A&C Reference Library - Astronomy & Cosmology Resources

[ranyart]

Originally posted by marcus
It was Ranyart who mentioned this one

http://arxiv.org/hep-th/0311030

"Black Holes in de Sitter Space: Masses, Energies and Entropy Bounds"

a paper by Corichi and Gomberoff analysing a black hole (entropy, hawking radiation, evaporation and all that) in the "isolated horizon" situation.

In that situation there are two horizons---the BH's own event horizon and a cosmological horizon (from beyond which nothing can ever come)
Ashtekar has been doing a lot of research on this situation. It is realistic in the sense that assuming a positive cosmological constant we really do have a cosm. horizon. Accelerating expansion causes it.

Having the other horizon helps limit things and makes it possible to do analysis where one could not before (with the BH just sitting by itself in an infinite expanse of space).

A couple of other BH articles came to light recently
-------------------

Maulik Parikh
http://arxiv.org/hep-th/0402166
"Energy Conservation and Hawking Radiation"
---------------------

Maulik Parikh and Frank Wilczek
http://arxiv.org/hep-th/9907001
"Hawking Radiation as Tunneling"

This paper may allready be on PF somewhere, but this is a recent update:http://uk.arxiv.org/PS_cache/gr-qc/pdf/0402/0402009.pdf

Its quite an interesting read, gives detailed and clear perspective outlines, and the citation/referal pages are a who's who of current Quantum Gravity community

 

[marcus]

Roser Pello and the most distant object

Meteor pointed us to the mid-pyrenees observatory
finding a z = 10 galaxy
(and GedankenDonuts gave a link too) then Nereid came up with
the scientific article co-authored by Roser Pello

http://www.edpsciences.org/papers/aa/pdf/press-releases/aaga201.pdf

here is a picture of Roser, she looks pleased to have found the galaxy
http://webast.ast.obs-mip.fr/people/roser/

z=10 means that the universe has expanded 11-fold since
the light issued from that galaxy


so while the light was traveling to get to us, distances between things became eleven times larger.
that means it was a long time that the light was traveling, estimated 13.2 billion years

for a calculator to calculate stuff like that try
Siobahn Morgan's online cosmology calculator

http://www.earth.uni.edu/~morgan/ajjar/Cosmology/cosmos.html

homepage for Siobahn also with photo
http://www.earth.uni.edu/smm.html

putting in the usual 71 for H, 0.73 for Lambda and 0.27 for matter density, we get that the object Roser and the others found is currently 31.5 billion light years from us and receding at a speed of 2.3 times the speed of light

 

[marcus]

Evaporating planet of 0.7 Jupiter mass

http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=34567
link courtesy Nereid, see her thread on this
"Osiris, a chthonian planet"
https://www.physicsforums.com/showthread.php?s=&threadid=13989

 

[Janus]

Ephemeris Generator

Here's a nice Ephemeris Generator:

http://ssd.jpl.nasa.gov/cgi-bin/eph

 

[wolram]

http://map.gsfc.nasa.gov/

some major and minor observatories, loads of links and info.

 

[wolram]

http://www.school-for-champions.com/science/gravity2.htm

gravity equations lots of basic stuff.

 

[wolram]

http://www.go.ednet.ns.ca/~larry/stars/starform.html

how stars are formed.

 

[marcus]

wolram thanks for adding these links to the reference thread!
the interactive tutorial on gravity is a good idea
(with the mild online quizes to self-check understanding)
the history of formation of a star like the sun was
informative (at least for me) by telling central and surface temperatures at each stage and time in that stage and
plotting the protostar's approach to the main sequence on the HR diagram---gives a more detailed story helping imagine how the
sun came into being

 

[wolram]

http://calspace.ucsd.edu/virtualmuseum/Glossary_Astro/gloss_a-f.shtml

GLOSSARY of terms.

 

[marcus]

http://relativity.livingreviews.org/Articles/lrr-2001-4/

Clifford Will
Confrontation between General Relativity and Experiment
----------

http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html

Tom Roberts
Experimental Basis of Special Relativity
(from the Physics FAQ)
-----------

these are two links that Russ says Nereid supplies in her posts
responding to folks challenging GR and SR

 

[meteor]

This paper seems interesting:
"Distance measures in cosmology"
David W. Hogg
http://arxiv.org/abs/astro-ph/?9905116

It must be good given that I really enjoyed the pdf course of special relativity of D. Hogg

 

[marcus]

A recent set of lectures
http://www.mpia-hd.mpg.de/homes/rix/Lecture.html

Rix is director of the MPI for Astronomy
the lectures are winter 2003-2004
by Matthias Bartelmann


a recent article by Alan Guth
"Inflation"
http://arxiv.org./astro-ph/0404546

a new pedagogical paper on the standard view of
the early universe
seems clearly written, 44 pages
by David Langlois
http://arxiv.org./hep-th/0405053

 

[marcus]

the Friedmann equations (the basic equations of cosmology)
just to have them handy for reference:


in units where c = 1:

\frac{a''}{a} = - \frac{4\pi G}{3}(rho + 3p)

(\frac{a'}{a})^2 = \frac{8\pi G}{3}rho - \frac{k}{a^2}


on first encounter with F. eqn. people often get confused by
the fact that Greek letter rho (for density) looks like Roman p (for pressure)
so I spell rho out here instead of using the symbol. The rho and p here are inclusive of all forms of energy from ordinary matter to dark energy.

k is a spatial curvature term, often set to equal zero since the universe is seen to be spatially flat either exactly or to a good approximation

a is the spatial scale factor in the standard cosmology metric (socalled FRW metric) and a increasing means distances between points are getting larger IOW space is expanding. The prime is its time derivative, so a' is rate of increase of a and a'' is a measure of acceleration.

----------very sketchy discussion--------
in cosmology almost nothing has pressure besides the dark energy
and for dark energy the most commonly assumed equation of state is
p_X = - rho_X
(thats what you get from a vacuum energy or a constant energy density associated with the cosmological constant, the typical dark energy idea)

IIRC the estimated average density for our universe at the present is
about 0.83 joules per cubic km
this includes the estimates of everything: visible matter, unseen matter, dark energy, light energy, neutrinos etc.
this energy density accords with the observed expansion rate and the observed flatness.


Dividing a'' by a makes the arbitrary length unit go away and you get a measure of acceleration that is just a reciprocal time squared.

Dividing a' by a gets rid of the length unit and after squaring you have
a reciprocal time squared there too. So in both equations the LHS is a reciprocal time squared.

rho and p have the same units (the unit of energy density is the same as that of pressure, in any coherenent system of units)
and multiplying by G will give, on the RHS as well, a reciprocal time squared

the point about dark energy is that as an energy density it contributes to the slowing of expansion by contributing to rho
just like any other type of energy including matter
so by contributing to rho, dark energy favors contraction

but dark energy is 3 times more influential as a pressure and in that way (by the negative pressure) it makes the whole RHS of the eqn positive and favors accelerating expansion

 

[sol2]

Here we provide you with an exercise to explore the possible universes governed by the Friedmann equation (equation (11.19) in the text). We use a simple applet to integrate the Friedmann equation for a range of models. (Note that this requires Java running on your browser.) On the applet below you can enter a value of Omega (density of the universe), a value of Lambda (the cosmological constant), and select a curvature (positive, zero, or negative). Note: This exercise provides a qualitative feel for the relative behavior of the Friedmann equation with respect to cosmological parameters. It does not provide detail models for comparison with observed cosmological values of omega or Hubble time



http://astsun.astro.virginia.edu/~jh8h/Foundations/Friedmann.html

 

[marcus]

sounds like fun, sol
here is a source on neutron stars
including detailed accounts of the stages of
Type II supernova collapse and the layer structure
of a neutron star
http://arxiv.org./astro-ph/0405262

 

[sol2]

Thank you Marcus,

I have been developing well with this kind of information. I hope others will benefit too.

http://online.itp.ucsb.edu/online/plecture/thorne/oh/08.gif

Some will appreciate the understanding there, of all the maths. Klein's ordering of Geometires as they have been shown through Patricias link of what is required of String theory in terms of those maths would have been laying one over the other, but in the Bose Nova, a culmination?

With Omega, critical density must still play a part in our understanding of this dynamical world in the classical realities? But when it comes to QM, how shall we understand the issues presented in cosmology, might also speak to QM as well?

Do you "follow" Brane world collisions?

 

[marcus]

I have not downloaded this----it is a long review paper on the physics of GRB: 159 pages. It probably could be mined for answers to questions about what causes GammaRay Bursts and what GRB events are actually like. the paper has been accepted by "Reviews of Modern Physics" so I would expect it to be suitably mainstream and authoritative.


http://arxiv.org/astro-ph/0405503
The Physics of Gamma-Ray Bursts
Tsvi Piran
159 pages, 33 figures, accepted for publication in Reviews of Modern Physics

 

[marcus]

I was impressed by this short (11 page) paper by Daly and Djorgovski

http://arxiv.org/astro-ph/0405550
Direct Constraints on the Properties and Evolution of Dark Energy
Ruth A. Daly, S. G. Djorgovski
11 pages, 8 figures, invited presentation from the Observing Dark Energy NOAO Workshop in Tucson

It goes along with Wolram and other's interest in a skeptical appraisal of the dark energy idea.
D and D have developed a method to analyse the raw Supernova data with a minimum of assumptions----not assuming Friedmann equations or concordance model----and calculating the acceleration directly.

then they can say "what assumptions, what model, would get us this observed acceleration?"
in other words they proceed in a non-parametric way. they do not assume there are parameters like dark energy density and negative pressure, and try to find the value of these parameters. they assume nothing like that, they measure the acceleration--redshift relation and then try to find some mechanism that will fit it. then they bring in models, like concordance model, and try them out.

this is in a subtle way more difficult, but it is a commonsense approach,
it is scientifically respectable to work with as few assumptions as you possibly can (and still be able to process the data, get "traction" on the slippery road of the world in other words)

Ruth Daly has 22 papers in arxiv. many of them with Djorgovski.
this was an invited talk at a dark energy conference. She seems to me like
someone to listen to. Djorgovski is at CalTech. maybe Nereid knows of these people
*

 

[marcus]

Here is a 66 page paper by Jonathan Feng
covering the interface between particle physics and cosmology
http://arxiv.org/hep-ph/0405215

"Supersymmetry and Cosmology"

In hep-ph, the ph stands for phenomenology, which studies the testing of theories by observation and measurement.

he describes the current situation where it is cosmology, with
its evidence for dark energy and dark matter----and it 4 percent estimate of the fraction that is baryon-matter. that is driving particle physics and astronomy that is offering prospects for testing various models.

he describes the interface between HEP and astrophysics/cosmology

astroparticle physics, particle astrophysics, whatever
different people call it different things.

he talks about the prospective role of accelerators too, how he thinks it all fits together.

it looks like an attempt at a review paper in a very new area, it is long, careful, with a lot of tables and/or graphs
he's a prominent expert. probably his viewpoint is worth understanding
it is a view of the nearterm future of physics, in some sense

 

[quantumdude]

Straight from Physics Napster:

Astronomy and Cosmology

General:
Added 3/27/03[/color]
Publications of the Astronomical Society of Australia
Added 3/28/03[/color]
http://spaceweb.oulu.fi From Oulu, Finland.
Astronomy Dot Net The name says it all.

Cosmology:
Added 3/27/03[/color]
Cosmological Models From LANL arXiv.

Astrophysics:
Added 3/27/03[/color]
Internal Dynamics of Globular Clusters From LANL arXiv.

Simulators:
Added 3/27/03[/color]
http://www.astronomy.ch/home.html

and...

Relativity

Special Relativity:
Added 3/27/03[/color]
http://www.lassp.cornell.edu/~cew2/P209/P209_home.html
Added 3/28/03[/color]
On the Electrodynamics of Moving Bodies By Einstein, from Fourmilab.
Does the Inertia of a Body Depend on Its Energy Content? By Einstein, from Fourmilab.
Special Relativity by David Hogg—nice book.
Added 7/11/03[/color]
http://astsun.astro.virginia.edu/~jh8h/Foundations/quest7.html Answered by Virginia's Astronomy Department.
http://www.ccinet.ab.ca/tcantine/TP.html

General Relativity:
Added 3/27/03[/color]
Lecture Notes on General Relativity From LANL arXiv.
Added 3/28/03[/color]
http://pancake.uchicago.edu/~carroll/notes by Prof. Sean Carroll, Univ. of Chicago.
Added 7/11/03[/color]
http://www.focusresearch.com/texts/sor-latex.phtml By Einstein.
http://aci.mta.ca/Courses/Physics/4701_97/etext.html From Mount Allison University (in progress).

Other:
Added 3/27/03[/color]
http://www.time-direction.de This could have gone either in the Quantum or Relativity section. I flipped a coin, and here we are.
Added 3/28/03[/color]
Living Reviews in Relativity An online journal.

 

[marcus]

Astrophysics topcites in 2003

Stanford/SLAC puts out lists of topcited articles each year
the 2003 topcites are out
and there is a special review of the Astrophysics list
by Scott Dodelson

http://www.slac.stanford.edu/library/topcites/2003/eprints/astro-ph_review.shtml

 

[marcus]

http://arxiv.org/abs/astro-ph/0406139
A Quantum Approach to Dark Matter
Authors: A. D. Ernest
Comments: To be published in "Progress in Dark Matter Research" Nova Science Inc. New York

"This work develops and explores a quantum-based theory which enables the nature and origin of cold dark matter (CDM) to be understood without need to introduce exotic particles. The quantum approach predicts the existence of certain macroscopic quantum structures that are WIMP-like even when occupied by traditional baryonic particles. These structures function as dark matter candidates for CDM theory on large scales where it has been most successful, and retain the potential to yield observationally compliant predictions on galactic cluster and sub-cluster scales. Relatively pure, high angular momentum, eigenstate solutions obtained from Schrodinger's equation in weak gravity form the structural basis. They have no classical analogue, and properties radically different from those of traditional localised matter (whose eigenstate spectra contain negligible quantities of such states). Salient features include radiative lifetimes that can exceed the age of the universe, energies and 'sizes' consistent with galactic halos, and negligible interaction rates with radiation and macroscopic galactic objects. This facilitates the formation of sparsely populated macroscopic quantum structures that are invisible and stable. Viable structure formation scenarios are based on the seed potential wells of primordial black holes formed at the e+/e- phase transition. The structures can potentially produce suitable internal density distributions and have capacity to accommodate the required amount of halo dark matter. The formation scenarios show that it is possible to incorporate structures into universal evolutionary scenarios without significantly compromising the results of WMAP or the measurements of elemental BBN ratios."

 

[meteor]

Grzegorz Wardziñski offers all the abstracts of the latest papers in Astro-ph in Arxiv, all in the same page. The section is called Astro-ph for busy people. Wonderful!
http://www.camk.edu.pl/~gwar/astro-ph.html

 

[marcus]

turbo points out that Aunt Nettie
has an explanation for why grass is green---
it is trying to get a message back to its home planet.
http://www.dearauntnettie.com/archives/archives-0105.htm
(dont believe this! it may be intended as a joke)

 

[marcus]

Quantum Gravity Phenomenology

http://ws2004.ift.uni.wroc.pl/html.html

WS-2004 symposium, Feb 4-14
notes for all the talks are online, click on "lectures"
for a listing
a number of the talks are also on arxiv. search under author name.

 

[marcus]

Chronos supplied this link
http://www.astrosociety.org/pubs/mercury/31_02/nothing.html
to a non-technical discussion by Filippenko and Pasachoff of
how the universe can have zero total energy
(positive mass-energy of matter balanced by negative gravitational potential)

 

[marcus]

http://astsun.astro.virginia.edu/~jh8h/Foundations/Friedmann.html

sol put this curvegraphing applet link
which is good

but we somehow don't have a good post about the Friedmann eqns.
on this sticky thread and we should. I will try to get something

but please if anybody has a better discussion of the basic equations of cosmology, showing the Lambda which has become so important, please
post it

 

[marcus]

in an earlier post on this thread we had a little bit about the Friedmann eqns. but this is better and also here is a link to a Sean Carroll piece in LivingReviews. the people at Albert Einstein Institute-Potsdam MPI asked Carroll to do the piece on "Cosmological Constant" for LivingReviews

http://relativity.livingreviews.org/Articles/lrr-2001-1/node3.html

Sean Carroll is a blogger as well as one of the worlds foremost cosmologists. he's at chicago. check out his blog sometime--it can be entertaining---the name is "preposterousuniverse"
------------------

In what follows I am using the same notation Sean Carroll uses in
LivingReviews which is pretty standard.

First here is a version of the Friedmann equations which conceals the cosmological constant as "dark energy" added into the rho term as another kind of energy density. So you don't see the Lambda explicitly in this version. This is how a lot of people do it nowadays, and the dark energy fraction is given as 73 percent of total energy density rho.

(\frac{a'}{a})^2 = \frac{8\pi G}{3}\rho - \frac{k}{a^2}

\frac{a''}{a}= -\frac{4\pi G}{3}(\rho + 3p)

Now I'm going to separate the cosmological constant part out as Lamda, an inverse distance squared term. Now rho is all the other stuff, not counting dark energy, and the equations are:

(\frac{a'}{a})^2 = \frac{8\pi G}{3}\rho - \frac{k}{a^2} + \frac{\Lambda}{3}

\frac{a''}{a}= -\frac{4\pi G}{3}(\rho + 3p)+\frac{\Lambda}{3}

EXPLAINING THE NOTATION
this is with c = 1 units, which simplifies things some.
the scale factor of the metric (whose increase is the expansion of the universe) is denoted by the letter a.
k is a spatial curvature parameter used to distinguish three cases
k = -1, 0, +1 for negative curvature, spatially flat, positive curvature

rho is an energy density, and easy to confuse with p pressure

the universe appears to be spatially flat, the critical density rho_crit is that needed for it to be perfectly flat with k = 0

HOW THE HUBBLE PARAMETER COMES IN
the Hubble parameter H is defined to be the time derivative a' of the scale parameter a, divided by a.
H^2 = (\frac{a'}{a})^2
for the time being assume we've included the Lambda term in rho as "dark energy, because this is a convenient way to set things up for calculating stuff, like the critical density. In the case of a spatially flat universe the first Friedmann equation boils down to

H^2 = \frac{8\pi G}{3}\rho_{crit}

algebraically that turns into the formula for the critical density

\rho_{crit} = \frac{3}{8\pi G}H^2

the Hubble parameter has been measured really accurately at 71 km/s per Mpc
and this let's us calculate the critical density at 0.83 joule per cubic km.since the U tests out flat or very nearly so, this is taken to be the
density of all the stuff, stars galaxies, light, dark matter, dust, dark energy etc. It all amounts to 0.83 joule per cubic km.

And the dark energy being 73 percent (from supernova data) means that its share is 0.6 joule per cubic km.

 

[sol2]

sol put this curvegraphing applet link
which is good

but we somehow don't have a good post about the Friedmann eqns.
on this sticky thread and we should. I will try to get something

but please if anybody has a better discussion of the basic equations of cosmology, showing the Lambda which has become so important, please
post it

http://hyperphysics.phy-astr.gsu.edu/hbase/astro/fried.html

This is a good link Marcus as well, and will lead you to many of the equations.

Marcus, part of this journey for me, was recognizng how the universe could move from our past, to our now, and if we could not look beyond to the hyper geometries, how could we have ever accepted any views in cosmology like Reimann's?

What comes next? Omega?

 

[marcus]

Pete contributed this to the "Dark Energy" thread. this shows the cosm. const. Lambda in the context of the full GR equation.
I have usually been discussing this in the simplified context of the Friedmann equations, derived from the full Einstein equation. What Pete has taken the trouble to put in LaTex is a useful reference, so I'll just copy it here:
---exerpt from Pete---
The term Dark Energy is given to that matter which is causing the universe to expand at an accelerating rate. This is what some call "anti-gravity" since this is clearly gravity acting in a repulsive manner.
Back in Einstein's day nobody knew of any kind of matter which could produce such an effect. since Einstein assumed that the universe was static he added a term to his field equations to allow for this repulsive effect. Einstein's equations changed from

G^{\alpha\beta} = \frac{8\pi G}{c^4}T^{\alpha\beta}

to

G^{\alpha\beta} + \Lambda g^{\alpha\beta} = \frac{8\pi G}{c^4}T^{\alpha\beta}

\Lambda is called the cosmological constant. In modern terms the cosmological constant is also called "Dark Energy." This is the term which, for normal matter, allows for anti-gravity when \Lambda > 0...
---endquote---
for full post see
https://www.physicsforums.com/showthread.php?p=30180#post301180

some more links for good measure
http://math.ucr.edu/home/baez/gr/outline1.html
http://math.ucr.edu/home/baez/einstein/einstein.html