Archive for Cosmology

The Early Stages of Cosmic Inflation

Posted in The Universe and Stuff with tags , , , , on July 13, 2017 by telescoper

When asked to cite the article that first presented the theory of the inflationary Universe most cosmologists would probably offer the famous paper published by Alan Guth in 1981.

However, I recently stumbled across a paper by Demosthenes Kazanas that was published (in the Astrophysical Journal Letters in 1980. I hadn’t seen this paper before a few days ago, and I don’t think it is very well known. Here is part of the front page:

You can get the full paper here.

I know that there were other papers floating around in 1980 that got part of the way to the theory of inflation, but this one seems very close to the theory, e.g. talking about exponential expansion in the context of the cosmological horizon problem.

Interestingly, while Guth (1981) has garnered many thousands of citations, Kazanas (1980) has been cited fewer than 300 times.

Does anyone know the story of this paper, and why it has largely  been overlooked by the exponentially-expanding literature on cosmic inflation? And,while I’m on the topic, can anyone suggest other early contributions to the theory that have been similarly neglected? Please let me know through the comments box below.

 

 

 

Film Noir, Physics, and the Futility of Existence

Posted in Biographical, Literature, The Universe and Stuff with tags , , , , , on July 5, 2017 by telescoper

Last night I decided to treat myself to the umpteenth viewing of a DVD of the  classical film  Double Indemnity. It’s a great movie that repays repeated viewing and is historically important for many reasons, not least because when it was released in 1944 it immediately established much of the language and iconography of the genre that has come to be known as Film Noir , which I’ve written about on a number of occasions on this blog; see here, for example.

After watching the film I had a look on Twitter to see if I had any messages and saw a thread about how modern physics inspires, in some people, an all-pervading sense of existential angst.  In the light of that discussion I decided to use my morning off to rehash that old post and add a few embellishments.

It’s difficult to define exactly what turns a film noir, but there are some common characteristics. First the male lead protagonist is far from the dashing romantic character portrayed in mainstream Hollywood fare. Often a troubled and dysfunctional character, cynical and hard-bitten, distrustful and alienated, the classic noir anti-hero is often a private investigator or in any case a loner who lives in a kind of moral vacuum. To counterpoint this, the female lead is usually a femme fatale, glamorous but duplicitous, sexy and dangerous, manipulative and assertive. There are definitely shades of Macbeth in that the female lead is usually a more compelling and impressive personality than the supposed hero. The inversion of stereotypical roles also serves to hold a “dark mirror” up to society, an effect which other elements of these films also strive to achieve.

The plots usually deal with the seedy side of human life: crime, betrayal, jealousy and revenge, much of it sexually motivated. Narrative strategies involve repeated use of flashbacks, first-person voiceovers, dream-like sequences, and unresolved episodes that emphasize the overall lack of moral direction. The photography is dominated by high contrast lights surrounding the protagonists with dark, threatening shadows while odd angles and unbalanced framing produce unstable, disorienting images. The chiaroscuro lighting makes even mundane encounters seem charged with danger or erotic suspense.

di6

This is a still from Double Indemnity which shows a number of trademark features. The shadows cast by Venetian blinds on the wall, the cigarette being smoked by Barbara Stanwyck and the curious construction of the mise en scene are all very characteristic of the style. What is even more wonderful about this particular shot however is the way the shadow of Fred McMurray’s character enters the scene before he does. The Barbara Stanwyck character is just about to shoot him with a pearl-handled revolver; this image seems to be hinting that he is already on his way to the underworld even before he arrives in the room.

Noir settings are almost exclusively urban: the resulting iconography consists of images of dark night-time cities with rain-soaked streets reflecting dazzling neon lights that intrude into the picture and fracture the composition. Interiors are almost always cramped and claustrophobic: dingy hotel rooms, night clubs or even the backs of taxi cabs. The dark outside world presses in on the characters and is full of danger. Soundtracks often include jazz in the bebop style from the late 1940s or early 1950s, with its jagged melodic lines and stuttering rythms, emphasizing the psychological instability displayed by the characters and settings.

The protagonists are trapped, perhaps just by mischance, in an alienating lonely world, usually a night-time city, where they are constantly in danger for their lives. The chaotic, random violence of this world gives rise to feelings of persecution and paranoia and a sense that life is absurd, meaningless, without order or purpose, and governed by contingency rather than design.

Much has been written about the origins of Film Noir, but it does seem clear to me that, although it is essentially an American style, it owes many of its roots to European existentialism, a point further reinforced by the fact that many great movie directors of the noir period (including the great Billy Wilder, who directed Double Indemnity) were in fact European emigres.

Anyway, I digress. What I wanted to say really was that during the course of watching all these wonderful films from a bygone age it struck me how much the language and iconography of modern cosmology shares this existentialist heritage. Our new standard cosmological model is full of references to the “dark” sector (dark matter and dark energy) which dominates the energy budget of the Universe, but which not just invisible but also unfathomable. The cosmos is lit by garish starlight from small islands of luminosity embedded in this sea of darkness. Long chains of bright galaxies stretch across space like rows of streetlights whose glare fractures and disturbs the celestial dark. We cling to a precarious existence on a tiny rock that is surrounded by danger. Even the stuff from which our atoms are made is completely overshadowed by alien matter. The universe is oblivious to us and we are irrelevant to it.

But it’s not only the surface imagery of cosmology that resembles that of a noir movie. The existentialist trend runs deep. Cosmology seems to be abandoning the idea that there is a design behind it all. The idea that there is a single explanatory principle “a theory of everything” that accounts for why our Universe is the way it is and why life is possible within it, is losing ground to the idea that there is a multiverse in which all possible laws of nature are realised; we just live in a place where life happens to be possible. I’m not at all convinced that it is a good route for science to follow, but many cosmologists seem to be accepting this kind of thing as the best we will ever do to explain the Universe.

The physicist Steven Weinberg summed up the way this view of the Universe challenges us:

It is almost irresistible for humans to believe that we have some special relation to the universe, that human life is not just a more-or-less farcical outcome of a chain of accidents reaching back to the first three minutes, but that we were somehow built in from the beginning. … It is very hard to realise that this is all just a tiny part of an overwhelmingly hostile universe. It is even harder to realise that this present universe has evolved from an unspeakably unfamiliar early condition, and faces a future extinction of endless cold or intolerable heat. The more the universe seems comprehensible, the more it also seems pointless.

In an interview he put it thus:

I believe that there is no point in the universe that can be discovered by the methods of science. I believe that what we have found so far, an impersonal universe in which it is not particularly directed toward human beings is what we are going to continue to find. And that when we find the ultimate laws of nature they will have a chilling, cold impersonal quality about them.

The influential American horror writer Howard Phillips Lovecraft (known to his friends as “H.P.”), wrote a letter in 1919 that argued much the same:

As you are aware, I have never been able to soothe myself with the sugary delusions of religion; for these things stand convicted of the utmost absurdity in light of modern scientific knowledge. With Nietzsche, I have been forced to confess that mankind as a whole has no goal or purpose whatsoever, but is a mere superfluous speck in the unfathomable vortices of infinity and eternity. Accordingly, I have hardly been able to experience anything which one could call real happiness; or to take as vital an interest in human affairs as can one who still retains the hallucination of a “great purpose” in the general plan of terrestrial life. … However, I have never permitted these circumstances to react upon my daily life; for it is obvious that although I have “nothing to live for”, I certainly have just as much as any other of the insignificant bacteria called human beings. I have thus been content to observe the phenomena about me with something like objective interest, and to feel a certain tranquillity which comes from perfect acceptance of my place as an inconsequential atom. In ceasing to care about most things, I have likewise ceased to suffer in many ways. There is a real restfulness in the scientific conviction that nothing matters very much; that the only legitimate aim of humanity is to minimise acute suffering for the majority, and to derive whatever satisfaction is derivable from the exercise of the mind in the pursuit of truth (from Letter to Reinhardt Kleiner  (14 September 1919), in Selected Letters I, 1911-1924 edited by August Derleth and Donald Wandrei, pp. 86-87).

I’ve thought about this quite a lot over the last few years and am gradually finding myself more and more in agreement with Lovecraft. I would say further that that one of the few things that make life bearable is the futility of existence. Futility is very reassuring. If all the shit that happens in this world were designed to serve some higher purpose then that really would be terrifying. And even more reassuring than its futility is the knowledge that we will soon return to dust and be quickly forgotten.

Here’s  Weinberg again, from the same interview quoted above:

…if there is no point in the universe that we discover by the methods of science, there is a point that we can give the universe by the way we live, by loving each other, by discovering things about nature, by creating works of art. And that — in a way, although we are not the stars in a cosmic drama, if the only drama we’re starring in is one that we are making up as we go along, it is not entirely ignoble that faced with this unloving, impersonal universe we make a little island of warmth and love and science and art for ourselves. That’s not an entirely despicable role for us to play.

Inspired by this, I’m going to make a point of existence not by doing science nor creating a work of art, but by making a nice cup of tea.

Cosmology Caption Competition

Posted in Biographical, The Universe and Stuff with tags , , on July 3, 2017 by telescoper

I’ve been a bit busy today so in lieu of a proper post I thought I’d try for a bit of audience participation. In one of the discussion sessions at last week’s workshop on Isotropic Random Fields in Astrophysics I was called upon to deliver a very short impromptu talk on cosmological applications of Burger’s Burgers Equation, during the course of which the following photograph was taken. Appropriate (or inappropriate) suggestions for captions, please, through the comments box!

Cosmological Wave Mechanics

Posted in The Universe and Stuff with tags , , , , on June 15, 2017 by telescoper

As promised here are the slides I used for my talk yesterday at Imperial College. I stole some of them from an old presentation given by Chris Short, who was a PhD student of mine when I was at Nottingham. Chris now works for the Met Office, working on rather different application of fluid mechanics!

Cosmology at a Crossroads – Poll

Posted in The Universe and Stuff with tags , , , on June 13, 2017 by telescoper

A short comment piece by Wendy Freedman has appeared in Nature Astronomy; there’s a free version on the arXiv here. It gives a nice perspective on the current debate about the value of the Hubble constant from the point of view of an expert on cosmological distance scale measurements.

The abstract is here:

We are at an interesting juncture in cosmology. With new methods and technology, the accuracy in measurement of the Hubble constant has vastly improved, but a recent tension has arisen that is either signaling new physics or as-yet unrecognized uncertainties.

For the record, I’d go for `as-yet unrecognized uncertainties’, primarily because this field has a long history of drastically underestimated error-bars!

However, the publication of this piece gives me the excuse to resurrect the following poll, in which I invite you to participate:

Wave Mechanics and Large-scale Structure

Posted in Books, Talks and Reviews, The Universe and Stuff with tags , , , on May 24, 2017 by telescoper

I thought I’d share the slides I used for the short talk I gave last Thursday at the Osservatorio Astronomico di Bologna, on the topic of Wave Mechanics and Large-scale Structure. I’ve posted about the general idea underpinning this workhere, and here are some links to references with more details of the cosmological setting, including a couple of papers by myself and Chris Short on some of whose old slides I based the talk.

http://adsabs.harvard.edu/abs/1993ApJ…416L..71W
http://adsabs.harvard.edu/abs/1997PhRvD..55.5997W
http://adsabs.harvard.edu/abs/2002MNRAS.330..421C
http://adsabs.harvard.edu/abs/2003MNRAS.342..176C
http://adsabs.harvard.edu/abs/2006JCAP…12..012S
http://adsabs.harvard.edu/abs/2006JCAP…12..016S
http://adsabs.harvard.edu/abs/2010MNRAS.402.2491J

I had a few problems with the movies during the actual talk, and they probably don’t work in this embedded version. There are a few formatting errors in the slideshare version too, but hopefully you can figure out what’s going on!

Gravity in the Quantum Vacuum

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

Yeterday I noticed an interesting paper which has been on the arXiv for a few months but which has just been published in Physical Review D and has been highlighted by the Editors of that esteemed journal. The authors are Qingdi Wang, Zhen Zhu and Bill Unruh – all of them from the University of British Columbia in Vancouver.

Here is the abstract:

You can click on the image if it is too small to read. As you will see it suggests that we may have been thinking about the effect of vacuum energy in completely the wrong way in the context of Dark Energy.

It’s a long paper (35 pages) which I haven’t had time to work through completely yet, and I don’t know whether it will stand up. I have to say, though, that I’ve long left that the problem of dark energy will only be solved by a fundamental reappraisal of the underlying physics, rather than adding new fields or other such contrivances.

I’d be interested in comments from people who have read the paper thoroughly. I’m flying back to Blighty this evening so I hope I can study the article more thoroughly on the plane.