a unique center!

The other is a simple game called "SuperNova Hunter" which illustrates some aspects of observing the universe to get a handle on the physical properties of dark energy. When you play it a few times you'll find yourself adopting a similar strategy to that used by actual astronomer who hunt supernovas (supernovae for those who had Latin at school) to learn about dark energy.

Have ideas for other expansion/dark energy concepts that could be illustrated with interactive apps? Post your responses here!

Thank you!

Best regards,
Ben

17) Forums : General Topics : Project News Updates (Message 13102)
Posted 25 Jun 2013 by Profile Benjamin Wandelt
Post:
Hi all

Many thanks for interest and your patience!

I just wanted to take a few minutes to thank you for your effort on behalf of cosmology@home. We have made great strides in the last years and I am very pleased to see that our servers held up in the recent Dutch Power Cow stampede!

An update from us on the progress we are making with cosmology@home is overdue. The first Planck analysis has been released and I am glad to report that Pico (the code that we are feeding and training with the results from cosmology@home) was used extensively during the cosmological parameter analysis. We have readied a major update for the website (including new hardware).

I just heard that the hardware has arrived and if there are no unforeseen problems it should come online later this week. Then we will deploy the website upgrades.

I will post more next week about the changes, also in other threads, but you've heard it here first.

Oh, and Go Dutch Power Cows!

And of course, thank you to all our other faithful supporters throughout the years!

All the best,
Ben
18) Forums : Cosmology and Astronomy : Featured Concept: Dark Matter (Message 11523)
Posted 31 Jul 2012 by Profile Benjamin Wandelt
Post:
Ok, so let me expand a bit on my comment in an earlier post "...a real chance of being resolved in the near future..." since it's now gone beyond just an insider rumor and there are a couple of more detailed science papers about it.

First in plain English: there is a real chance that a tell-tale signature of dark matter has now been observed.

Now in sciencese: a couple of analyses now see a line feature in the energy spectrum of gamma rays observed by FERMI satellite at an energy of around 129 GeV.

Why is this exciting? A line feature is exactly what would be expected if a massive particle annihilates and the release energy is liberated in gamma rays.

There are astrophysical sources of gamma rays as well, but they tend to be much more broad band, since the can produce gamma rays of a range of energies.

However, if two dark matter particles, each of mass 129 Gev moving at "normal" speeds (ie not close to the speed of light) run into each other then would decay at leastinto two other particles each carrying away 129 GeV of energy, and for symmetry reasons there would be no more and no less of that amount, leading to a well defined energy of the gamma rays. Counting up gamma rays detected by the Fermi satellite in bins of energy then leads to a big pile showing up in the 129 GeV bin - hence a line.

There are some who consider such a line signal a smoking gun of dark matter. And we may now have seen it.

One of the interesting properties of this line is that it is seen towards the galactic center (where there is a lot of dark matter but not away from the galaxy where we would not expect to see it if it were indeed dark matter. Also, the signal persists when the anaysis is re-done masking known astrophysical sources of gamma rays, just to exclude that some unknown mechanism, however unlikely, could produce such a line signal without dark particle decays being involved.

We had on of the authors of the first paper that found this line, Thorsten Brinkmann, at IAP a couple of months ago and we were all trying to pick apart his argument. In the end I thought it was pretty convincing.

Of course, it didn't take long for people to notice that this energy of 129 GeV was basically the same as the mass of the Higgs boson that was announced even more recently. Of course there are already model builders who are trying to explain this coïncidence.

Exciting times!

All the best,
Ben


19) Forums : Technical Support : Tasks will not complete (Message 11416)
Posted 14 Jul 2012 by Profile Benjamin Wandelt
Post:
Thank you - that makes sense. There weren't very many points where checkpointing was easy without a lot of additional coding. If you want to share your machine between different projects, it seems the best way to do that for now is to run cosmology@home exclusivelyfor a while and then switch over to the other projects.

But we'll keep this in mind for future versions of the kernel.

Best,
Ben
20) Forums : General Topics : Word Link at C@H (Message 11415)
Posted 14 Jul 2012 by Profile Benjamin Wandelt
Post:
Probability


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