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A&C reference library

by Phobos
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marcus
#19
Feb1-04, 09:35 PM
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this site seems to have current status of the two rovers
http://marsrovers.jpl.nasa.gov/home/index.html

if you know of a site that's more informative about their status, or the data and pictures they're transmitting, you are most welcome to post it
marcus
#20
Feb2-04, 01:52 PM
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Alan Guth has a couple of recent ones (2003)

"Time since the beginning"
http://arxiv.org/astro-ph/0301199
(quote: "'eternal' inflation...proposes that our universe evolved
from an infinite tree of inflationary spacetime")

"Inflation and cosmological perturbations"
http://arxiv.org/astro-ph/0306275


Stephen Hawking has a recent one (2003)

"Cosmology from the top down"
http://www.arxiv.org/ftp/astro-ph/pa...05/0305562.pdf


Alan Guth has an older, more wide-audience, talk too (2001)

"Eternal Inflation"
http://arxiv.org/astro-ph/0101507

-------------

In eternal inflation an inflating patch expands so fast that even tho the vacuum energy driving it decays exponentially (causing pockets of non-inflating space to form) there is always a larger patch still inflating. Once, by some quantum mechanical accident, this process begins, it must continue forever, and create a welter of pockets of space that have finished inflating.

In a curious way, it appears as if the "eternal" inflation story was invented to take care of the the question of how inflation gets started-----in all spacetime it never has to start more than once (by some no-matter-how-unlikely quantum hiccup) and once started goes on forever making jillions of universes like ours. So the question of how it got started in OUR little universe is dispelled.

If this "starting problem" had never appeared---say the standard models of physics and cosmology had, from the outset, always predicted an inflaton field causing brief exponential expansion and then decaying---then quite possibly no one would have bothered to think up this "eternal" tree of pocket universes outside our own.

Hawking's critique of the "eternal" scenario is an example of someone who disposes of it because he thinks he doesnt need it---he thinks he has a way to describe how what we see came about (without going outside the universe we see).
-------------------

For a mainstream cosmologist's view (simple oneshot inflation, no fancy theory)

Lineweaver
"Inflation and the Cosmic Microwave Background"
http://arxiv.org/astro-ph/0305179
------------------------

Another recent paper (November 2003)

Tsujikawa, Singh, Maartens
"Loop quantum gravity effects on inflation and the CMB"
"Time since the beginning"
http://arxiv.org/astro-ph/0311015

Loop gravity predicts a quantum bounce with a peak density and predicts this will trigger inflation, so no other story is needed about how it gets started. So topic of "eternal" never comes up.
For other papers see references in this one. Tsujikawa and Maartens are string theorists---this is their only contribution so far to Loop gravity---so their examination of the loop gravity mechanism for inflation is especially interesting I think.
marcus
#21
Feb5-04, 12:09 PM
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Wolram supplied a link (in Astrophysics forum) about
an interesting object. It is a spinning black hole that
periodically produces jets along its axis of rotation

http://heasarc.gsfc.nasa.gov/docs/xt...over_0198.html

there are some schematic pictures describing what is going on
and some lightcurves, and an audio soundfile that I havent listened to.
marcus
#22
Feb5-04, 12:35 PM
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http://www.arxiv.org/abs/astro-ph/0402083

this recent article might be a useful source for someone interested
in neutrino astronomy----AMANDA, icecube, the future and an
overall perspective about it.

"High energy neutrino astronomy"
can't think of the author's name just now

Floyd Stecker's article also covers neutrino observation, there's a link to it earlier in the thread
Nereid
#23
Feb6-04, 05:18 PM
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If you are an amateur astronomer (or thinking about it), and are wondering about CCDs, what they can do, how you can use them, etc, I recommend you spend 30 minutes or so reading through the AAVSO* "CCD Observing Manual":
http://www.aavso.org/observing/progr...ndex.shtml#new

This has got to be the best ~30 min intro to the subject on the web.

It covers telescopes, CCDs, computers, software, and (most important for real individuals) the actual time and $$$ that is involved in actually *doing* this stuff!

*despite its name - American Association of Variable Star Observers - it's a truly international non-professional organisation, with an incredibly strong contribution from 'down under' - yah Aussies!
marcus
#24
Feb6-04, 05:55 PM
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thanks Nereid! looking forward to more of your links
on this "reference shelf" thread.
marcus
#25
Feb14-04, 01:18 AM
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This article by Lev Okun has been cited several times IIRC,
most recently by pmb_pby:

http://xxx.lanl.gov/abs/physics/9907017

this is the article about the gravitational redshift.
Lev Okun's 1989 article about the concept of mass
is only available in hard copy AFAIK. If someone knows
where it has been put online please let us know.
marcus
#26
Feb14-04, 09:51 PM
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http://arxiv.org/astro-ph/0402278

Tamara Davis thesis (advisor Charles Lineweaver)
"Fundamental Aspects of the Expansion of the Universe and Cosmic Horizons"

------------------------
http://arxiv.org./abs/astro-ph/0310808

Davis and Lineweaver
"Expanding Confusion:common misconceptions of cosmological horizons and the superluminal expansion of the Universe"

Lineweaver and Davis are at the University of New South Wales.
Lineweaver was one of the leaders of the COBE project (satellite
mapping the cosmic microwave background in the 1990s)
----------------------------
http://arxiv.org./abs/astro-ph/0401024
Lineweaver et al
"The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way"

9 pages, 4 figs. Published in Science, 2 January 2004


We modeled the evolution of the Milky Way to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun.
marcus
#27
Feb18-04, 09:17 AM
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http://nedwww.ipac.caltech.edu/level5/cos_par.html
http://nedwww.ipac.caltech.edu/level5/toc.html
http://nedwww.ipac.caltech.edu/leve...ary/frames.html

"Level 5 knowledgebase for extragalactic astronomy and cosmology"
it has essays on various topics by famous people
and a glossary
it is put together by a CalTech guy
the site has one many awards
and is supported by prestigious funding agencies
arivero reminded me about this site
marcus
#28
Feb19-04, 07:03 PM
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http://micro.magnet.fsu.edu/primer/j...f10/index.html

this java applet goes from a view of the milkyway galaxy down
to subatomic particles in steps of ten
you can control it and back it up if you want
or just let it go

I cant say how this compares to other things like it that
will play on your computer. A friend recommended it.
anyone have other visuals they especially want to recommend?
marcus
#29
Feb24-04, 01:37 PM
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There is a new paper posted by Eric Linder
"Probing Gravitation, Dark Energy, and Acceleration"

http://arxiv.org./astro-ph/0402503

it explores the different explanations of accelerating expansion

cosmological constant (w = -1)
quintessence
some braneworld picture (which he says tends to imply
that w > - 0.7 under realistic assumptions about the density of matter)

he seems fairly sanguine about upcoming possibilities for comparing and distinguishing between models, as the history of the universe's scale-factor becomes a(t) better-known

reputable discussion of the various explanations for acceleration
marcus
#30
Feb26-04, 06:11 PM
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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"
ranyart
#31
Feb27-04, 12:09 AM
P: 368
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
#32
Mar2-04, 11:20 PM
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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...es/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/ajj...gy/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
#33
Mar9-04, 10:17 AM
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http://sci.esa.int/science-e/www/obj...objectid=34567
link courtesy Nereid, see her thread on this
"Osiris, a chthonian planet"
http://www.physicsforums.com/showthr...threadid=13989
Janus
#34
Mar15-04, 07:15 PM
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Here's a nice Ephemeris Generator:

http://ssd.jpl.nasa.gov/cgi-bin/eph
wolram
#35
Mar24-04, 01:12 PM
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http://map.gsfc.nasa.gov/

some major and minor observatories, loads of links and info.
wolram
#36
Mar24-04, 01:33 PM
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http://www.school-for-champions.com/...e/gravity2.htm

gravity equations lots of basic stuff.


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