# [extropy-chat] WMAP Results - Cosmology Makes Sense

Lee Corbin lcorbin at tsoft.com
Tue Mar 21 14:20:24 UTC 2006

Amara writes

> I'll post what I wrote to another list four months ago on that
> dark matter topic. The beginning is a repeat. I should say up
> front that this is 10^{35} scales away from my own field of
> expertise, all of what I know is what I read (when I have time).
> I follow up with a bunch of references from ArXiV (I haven't read
> them all).
>
> The issue is a paper that claims that no exotic dark matter is needed
> to fit the observed rotation curve to a reasonable ordinary matter
> distribution.
>
> In order to distinguish between kinds of dark matter:

Thanks very much for the report!

I did see your earlier version on another list, but I was less interested
in this topic then. I do have more to say about it, but just don't have
time right now, or (sadly) perhaps for a week or so.

Lee

> =================================================================
>
>              CONTENTS of the UNIVERSE
>
>
>
> Type       Likely Composition       Main Evidence     Omega Contrib
> -----------------------------------------------------------------------
>
> Visible      Ordinary matter (protons,     telescopic         0.01
> Matter       neutrons) that forms          observations
>               stars, dust and gas
>
>
> Baryonic     Ordinary matter that is       Big Bang           0.05
> Dark         too dim to see (brown or      nucleosynthesis
> Matter       black dwarfs, massive         and observed
>               compact halo objects:         deuterium abundance
>               MACHOS)
>
>
> Nonbaryonic  Very light "exotic"           Gravity of visible  0.3
> Dark Matter  particles such as             matter is insuffi-
>               axions, neutrinos w/mass      cient to account
>               or weakly interacting         for orbital speeds
>               massive particles:            within galaxies
>               WIMPS                         and galaxies within
>                                             clusters
>
>
> Cosmological Cosmological Constant         Microwave back-     0.?
> Dark Energy  (energy of empty space)       ground suggests
>                                             cosmos is flat but
>                                             there is not enough
>                                             baryonic/nonbaryonic
>                                             matter to make it so.
>
> from [1]
> ================================================================
>
>
> In 1932, Oort found evidence for extra matter within our galaxy, and
> then one year later Zwicky inferred a large density of matter within
> clusters of galaxies. [2]
>
> The conceptual idea is to look at the motions of various kinds of
> astronomical objects, and assess whether the visible material is
> sufficient to provide the inferred gravitational force. If it is not,
> the excess attraction must be due to extra invisible material.
>
> Since the 1970s there has been a discrepancy between the observed
> rotational velocities of stars in the outer regions of spiral galaxies
> and the orbit velocities that one would expect according to Newton's
> Laws from the distribution of visible stars in the galaxy. This
> discrepancy indicates that there should be much more matter in the
> outer parts of the spiral galaxies. [3]
>
> In particular, mass is widely distributed in a galaxy, so then the
> rotation rates of gas and stars should increase with distance from the
> center until most of the galaxy's mass is inside their orbit, then
> slow further out. From Kepler:
>
>                                2
>                               v     G M(R)
>                              ---- = ------
>                               R        2
>                                       R
>
>                                      G M(R)
>                            v  = sqrt(------)
>                                        R
>
> At large distances, enclosing most of the visible part of the galaxy,
> we expect that the rotational velocity to drop off as the square root
> of R. It doesn't. Instead, galactic rotation rates never drop, the
> velocity stays roughly constant. This is evidence that unseen matter
> well beyond the visible disk controls the stars' velocities.  The
> figure that people seem to like that clearly shows this is the
> rotation curve for spiral galaxy NGC 3198, in an article published by
> Albada and Sancisi, 1986.
>
> The Cooperstock and Tieu paper claims that the present solutions to
> the General Relativity equations for this problem for determining
> velocities of stars in galaxies are not correct. General Relativity is
> a difficult equation to solve, so various approximations are usually
> invoked. The present solutions to the distribution of matter in
> galaxies are linear approximations based on perturbation theory where
> the leading terms capture the main characteristics of the problem, and
> the following terms contribute very little, and so the remaining terms
> which would only add unnecessary complexity and are truncated.
> Cooperstock and Tieu claim that a perturbation theory solution is not
> valid because the remaining terms are, instead, large contributors.
>
> However, many disagree, and, according to Sean Carroll, a mathematical
> physicist at the Enrico Fermi Institute, and Kavli Institute for
> Cosmological Physics at the University of Chicago, approximate
> solutions to Einstein's equation are close enough. He says:
>
> 	"But the real reason why most astronomers and physicsts didn't
> 	take the paper seriously is that it violates everything we know
> 	about perturbation theory. In the galaxy, there are two
> 	parameters that are very small - the gravitational potential is
> 	about 10^{-6}, and the velocity of the stars (compared to the
> 	speed of light) is about 10^{-3}. So it would be surprising
> 	indeed if perturbation theory weren't doing a really good job in
> 	this situation, even just including the first-order contribution.
> 	The real reason why nobody paid much attention to Cooperstock and
> 	Tieu is that they didn't even seem to recognize that this was a
> 	problem, much less offer some proposed explanation as to why
> 	perturbation theory was breaking down. Extraordinary claims
> 	require extraordinary evidence, and we would need to be given a
> 	compelling reason to think that our perturbative intuition was
> 	failing before anyone would put a lot of effort into analyzing
> 	this paper." [4]
>
>
> So how were Cooperstock and Tieu solving the problem?
>
> The essense of General Relativity is that 1) Spacetime is a curved
> pseudo-Riemannian manifold with a specific metric and 2) There exists
> a specific relationship between matter and the curvature of spacetime.
> The manifold is four-dimensional and the metric gives a way of taking
> the norm on the manifold, essentially containing all of the
> information about the geometry of the manifold.  [5]
>
> To model the galaxy, Cooperstock and Tieu considered a uniformly
> rotating fluid without pressure and symmetric about its axis of
> rotation in the context of General Relativity.  The exact Einstein
> field solution to their galactic model contains a class of metrics
> called the "van Stockum class of metrics" or the "van Sockum dust" [6]
>
> According to some there are problems with their mathematical
> approach. Sean Carroll says [5] :
>
> 	"To be honest, there are a bunch of problems with this paper. For
> 	example, equations (1) and (2) seem mutually inconsistent - they
> 	have chosen one coordinate system in which to express the
> 	spacetime metric, and another in which to express the spacetime
> 	velocity of the particles in the galaxy. Ordinarily, you have to
> 	pick one coordinate system and stick to it."
>
> Some also find problems with this physical model. Mikolaj Korzynski of
> Warsaw University says [7] that in their model, a gravitational field
> is generated by a thin singular disk in addition to the galaxy matter,
> so the model for this problem is unphysical to their stated goals.
> This extra singular thin disk is moreover made of exotic matter,
> according to another work by Vogt and Letelier [8].
>
> So that is the status as I understand it now. After the references I
> will list alot more references that I dug up on ArXiv that are
> relevant, for all of you to follow up more (and me too, if I have
> time). Cooperstock and Tieu's idea is certainly worthwhile, but I
> don't know if it will pan out (they have not published a rebuttal
> yet), and even if it does, there are other dark matter evidence than
> galactic rotation curves.
>
>
> Amara
>
>
> REFERENCES
>
> [1] "Cosmological Antigravity" by Lawrence M. Krauss in
> Scientific American, Special Edition: The Once and Future Cosmos,
> Volume 12, Number 2, 2002, pg. 33.
>
> [2] Liddle, Andrew, _An Introduction to Modern Cosmology_, 1999,
> Wiley, pg. 62-3.
>
> [3] Hawking, Stephen, _The Universe in a Nutshell_ Bantam, 2001,
> pg. 186-7.
>
> [4]
> http://cosmicvariance.com/2005/10/17/escape-from-the-clutches-of-the-dark-sector/
>
> [5] "A No-Nonsense Introduction to General Relativity"
> http://pancake.uchicago.edu/~carroll/notes/grtinypdf.pdf
> Or see the the fullblown text:
> http://pancake.uchicago.edu/~carroll/notes/
>
> [6]
> http://en.wikipedia.org/wiki/Fluid_solution
> In general relativity, the van Stockum dust is an exact solution of
> the Einstein field equation in which the gravitational field is
> generated by dust particles (*) which are rotating about an axis of
> cylindrical symmetry. Since the density of the dust is increasing with
> distance from this axis, the solution is rather artificial, but as one
> of the simplest known solutions in general relativity, it stands as a
> pedagogically important example. This solution is named for Willem
> Jacob van Stockum, who rediscovered it in 1937, independently of an
> even earlier discovery by Cornelius Lanczos in 1924.
>
> (* Note:  'dust particles' = fluid solution to General Relativity.)
> In general relativity, a fluid solution is an exact solution of the
> Einstein field equation in which the gravitational field is produced
> entirely by the mass, momentum, and stress density of a fluid.
>
> [7] Astrophysics, abstract: http://arxiv.org/abs/astro-ph/0508377
> From: Mikolaj Korzynski
> Date: Wed, 17 Aug 2005 17:27:48 GMT   (4kb)
>
> Singular disk of matter in the Cooperstock and Tieu galaxy model
> Authors: Mikolaj Korzynski
>
>      Recently a new model of galactic gravitational field, based on
>      ordinary General Relativity, has been proposed by Cooperstock and
>      Tieu in which no exotic dark matter is needed to fit the observed
>      rotation curve to a reasonable ordinary matter distribution. We
>      argue that in this model the gravitational field is generated not
>      only by the galaxy matter, but by a thin, singular disk as well.
>      The model should therefore be considered unphysical.
>
> [8] Astrophysics, abstract: http://arxiv.org/abs/astro-ph/0510750
> From: Patricio S. Letelier
> Date: Wed, 26 Oct 2005 19:50:07 GMT   (3kb)
>
> Presence of exotic matter in the Cooperstock and Tieu galaxy model
> Authors: D. Vogt, P. S. Letelier
>
>      We analyze the presence of an additional singular thin disk
>      in the recent General Relativistic model of galactic
>      gravitational field proposed by Cooperstock and Tieu. The
>      physical variables of the disk's energy-momentum tensor are
>      calculated. We show that the disk is made of exotic matter,
>      either cosmic strings or struts with negative energy density.
>
>
> ======================================================================
>
> Search:
> http://xxx.lanl.gov/find/astro-ph/1/abs:+AND+dark+matter/0/1/0/past/0/1
>
>
> "What is the Evidence for Dark Matter?" by J.A. SellwoodSellwood
> http://arxiv.org/abs/ astro-ph/0401398 January 22, 2004
>
> Abstract. Newtonian mechanics indicates that galaxies and galaxy clusters
> are much more massive than we would have guessed from their luminosities,
> with the discrepancy being generally attributed to dark matter
> halos. An alternative hypothesis is that accelerations in very weak
> gravitational
> fields are larger than predicted by Newton's laws, and there is
> no need for dark matter. Even though we do not currently have a satisfactory
> theory associated with this rival hypothesis, we can ask whether
> any observational tests could rule it out or prefer it over the dark matter
> hypothesis. Current evidence suggests that neither hypothesis enjoys a
> decisive advantage over the other. If dark matter turns out to be the correct
> interpretation however, then theories of galaxy formation face some
> quite severe fine-tuning problems.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0510123
>
> From: Paolo Salucci [view email]
> Date: Wed, 5 Oct 2005 14:00:34 GMT   (259kb)
>
> The Distribution of Dark Matter in Spirals
> Authors: Paolo Salucci
> Comments: 6 pages, 5 Fig. Invited Talk at 21st IAP Colloquium." Mass
> Profiles and Shapes of Cosmological Structures", 4-9 July 2005
>
>      In the past years a wealth of observations allowed to unravel the
>      structural properties of the Dark Matter Halos around spirals.
>      First, their rotation curves follow an Universal profile (URC)
>      that can be described in terms of an exponential thin stellar disk
>      and a dark halo with a constant density core, whose relative
>      importance increases with galaxy luminosity. Careful studies of
>      individual objects reveal that dark halos have a core, whose size
>      $r_0$ correlates with the central density $\rho_0$.
>      These properties are in serious discrepancy with the cuspy density
>      distribution predicted by N-body simulations in collisionless
>      $\Lambda$CDM Cosmology.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0506676
>
> From: Paul Frampton [view email]
> Date: Tue, 28 Jun 2005 17:59:05 GMT   (11kb)
>
> Introduction to Dark Energy and Dark Matter
> Authors: Paul H. Frampton
> Comments: 9 pages. Talk at 40th Rencontre de Moriond, La Thuile,
> Italy. March 5-12, 2005
>
>      In an introductory manner, the nature of dark energy is addressed,
>      how it is observed and what further tests are needed to
>      reconstruct its properties. Several theoretical approaches to dark
>      energy will be discussed. Finally, the dark matter, especially
>      WIMPs, is introduced.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0505266
>
> From: Philip D. Mannheim [view email]
> Date (v1): Thu, 12 May 2005 19:15:30 GMT   (150kb)
> Date (revised v2): Mon, 1 Aug 2005 14:53:47 GMT   (155kb)
>
> Alternatives to Dark Matter and Dark Energy
> Authors: Philip D. Mannheim (University of Connecticut)
> Comments: LaTeX, 87 pages, 3 figures. To appear in Progress in
> Particle and Nuclear Physics, 2005. Final version, contains expanded
> references and footnotes
>
>      We review the underpinnings of the standard Newton-Einstein theory
>      of gravity, and identify where it could possibly go wrong. In
>      particular, we discuss the logical independence from each other of
>      the general covariance principle, the equivalence principle and
>      the Einstein equations, and discuss how to constrain the matter
>      energy-momentum tensor which serves as the source of gravity. We
>      identify the a priori assumption of the validity of standard
>      gravity on all distance scales as the root cause of the dark
>      matter and dark energy problems, and discuss how the freedom
>      currently present in gravitational theory can enable us to
>      construct candidate alternatives to the standard theory in which
>      the dark matter and dark energy problems could then be resolved.
>      We identify three generic aspects of these alternate approaches:
>      that it is a universal acceleration scale which determines when a
>      luminous Newtonian expectation is to fail to fit data, that there
>      is a global cosmological effect on local galactic motions which
>      can replace galactic dark matter, and that to solve the
>      cosmological constant problem it is not necessary to quench the
>      cosmological constant itself, but only the amount by which it
>      gravitates.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0504512
>
> From: Jerome Drexler [view email]
> Date: Fri, 22 Apr 2005 22:00:17 GMT   (231kb)
>
> Identifying Dark Matter Through the Constraints Imposed by Fourteen
> Astronomically Based 'Cosmic Constituents'
> Authors: Jerome Drexler (New Jersey Institute of Technology)
> Comments: 19 pages, no figures
>
>      Mankind has not yet explained dark matter, the accelerating
>      expansion of the Universe, the 'knee' and 'ankle' of the cosmic
>      ray energy spectrum graph, the low star formation rates of low
>      surface brightness (LSB) dwarf galaxies, the ignition of hydrogen
>      fusion reactions in the first generation stars or the departing
>      locations of earthbound high-energy cosmic ray protons. A new
>      research hypothesis has been developed by the author based upon
>      finding astronomically based 'cosmic constituents' of the Universe
>      that may be created or influenced by or have a special
>      relationship with possible dark matter candidates. A list of 14
>      relevant and plausible 'cosmic constituents' of the Universe was
>      developed by the author, which was then used to establish a list
>      of constraints regarding the nature and characteristics of the
>      long-sought dark matter particles. A dark matter candidate was
>      then found that best conformed to the 14 constraints established
>      by the 'cosmic constituents.'
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0504422
>
> From: David Merritt [view email]
> Date: Tue, 19 Apr 2005 19:47:40 GMT   (42kb)
>
> Dark Matter Dynamics and Indirect Detection
> Authors: Gianfranco Bertone, David Merritt
> Comments: 17 pages. Invited review for Modern Physics Letters A
> Journal-ref: Mod.Phys.Lett. A20 (2005) 1021
>
>      Non-baryonic, or "dark," matter is believed to be a major
>      component of the total mass budget of the universe. We review the
>      candidates for particle dark matter and discuss the prospects for
>      direct detection (via interaction of dark matter particles with
>      laboratory detectors) and indirect detection (via observations of
>      the products of dark matter self-annihilations), focusing in
>      particular on the Galactic center, which is among the most
>      promising targets for indirect detection studies. The
>      gravitational potential at the Galactic center is dominated by
>      stars and by the supermassive black hole, and the dark matter
>      distribution is expected to evolve on sub-parsec scales due to
>      interaction with these components. We discuss the dominant
>      interaction mechanisms and show how they can be used to rule out
>      certain extreme models for the dark matter distribution, thus
>      increasing the information that can be gleaned from indirect
>      detection searches.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0504422
>
> From: David Merritt [view email]
> Date: Tue, 19 Apr 2005 19:47:40 GMT   (42kb)
>
> Dark Matter Dynamics and Indirect Detection
> Authors: Gianfranco Bertone, David Merritt
> Comments: 17 pages. Invited review for Modern Physics Letters A
> Journal-ref: Mod.Phys.Lett. A20 (2005) 1021
>
>      Non-baryonic, or "dark," matter is believed to be a major
>      component of the total mass budget of the universe. We review the
>      candidates for particle dark matter and discuss the prospects for
>      direct detection (via interaction of dark matter particles with
>      laboratory detectors) and indirect detection (via observations of
>      the products of dark matter self-annihilations), focusing in
>      particular on the Galactic center, which is among the most
>      promising targets for indirect detection studies. The
>      gravitational potential at the Galactic center is dominated by
>      stars and by the supermassive black hole, and the dark matter
>      distribution is expected to evolve on sub-parsec scales due to
>      interaction with these components. We discuss the dominant
>      interaction mechanisms and show how they can be used to rule out
>      certain extreme models for the dark matter distribution, thus
>      increasing the information that can be gleaned from indirect
>      detection searches.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0502118
>
> From: Andrew R. Zentner [view email]
> Date: Sun, 6 Feb 2005 15:24:46 GMT   (46kb)
>
> Dark Matter Halos: Shapes, The Substructure Crisis, and Indirect Detection
> Authors: Andrew R. Zentner (KICP, UChicago), Savvas M. Koushiappas
> (ETH), Stelios Kazantzidis (Zurich, KICP, UChicago)
> Comments: 7 Pages, 3 Figures, Review to appear in The Proceedings of
> the Fifth International Workshop on the Identification of Dark Matter
>
>      In this proceeding, we briefly review three recent results. First,
>      we show that halos formed in simulations with gas cooling are
>      significantly rounder than halos formed in dissipationless
>      $N$-body simulations. The increase in principle axis ratios is
>      $\delta (c/a) ~ 0.2 - 0.4$ in the inner halo and remains
>      significant at large radii. Second, we discuss the CDM
>      substructure crisis and demonstrate the sensitivity of the crisis
>      to the spectrum of primordial density fluctuations on small
>      scales. Third, we assess the ability of experiments like VERITAS
>      and GLAST to detect $\gamma$-rays from neutralino dark matter
>      annihilation in dark subhalos about the MW.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0501231
>
> From: Dirk Puetzfeld [view email]
> Date: Wed, 12 Jan 2005 23:22:02 GMT   (276kb)
>
> Prospects of Non-Riemannian Cosmology
> Authors: Dirk Puetzfeld
> Comments: 5 pages, 3 figures, 22nd Texas Symposium on Rel.
> Astrophysics, Stanford University, December 2004
>
>      In this work we provide the motivation for considering
>      non-Riemannian models in cosmology. Non-Riemannian extensions of
>      general relativity theory have been studied for a long time. In
>      such theories the spacetime continuum is no longer described by
>      the metric alone but endowed with additional geometric quantities.
>      These new quantities can be coupled to the intrinsic properties of
>      matter in a very natural way and therefore provide a richer
>      gravitational theory, which might be necessary in view of the
>      recent cosmological evidence for dark matter and dark energy. In
>      this work we mainly focus on the concepts in metric-affine gravity
>      and point out their possible significance in the process of
>      cosmological model building.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0412297
>
> From: Joseph Silk [view email]
> Date: Mon, 13 Dec 2004 14:14:25 GMT   (23kb)
>
> Dark Matter and Galaxy Formation: Challenges for the Next Decade
> Authors: Joseph Silk
> Comments: To be published in joint proceedings for Mitchell Symposium
> on Observational Cosmology and Strings and Cosmology Conference,
> College Station, April 2004, eds. R. Allen and C. Pope, AIP, New York,
> and in proceedings for PASCOS04/NathFest, Boston, August 2004, eds. G.
> Alverson and M. Vaughan, World Scientific, Singapore
>
>      The origin of the galaxies represents an important focus of
>      current cosmological research, both observational and theoretical.
>      Its resolution involves a comprehensive understanding of star
>      formation, galaxy dynamics, the cosmology of the very early
>      universe, and the nature of the dark matter. In this review, I
>      will focus on those aspects of dark matter that are relevant for
>      understanding galaxy formation, and describe the outlook for
>      detecting the most elusive component, non-baryonic dark matter.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0412195
>
> From: John W. Moffat [view email]
> Date (v1): Wed, 8 Dec 2004 22:20:21 GMT   (105kb)
> Date (revised v2): Mon, 20 Dec 2004 22:02:55 GMT   (106kb)
> Date (revised v3): Thu, 5 May 2005 16:01:46 GMT   (107kb)
>
> Gravitational Theory, Galaxy Rotation Curves and Cosmology without Dark Matter
> Authors: J. W. Moffat
> Comments: 33 pages, 20 figures, 1 table. Latex file. Additional text
> and references. Corrections. To be published in Journal of Cosmology
> and Astroparticle Physics (JCAP)
> Journal-ref: JCAP 0505 (2005) 003
>
>      Einstein gravity coupled to a massive skew symmetric field
>      F_{\mu\nu\lambda} leads to an acceleration law that modifies the
>      Newtonian law of attraction between particles. We use a framework
>      of non-perturbative renormalization group equations as well as
>      observational input to characterize special renormalization group
>      trajectories to allow for the running of the effective
>      gravitational coupling G and the coupling of the skew field to
>      matter. The latter lead to an increase of Newton's constant at
>      large galactic and cosmological distances. For weak fields a fit
>      to the flat rotation curves of galaxies is obtained in terms of
>      the mass (mass-to-light ratio M/L) of galaxies. The fits assume
>      that the galaxies are not dominated by exotic dark matter and that
>      the effective gravitational constant G runs with distance scale.
>      The equations of motion for test particles yield predictions for
>      the solar system and the binary pulsar PSR 1913+16 that agree with
>      the observations. The gravitational lensing of clusters of
>      galaxies can be explained without exotic dark matter. An FLRW
>      cosmological model with an effective G=G(t) running with time can
>      lead to consistent fits to cosmological data without assuming the
>      existence of exotic cold dark matter.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0412059
>
> From: Michael R. Merrifield [view email]
> Date: Thu, 2 Dec 2004 14:43:09 GMT   (36kb)
>
> Dark Matter on Galactic Scales (or the Lack Thereof)
> Authors: M.R. Merrifield (University of Nottingham)
> Comments: 10 pages, 5 figures. Invited review talk presented at
> IDM2004 5th International Workshop on the Identification of Dark
> Matter, Edinburgh, Scotland, September 2004
>
>      This paper presents a brief review of the evidence for dark matter
>      in the Universe on the scales of galaxies. In the interests of
>      critically and objectively testing the dark matter paradigm on
>      these scales, this evidence is weighed against that from the only
>      other game in town, modified Newtonian dynamics. The verdict is
>      not as clear cut as one might have hoped.
>
> ------------------------------
>
> Astrophysics, abstract
> http://arxiv.org/abs/astro-ph/0411503
>
> From: Angele Sene [view email]
> Date (v1): Wed, 17 Nov 2004 16:37:49 GMT   (719kb)
> Date (revised v2): Tue, 18 Jan 2005 18:23:04 GMT   (721kb)
> Date (revised v3): Mon, 28 Feb 2005 16:27:22 GMT   (721kb)
>
> Dark Matter Direct Detection
> Authors: Gabriel Chardin
> Comments: 46 pages, 17 figures, to appear in "Cryogenic Particle
> Detection", edited by Christian Enss, (Springer, Heidelberg, 2005) ;
> one figure and two references modified ; typographical corrections
>
>      Solving the Dark Matter enigma represents one of the key
>      objectives of contemporary physics. Recent astrophysical and
>      cosmological measurements have unambiguously demonstrated that
>      ordinary matter contributes to less than 5 % of the energy budget
>      of our Universe, and that the nature of the remaining 95 % is
>      unknown. Weakly Interacting Massive Particles (WIMPs) represent
>      the best motivated candidate to fill the Dark Matter gap, and
>      direct detection Dark Matter experiments have recently reached
>      sensitivities allowing them to sample a first part of
>      supersymmetric models compatible with accelerator constraints.
>      Three cryogenic experiments currently provide the best
>      sensitivity, by nearly one order of magnitude, to WIMP
>      interactions. With systematic uncertainties far less severe than
>      other present techniques, the next generation of cryogenic
>      experiments promises two orders of magnitude increase in
>      sensitivity over the next few years. The present results,
>      perspectives and experimental strategies of the main direct
>      detection experiments are presented. Challenges met by future
>      ton-scale cryogenic experiments in deep underground sites, aiming
>      at testing most of the SUSY parameter space, are critically
>      discussed.
>
> ------------------------------
>
> General Relativity and Quantum Cosmology, abstract
> http://arxiv.org/abs/gr-qc/0411104
>
> From: Jean-Paul Mbelek [view email]
> Date: Mon, 22 Nov 2004 10:37:08 GMT   (67kb)
>
> Modelling the rotational curves of spiral galaxies with a scalar field
> Authors: J.P. Mbelek
> Comments: Latex, 5 pages with 3 Postscript figures
> Journal-ref: Astron.Astrophys. 424 (2004) 761-764
> DOI: 10.1051/0004-6361:20040192
>
>      In a previous work (Mbelek 2001), we modelled the rotation curves
>      (RC) of spiral galaxies by including in the equation of motion of
>      the stars the dynamical terms from an external real
>      self-interacting scalar field, $\psi$, minimally coupled to
>      gravity and which respects the equivalence principle in the weak
>      fields and low velocity approximation. This model appeared to have
>      three free parameters : the turnover radius, $r_{0}$, the maximum
>      tangential velocity, $v_{\theta max} = v_{\theta}(r_{0})$, plus a
>      strictly positive integer, $n$. Here, we propose a new improved
>      version where the coupling of the $\psi$-field to dark matter is
>      emphasized at the expense of its self-interaction. This
>      reformulation presents the very advantageous possibility that the
>      same potential is used for all galaxies. Using at the same time a
>      quasi-isothermal dark matter density and the scalar field helps to
>      better fit the RC of spiral galaxies. In addition, new
>      correlations are established.
>
> ------------------------------
> --
>
> Amara Graps, PhD      www.amara.com
> Istituto di Fisica dello Spazio Interplanetario (IFSI)
> Istituto Nazionale di Astrofisica (INAF),
> Roma, ITALIA    Amara.Graps at ifsi-roma.inaf.it
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