Archive for 2017

Emergent gravity in galaxies and in the Solar System [GA]

Posted in The Universe and Stuff with tags , , on February 17, 2017 by telescoper

I’ve been meaning to do a blog post about Erik Verlinde’s  very interesting “Emergent Gravity” theory since it was first aired in November 2016, but never got round to it. However, this recent paper suggests that the new theory fails badly on scales of the Solar System. And when I say “badly”, I mean by seven orders of magnitude. That’s pretty bad.

Unless there’s something wrong with this analysis, this looks pretty terminal …

arxiver's avatararXiver

http://arxiv.org/abs/1702.04358

It was recently proposed that the effects usually attributed to particle dark matter on galaxy scales are due to the displacement of dark energy by baryonic matter, a paradigm known as emergent gravity. This formalism leads to predictions similar to Modified Newtonian Dynamics (MOND) in spherical symmetry, but not quite identical. In particular, it leads to a well defined transition between the Newtonian and the modified gravitational regimes, a transition depending on both the Newtonian acceleration and its first derivative with respect to radius. Under the hypothesis of the applicability of this transition to aspherical systems, we investigate whether it can reproduce observed galaxy rotation curves. We conclude that the formula leads to marginally acceptable fits with strikingly low best-fit distances, low stellar mass-to-light ratios, and a low Hubble constant. In particular, some unobserved wiggles are produced in rotation curves because of the dependence of the transition on the…

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Le Vin herbé

Posted in Opera with tags , , on February 17, 2017 by telescoper

Last night I went to the Wales Millennium Centre in Cardiff for the opening night of Welsh National Opera’s new production of Le Vin herbé  by Swiss-born composer Frank Martin. This isn’t a work with which I was previously familiar so I wasn’t sure what to expect, but then that’s why I usually particularly hard to get to see departures from the standard repertoire. It’s not that I’m at all bored with Mozart, Puccini et al but that it’s always good to keep an ear open for new things.  In fact there is only one performance of this piece in Cardiff this year before it goes on tour. Fortunately I was able to make it.

Le Vin herbé is based on the story of Tristan and Iseult ; the title refers to the potion that the two lead characters accidentally drink which makes them fall in love and thus betray King Mark of Cornwall, who is Tristan’s uncle and Iseult’s husband-to-be. Naturally tt all ends in disaster, with the two lovers both dying. But if the story makes you think of Wagner’s epic operatic telling of this legend, Tristan und Isolde then you need to think again, as this is a very different piece. Le Vin herbé is a much more intimate work, with a relatively small case and a band of just eight musicians (a piano and seven string players) who, in this production, were at centre stage throughout the performance rather than in the pit. The main characters are played by tenor Tom Randle (Tristan) and soprano Caitlin Hulcup (Iseult) – both of whom were brilliant – and some of their lines are also sung by the chorus and there are also solo storytellers to provide bits of the narrative. The set and staging is very minimal. In fact it’s more of a chamber oratorio than an Opera. Also the entire performances lasts under two hours, with no interval. Quite a lot shorter than Wagner’s version!

I think the instrumental music by Frank Martin is very fine indeed, and very well played by the musicians directed by James Southall, and the principals and chorus were in good voice. Having said that I think Martin’s writing for voices is less successful. The vocal lines consciously evokes mediaeval plainsong, which works quite well for the chorus but makes it difficult for the soloists to generate any melodic drive. It’s not helped by the libretto either, which is rather dry and undramatic. On the way home from the performance I couldn’t help wondering what it might have been like had the text been in mediaeval Latin! The staging was at times effective: some of the scenes between Tristan and Iseult were very moving, but the stage was too busy and confusing when the whole chorus got involved.

This probably sounds very critical, but I don’t mean it to be. There’s much to enjoy in this production, so I’d encourage you to go and form their own opinion. It’s on tour in Bristol, Milton Keynes, Llandudno, Plymouth and Southampton. Last night’s performance got a very warm reception from a pretty full house which, for an unusual work like this, is a very good sign.

A Blueprint for a Quantum Computer

Posted in The Universe and Stuff with tags , , , , on February 16, 2017 by telescoper

I’m a little bit late blogging about this topic, as it relates to a paper published on 1st February 2017, but it’s a pleasure to be able to draw your attention to an important paper by a group led by a former colleague of mine from the University of Sussex, Prof. Winfried Hensinger, known to his friends as “Winni”. In essence they have constructed a practical way to build a working quantum computer.

Here is the abstract of the latest paper which explains the significance of the work:

The availability of a universal quantum computer may have a fundamental impact on a vast number of research fields and on society as a whole. An increasingly large scientific and industrial community is working toward the realization of such a device. An arbitrarily large quantum computer may best be constructed using a modular approach. We present a blueprint for a trapped ion–based scalable quantum computer module, making it possible to create a scalable quantum computer architecture based on long-wavelength radiation quantum gates. The modules control all operations as stand-alone units, are constructed using silicon microfabrication techniques, and are within reach of current technology. To perform the required quantum computations, the modules make use of long-wavelength radiation–based quantum gate technology. To scale this microwave quantum computer architecture to a large size, we present a fully scalable design that makes use of ion transport between different modules, thereby allowing arbitrarily many modules to be connected to construct a large-scale device. A high error–threshold surface error correction code can be implemented in the proposed architecture to execute fault-tolerant operations. With appropriate adjustments, the proposed modules are also suitable for alternative trapped ion quantum computer architectures, such as schemes using photonic interconnects.

Here’s a short video explaining the setup

This result has generated a lot of good publicity for the group at Sussex, including a piece in the Financial Times and a personal appearance by Winni himself on Sky News.

It’s great to see the  Ion Quantum Technology group continuing to do really well and I’m sure the investments made in physics research at the University of Sussex over the last few years will bring even more exciting developments in the near future!

 

How Time Passes

Posted in Jazz with tags , , , on February 15, 2017 by telescoper

I don’t seem to have had much time recently to post any lengthy pieces about music, and today is no exception, but I couldn’t resist sharing this fascinating title track from the album How Time Passes which was recorded in New York City in October 1960. It features Don Ellis on trumpet and  Jaki Byard on piano (with Ellis doubling on piano sometimes to allow Byard to play saxophones) along with Ron Carter on bass and Charlie Persip on drums. The album is a fascinating collection of modern jazz performances informed by  contemporary classical music, a blend that came to be known as Third Stream. This track is particularly unusual because of its elastic approach to tempo – it is constantly speeding up and slowing down in a way that makes you wonder how the band stays together – but it also features some beautiful work on trumpet by Don Ellis.

 

P.S. As well as being a superb jazz musician, Don Ellis was also a fine composer. Among other things he wrote the theme music for the film The French Connection. Not a lot of people know that.

 

 

Cosmological Parameters from pre-Planck CMB Measurements: a 2017 Update [CEA]

Posted in The Universe and Stuff on February 15, 2017 by telescoper

Via arXiver, here’s a nice summary of the (strong) constraints on cosmological parameters that can be achieved from Cosmic Microwave Background experiments other than Planck. This is an important thing to do for a number of reasons, including that it might reveal interesting systematic differences between pre- and post-Planck data which merit further study.

The first author of this paper, Erminia Calabrese, will be joining us on the staff of the School of Physics & Astronomy at Cardiff University in May 2017!

arxiver's avatararXiver

http://arxiv.org/abs/1702.03272

We present cosmological constraints from the combination of the full mission 9-year WMAP release and small-scale temperature data from the pre-Planck ACT and SPT generation of instruments. This is an update of the analysis presented in Calabrese et al. 2013 and highlights the impact on $Lambda$CDM cosmology of a 0.06 eV massive neutrino – which was assumed in the Planck analysis but not in the ACT/SPT analyses – and a Planck-cleaned measurement of the optical depth to reionization. We show that cosmological constraints are now strong enough that small differences in assumptions about reionization and neutrino mass give systematic differences which are clearly detectable in the data. We recommend that these updated results be used when comparing cosmological constraints from WMAP, ACT and SPT with other surveys or with current and future full-mission Planck cosmology. Cosmological parameter chains are publicly available on the NASA’s LAMBDA data archive.

Read this…

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Mending Wall

Posted in Poetry with tags , , , on February 14, 2017 by telescoper

Something there is that doesn’t love a wall,
That sends the frozen-ground-swell under it,
And spills the upper boulders in the sun;
And makes gaps even two can pass abreast.
The work of hunters is another thing:
I have come after them and made repair
Where they have left not one stone on stone,
But they would have the rabbit out of hiding,
To please the yelping dogs. The gaps I mean,
No one has seen them made or heard them made,
But at spring mending-time we find them there.
I let my neighbor know beyond the hill;
And on a day we meet to walk the line
And set the wall between us once again.
We keep the wall between us as we go.
To each the boulders that have fallen to each.
And some are loaves and some so nearly balls
We have to use a spell to make them balance:
“Stay where you are until our backs are turned!”
We wear our fingers rough with handling them.
Oh, just another kind of outdoor game,
One on a side. It comes to little more:
He is all pine and I am apple-orchard.
My apple trees will never get across
And eat the cones under his pines, I tell him.
He only says, “Good fences make good neighbors.”
Spring is the mischief in me, and I wonder
If I could put a notion in his head:
“Why do they make good neighbors? Isn’t it
Where there are cows? But here there are no cows.
Before I built a wall I’d ask to know
What I was walling in or walling out,
And to whom I was like to give offence.
Something there is that doesn’t love a wall,
That wants it down!” I could say “Elves” to him,
But it’s not elves exactly, and I’d rather
He said it for himself. I see him there,
Bringing a stone grasped firmly by the top
In each hand, like an old-stone savage armed.
He moves in darkness as it seems to me,
Not of woods only and the shade of trees.
He will not go behind his father’s saying,
And he likes having thought of it so well
He says again, “Good fences make good neighbors.”

by Robert Frost (1874-1963)

 

Haydn and the Herschels

Posted in History, Music, The Universe and Stuff with tags , , , , , on February 14, 2017 by telescoper

Last night I was listening to a broadcast of a concert performance of Haydn’s “Creation” on BBC Radio 3, featuring the London Philharmonic under the direction of Sir Roger Norrington. During the interval (between Parts I and II) the presenter Sara Mohr-Pietsch cast doubt in the story (which I’ve heard quite often), that Joseph Haydn was at least partly inspired to write The Creation by a trip he took during a stay in England to see the observatory of astronomer William Herschel. This story is repeated in a number of places around the web, including here, from which source I quote:

On 15 June 1792. Joseph Haydn visited William Herschel – basoonist, composer, astronomer – at his observatory near Slough. Herschel introduced Haydn to the Milky Way and, quite possibly, the planet Uranus, which he’d discovered ten years earlier. Some say Haydn took this glimpse of the infinite as the inspiration for his oratorio The Creation. Seems plausible.

It does indeed seem plausible. It is a matter of record that Haydn did  visit the Observatory House in Slough on 15th June 1792, which is where William Herschel lived with his sister Caroline at the time. (Interestingly, the day before this visit Haydn was at Ascot watching the horse-racing.)

However, according to William Herschel’s own records he wasn’t at the Observatory House on this day. In fact he had been away since May 1792 visiting various locations in England and Wales, before eventually arriving in Glasgow to receive an honorary degree. The notion that Herschel provided Haydn with the inspiration to write The Creation is therefore false.

Or is it?

William Herschel may not have been at home when Haydn called on 15th June 1792, but Caroline certainly was: Haydn’s name is recorded in her visitor’s book on that date. In his diary Haydn makes a note of the dimensions of the telescope (40ft) but does not mention actually looking through it, which is not surprising if he was there during the day.  There’s no other record of this visit of which I’m aware that says for sure what happened on that day, but Caroline certainly could have described what she had observed during her career as an astronomer, both on her own and with William, and also shown Haydn drawings, catalogues and star charts. Caroline Herschel was an extremely accomplished astronomer in her own right, so who’s to say it was not she rather than her brother who provided Haydn with the inspiration for his oratorio?

So it could well be that it was Herschel that inspired The Creation after all, but Caroline rather than William…

Signs of the Data Innovation Institute

Posted in Biographical with tags on February 13, 2017 by telescoper

I’ve only been in my new office in the Data Innovation Research Institute for 5 months so it came as a big surprise to see that they’ve already started putting up the signs telling people where we are. In fact a couple of chaps came this  morning to do the necessary, and now we look very professional. It’s hard to tell that this used to be a chip shop.

dii_out

Please don’t tell the Health & Safety people about the power cable trailing through the window!

And here’s me answering the door to strangers…

dii_2

Thanks to Dan Read for taking that second one.

R.I.P. Nicolai Gedda (1925-2017)

Posted in Opera with tags , , , on February 13, 2017 by telescoper

I only heard yesterday the very sad news that the fine Swedish operatic tenor Nicolai Gedda passed away on 8th January 2017 at the age of 91.  The news wasn’t announced by his family until February 9th, which explains part of the reason I am so late to post a little tribute. This is from the first recording I ever heard of die Zauberflöte by Wolfgang Amadeus Mozart (made in 1964, conducted by Otto Klemperer) in which Gedda sings Tamino alongside the equally wonderful Gundula Janowitz as Pamina.  This CD played a huge role in getting me interested in Opera, so it is with special sadness but also special admiration that I say farewell to Nicolai Gedda.

R.I.P. Nicolai Gedda (1925-2017)

 

Cosmological perturbation effects on gravitational-wave luminosity distance estimates [CL]

Posted in The Universe and Stuff on February 13, 2017 by telescoper

Interesting paper about the effect of cosmological inhomogeneity on gravitational wave propagation. The effect could be import for the more distant sources likely to be detected with future experiments.

arxiver's avatararXiver

http://arxiv.org/abs/1702.01750

Waveforms of gravitational waves provide information about a variety of parameters for the binary system merging. However, standard calculations have been performed assuming a FLRW universe with no perturbations. In reality this assumption should be dropped: we show that the inclusion of cosmological perturbations translates into corrections to the estimate of astrophysical parameters derived for the merging binary systems. We compute corrections to the estimate of the luminosity distance due to velocity, volume, lensing and gravitational potential effects. Our results show that the amplitude of the corrections will be negligible for current instruments, mildly important for experiments like the planned DECIGO, and very important for future ones such as the Big Bang Observer.

Read this paper on arXiv…

D. Bertacca, A. Raccanelli, N. Bartolo, et. al.
Wed, 8 Feb 17
18/65

Comments: 16 pages, 3 figures

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