Watch This Space II

Mike Hewson
Mike Hewson
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Topic 198300

I've managed to get some time off work for being a good lad for a sufficient number of contiguous weeks. Now is there perchance a local scientific conference being held in honor of my annual leave ? No, not actually ....... :-))

Seriously I have registered for the 8th Australasian Conference on General Relativity and Gravitation at Monash University 2nd - 4th December. A mere two stone's throws away from where I live, so I thought why not ? This is being held by the Australasian Society for General Relativity and Gravitation. I will be attending the banquet for same on the evening of the 1st : ten years of me being at E@H FWIW. See, the planets are aligned ...

Now a glance at the plenary speaker list :

Nicole Bell (Melb)
Tamara Davis (QLD)
Joerg Frauendiener (Otago)
David McClelland (ANU)
Michael Tobar (UWA)
Bob Wald (Chicago)
Alex Vilenkin (Tufts) (to be confirmed)

... all seriously clever people. I probably should have at least a glance at the publications of these people before I attend. Special notes : Mr McClelland is a key player in the 'squeezed light' aspect of the LIGO detectors, and Dr Bell is from the same physics department that I was taught at 1978-80.

In any event I will sit up the back and keep quiet. Take notes. See if I can pick up the lingo, as it were, that the professionals use when they present stuff to each other. Goggle at the pictures etc.

I will report back.

Cheers, Mike.

( edit ) Next task : find out what a 'plenary' is. Maybe I'll have to get one made and bring it along. Something like that. :-)

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
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Watch This Space II

Mr Vilenkin has been firmed up to a yes and he seems to be a really interesting guy ( see Many Worlds in One: The Search for Other Universes and The Principle of Mediocrity ).

Quote:
Due to popular demand, the deadline for submission of abstracts has been shifted to Friday 13 November.


though I'm not sure quite what that implies operationally in the scheme of such things. Anyone ?

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
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There is an interim

There is an interim presentation list which shows much of interest. Many are from my alma mater of Melbourne Uni plus the host Monash University. Of special note is that Monash has a tremendous long standing reputation in the IT area particularly. I fondly remember an open day there in ~ 1977 where I got to play a text based Star Trek game - type commands in and the output via dot matrix printer. I was enthralled.There will be several about the topic dear to our hearts here at E@H : continuous gravitational wave searches from LIGO/Virgo data. :-)

Cheers, FNQ Correspondent

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Gary Roberts
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I was intrigued by this

I was intrigued by this particular abstract - particularly the last sentence and particularly due to my complete ignorance about the concept of wormholes. Make sure you get all the goss on that particular tidbit. You can then explain it all to us 'lesser mortals' :-).

Quote:

Black holes from domain walls and vacuum bubbles

Alex Vilenkin
Tufts University

Many particle physics models predict the existence of a number of vacuum states with different energy densities. Bubbles of different vacua could then be formed during inflation in the early universe. A positive energy bubble will expand with acceleration, as long as its energy density is lower than that in the inflating background. But when inflation ends, the bubble will decelerate and will eventually form a black hole. The resulting population of black holes can have significant astrophysical effects, and for some parameter values could even provide seeds for the observed supermassive black holes. Each black hole produced in this way will have an inflating universe inside, connected by a wormhole to the space outside.

Cheers,
Gary.

Mike Hewson
Mike Hewson
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Ooooh, I'll be there for the

Ooooh, I'll be there for the goss & tidbits particularly Gary. :-)

The program shows that I will be able to hear all the topics listed. So I must practice up my drinking-from-a-firehose skills. :-)

Also I note that Karl Wette from AEI at Hanover will be presenting, so I intend to kidnap him ( just overnite though ) and grill him mercilessly under hot lights. Please don't let him find out about this Cunning Plan. :-)

{ Also I have been preparing for a while one of my tutorial type threads to give an insight - as I currently understand - on what Special & General Relativity are and crucially how they relate ( pardon the pun ). I have researched much of the mathematics which I aim to disclose in the original intended Einstein mindset ie. why was his gravitational theory so brilliant ? Think geometry but in four dimensions, and with an interesting type of 'distance measure'. My usual be-kind-to-the-layman effort. }

Cheers, The FNQ Correspondent

BTW : yes, the monsoon is developing beautifully. I awoke at 4am on account of the sounds of a small dog being slaughtered. That turned out to be the magnificent calls of a gaggle of conversing tropical birds in a downpour. Spell binding.

( edit ) Alex Valenkin is a noted theorist on the subject of "eternal inflation" where universes beget universes. So ours is the spawn of another and its turn is spawning others. This is quite credible actually on theoretical grounds and his proposal here is that black holes hide that spawning behavior from us. While the question of whether one could demonstrate that by observation in this universe is moot, it is the type of imaginative thinking I adore.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Jim1348
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RE: Alex Valenkin is a

Quote:
Alex Valenkin is a noted theorist on the subject of "eternal inflation" where universes beget universes. So ours is the spawn of another and its turn is spawning others. This is quite credible actually on theoretical grounds and his proposal here is that black holes hide that spawning behavior from us. While the question of whether one could demonstrate that by observation in this universe is moot, it is the type of imaginative thinking I adore.


Then please ask him if dark matter can be sensed only gravitationally but not by direct observation, how feasible is it that it exists in another dimension (i.e., a parallel universe).

At least you can imagine it, so that is a start.

tullio
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The XENONIT experiment

The XENONIT experiment looking for dark matter has just started at Gran Sasso National Laboratory in Italy. It uses 3500 kg of liquid xenon cooled at -95 C. It is managed by INFN (Istituto Nazionale di Fisica Nucleare) and its scientific director is Elena Aprile of Columbia University.
Tullio

Mike Hewson
Mike Hewson
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Lunchtime Report Day 1 : -

Lunchtime Report Day 1 :

- yep it's a firehose alright ! Plus a bit of osmosis if you trim the vast amount going past.

- The very enthusiastic talk by Tamara Davis was great. She presented the state of the art of the overall view of the cosmos and what drives it.

- Interestingly even without accounting for ( distant ) supernova data ( Saul Permutter's Nobel for demonstrating acceleration of expansion over and above the Hubble flow imparted via the Big Bang ) there is ample evidence for a dark energy - and dark matter - coming out of the Planck mission data.

- In short one can't get a good fit for what are called the higher order multipole moments ( fine structure narrow angle aspects of the CMB pattern ) without putting in the so-called lamda and CDM parameters into the models. The values, now orthogonally gained mind you, agree to good tolerance with the SN et al data anyway.

- so dark energy/matter are here to stay. This is phenomenological mind you ie. some stuff with such influences must exist. This is now well advanced from say a decade ago where one had a 'concordance' viewpoint ( which cosmologist agrees with whom ). Now one has to agree with Planck findings, as a science ought.

- that still leaves burning questions as to the identity of The Dark Duo. In that regard the field is well open. A naive attempt to construct dark energy from the vacuum leaves one wanting for some 100 orders of magnitude. Epic fail. It seems that hope is being lost there in the form of some supersymmetry ( SUSY ) rescue/offset ie. a whole new class of quite undiscovered fundamental particles that persist in not showing up. In any case SUSY still requires an unheard of near cancellation from those 100 orders down to a magnitude that produces a piddling 10^[-40] repulsion in your living room.

- still at least the problem has better definition now and so, as always, the theorists must move on to come up with a better method. FWIW IMHO I'd take heed of what Dirac said about renormalisation ( modelling with deliberate intent to ignore exceeding small scale features of spacetime ) : it's mathematically unhealthy and probably a wrong turn.

- of course a proper meld of GR ( or a small scale congener of ) with QM is the key procedure here. Volunteers ? :-)

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
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Baryon Acoustic

Baryon Acoustic Oscillations

Baryons are the 'heavy' matter particles essentially protons and neutrons of the everyday world. After the Big Bang but before the surface of last scattering was formed ( some ~400K years later ) that gave us the CMB now, there was a interval where the evolution of the universe was dominated by radiation pressure from hot photons. Now one can take the Planck data and run time backwards, or alternately run forward from the BB to yield probable distributions of matter, including dark matter.

Basically the pattern of matter distribution, dark plus visible, evolves a certain way with photon interaction and then a different way once photons can no longer ionise the ( mainly hydrogen ) atoms. The extremely high density of the universe meant that the speed of sound early on was of order ~ 1/2 speed of light. Sound ? Yes sound. One particle bumps into the next, which hits its neighbor and so on and so forth. A chain of fast collisions in a directed and coherent manner to transfer kinetic energy. So waves of density run back and forth across the universe at it was back then.

So that is where the phrase 'acoustic oscillation' comes from ! :-)

Once the matter is decoupled from ( most ) photons then the matter ( again dark and visible ) start to clump together and their 3D distributions tend to follow one another. Dense areas become more dense and sparse areas more sparse. But there exist important disparities b/w the two though ( dark vs visible ). Contrast this with dark energy which is ( currently understood to be ) a constant, or nearly so, across all of spacetime.

If you like one can think of matter as in two parts : Self Evident & Obscure. Seems less mystical. Alex Valenkin's talk hypothecates that black holes of a large range of sizes form fairly readily if one assumes quantum mechanical ( tunneling actually ) effects that modulate the classical action of general relativity. Plugging in some real numbers into the model yields (a) consistency, (b) within 'reasonable' range and (c) testable by observation. On the face of it at least, such black holes may be of sufficient total quantity to make up a large fraction of the dark matter fraction that seeks explanation.

Now Gary back to your wormhole query : as a byproduct of the above model one generates black holes of a particular type of pedigree. Such BH's have the usual event horizon to external observers once formed. However the posited mechanism of formation ( an all too complex story of condensing spacetime domains, that I got totally lost within ) yields the formation of 'two sides to the same coin'. So one gets a single black hole seen from two distinct spacetimes, which in a geometric sense is described by the lower dimensional analogy of 'wormhole'.

Interestingly another prediction of this construct is the possible quantum correlation of entangled particle pairs, one of which stays in our universe with its 'twin' escaping through to the 'other' universe. The time window of this opportunity for this to happen is relatively brief, just leading up to the closure of the light world lines. Whether that leads to a testable observable prediction seems moot at present.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
Mike Hewson
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Now here's a thing I

Now here's a thing I overlooked. We know that neutrinos have non-zero rest mass ( this year's Nobel ). Strictly speaking what experiment discloses is the so-called 'mass squared difference' b/w the underlying three neutrino types ( complex ). Only at most one of them can be of zero mass, but maybe none of them are. Cosmic BAO studies have placed bounds on their masses which are of the order of milli-electron volts. About. :-)

Cheers, Mike.

( edit ) don't panic if all/any of what I report upon sounds odd. It all is severely anti-intuitive.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Mike Hewson
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Karl Wette gave an excellent

Karl Wette gave an excellent talk, in the sense that I understood it from go to whoa. So nice reality check for me there ! And he escaped kidnapping .... :-)

He outlined the parameter space that our E@H work units trawl through looking for significance, with especial emphasis on how one designs the 'metric' or stepping method of proceeding through said parameter space. The base idea is to have some confidence consistent across the search without to much variation. Note that we have around a half dozen parameters that are manipulated by our work unit generator. Karl frequently works with Reinhard Prix on such matters.

About one quarter of the shorter 20 minute presentations I literally could not follow anything b/w "Hello, my name is " and "Thank you for listening. Any questions ?". :-)

The talk of Andrew Melatos was of persistent GW's from glitchy milli-second pulsars ( MSP's ). These objects are a target of interest to E@H as a potential source of continuous signals. Now a glitch is a transient spin-up in the pulsar's rotation rate, the onset is likely no more than ~ a minute's duration say, and there follows a 'relaxation' back to the prior rate of ( negative ) frequency derivative. The mechanism he postulated was very QM : spin vortices deeper within the neutron star where the behaviour is labelled as 'superfluid' ( don't ask ).

Think of these as little whirlpools within, so they spin around and thus carry angular momentum. A glitch is caused by shifts of these internal vortices toward the outer crust of the star. Thus much like the rotating ice skater then moving one's arms outwards slows the rotation rate in order to conserve angular momentum.

However this gives a non-axisymmetric rotating mass distribution and thus will/ought generate gravitational waves. For a while at least until such power is bled away. This reverts the discussion into what are the various modes that pulsars lose energy during their spindown. Recall that honest researchers will admit to firmly knowing not a lot in truth of how even the electromagnetic emission of pulsars is generated in detail.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

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