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Topic: Baryonic matter

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	Baryon - Wikipedia, the free encyclopedia
		Baryons, along with mesons, belong to the family of particles known as hadrons, meaning they are composed of quarks.
		Baryonic matter is matter composed mostly of baryons (by mass), which includes atoms of any sort (and thus includes nearly all matter that we may encounter or experience in everyday life, including our bodies).
		The distinction between baryonic and non-baryonic matter is important in cosmology, because Big Bang nucleosynthesis models set tight constraints on the amount of baryonic matter present in the early universe.
	en.wikipedia.org /wiki/Baryon (547 words)

	baryonic matter (Site not responding. Last check: 2007-10-21)
		The baryons are a family of subatomic particles including the proton, the neutron (collectively called nucleons), and a number of unstable, heavier particles (called hyperons).
		Baryons are strongly interacting fermions, that is, they experience the strong nuclear force and are described by Fermi-Dirac statistics, which apply to all particles obeying the Pauli exclusion principle.
		Baryons have three quarks, whereas mesons have a quark and an antiquark, and thus they are bosonic.
	www.yourencyclopedia.net /Baryonic_matter.html (199 words)

	non-baryonic matter
		Matter that, unlike all the kind kinds of matter with which we are familiar, is not made of baryons (including the neutrons and protons found in all atomic nuclei).
		Therefore, the imprints left by the non-baryonic matter in the cosmic background radiation would be different than those left by the baryonic matter.
		This attribute could be used to measure the contribution of non-baryonic matter to the total amount of mass in the universe.
	www.daviddarling.info /encyclopedia/N/non-baryonic_matter.html (219 words)

	Baryonic dark matter - Wikipedia, the free encyclopedia
		Baryonic dark matter is the dark matter (matter that doesn't emit light) composed of baryons, i.e.
		In the case of big bang nucleosynthesis, the problem is that large amounts of ordinary matter means a denser early universe, more efficient conversion of matter to helium-4 and less unburned deuterium that can remain.
		If one assumes that all of the dark matter in the universe consists of baryons, then there is far too much deuterium in the universe.
	en.wikipedia.org /wiki/Baryonic_dark_matter (189 words)

	Baryonic matter (Site not responding. Last check: 2007-10-21)
		Harvard University: Experimental Soft Condensed Matter The group of David A. Weitz works on the physics of soft condensed matter, materials which are easily deformable by external stresses, electric or magnetic fields, or even by thermal fluctuations.
		Paul Scherrer Laboratory: Department for Condensed Matter Research Large Facilities in Switzerland for the study of solid and liquid condensed matter with Neutron and Muons beams.
		University of Utrecht: Soft Condensed Matter Department Research is focused on the quantitative 3D real-space analysis and manipulation of colloidal structures and processes.
	www.serebella.com /encyclopedia/article-Baryonic_matter.html (366 words)

	Cuspy halo problem - Wikipedia, the free encyclopedia
		The cuspy halo problem arises from cosmological simulations that seem to indicate cold dark matter would form cuspy distributions—that is, increasing sharply to a high value at a central point—in the most dense areas of the universe.
		This is not an intractable problem, however, because the relationships between the baryonic matter's distribution and the dark matter's distribution in areas of high baryonic-matter concentration have not been adequately explored.
		The distribution of baryonic matter, in turn, might affect the cuspy nature of the density profile for dark matter.
	en.wikipedia.org /wiki/cuspy_halo_problem (183 words)

	Baryonic matter (Site not responding. Last check: 2007-10-21)
		In particle physics, the baryons are a familyof subatomic particles including the proton and the neutron (collectively called nucleons), as well as a number of unstable, heavier particles (called hyperons).
		The term "baryon" is derivedfrom the Greek barys, meaning "heavy," as they are heavierthan the other main groups of particles.
		Baryons are strongly interacting fermions —that is, they experience the strong nuclear force and are described by Fermi-Dirac statistics, which apply to all particles obeyingthe Pauli exclusion principle.
	www.therfcc.org /baryonic-matter-31803.html (337 words)

	WMAP Cosmology 101: Matter in the Universe (Site not responding. Last check: 2007-10-21)
		New forms of matter: particle physicists, scientists who work to understand the fundamental forces of nature and the composition of matter, have speculated that there are new forces and new types of particles.
		It is also able to determine some of the properties of the non-baryonic matter: the interactions of the non-baryonic matter with itself, its mass and its interactions with ordinary matter all affect the details of the cosmic microwave background fluctuation spectrum.
		WMAP determined that the universe is flat, from which it follows that the mean energy density in the universe is equal to the critical density (within a 2% margin of error).
	map.gsfc.nasa.gov /m_uni/uni_101matter.html (1033 words)

	Dark matter
		The density of matter in the solar neighborhood is measured by sampling a uniform population of luminous stars that extends well above the disk of the galaxy.
		The dark matter that accounts for the critical density should, at least in the case of some kinds of dark matter, participate in the density fluctuations on large scales.
		Baryonic dark matter does exist: it is far more uncertain whether there exists enough to solve any of the dark matter problems, that is to say, dark matter in galaxy halos, dark matter in galaxy clusters and superclusters, or dark matter in an amount suficient to close the universe.
	astron.berkeley.edu /~mwhite/darkmatter/essay.html (3290 words)

	The Dark Shell (3) Baryonic Matter (Site not responding. Last check: 2007-10-21)
		Since most of the matter in the universe is dark matter, it can be postulated that just prior to the big bang, most of the source was folded dark matter.
		Assuming that the wall of dark matter is stable, then one could assume that at the surface, the dark matter begins to be less dense and that it expands outward away from the wall to its natural limit.
		If most or all of the dark matter in the wall is compressed (at a density comparable to that found within a constraint radius around a baryonic mass), then it must be presumed that it is rather inert and stable -- at least as compared with our universe where it seems to be expanding rapidly.
	www.akilo.com /mayjun2002.html (1238 words)

	Archive of Astronomy Questions and Answers (Site not responding. Last check: 2007-10-21)
		If the fl holes were originally normal matter which formed after this era, then this baryonic component would have been involved in nucleosynthesis and would thereby have affected the cosmic abundances of helium, deuterium and lithium relative to hydrogen.
		In principle, you could hide all of the dark matter in such primordial fl holes, and still have the element abundances yield the result that the baryonic matter is only a few percent of the critical density.
		This would be an interesting solution to this dark matter mystery, but you would have to prove that dark matter is, in fact, in the form of optically silent fl holes, and that these do in fact date from BEFORE the era of nucleosynthesis.
	www.astronomycafe.net /qadir/q2306.html (246 words)

	The Dark Shell (Site not responding. Last check: 2007-10-21)
		Dark matter, in the absence of baryonic matter, tends to expand.
		Dark matter is probably composed of discrete units which can be characterized as having relatively large quantum states which are distributed over a broad spectrum with the shortest quantum lengths being at least several hundred kilometers long, The upper bound may be lengths measured in distances up to a major fraction of a light year.
		As the compactness of the dark matter is largely a function of the proximity of baryonic matter, some surface regions of the wall should be particularly distorted, that is, storm-like, due to the movement and/or lumpiness of the regional baryonic mass.
	www.akilo.com /darkmatter.html (1293 words)

	Dark Matter
		There are many reasons to believe that the universe is full of "dark matter", matter that influences the evolution of the universe gravitationally, but is not seen directly in our present observations.
		The nature of this dark matter, and the associated "missing mass problem", is one of the fundamental cosmological issues of modern astrophysics.
		The difference between cold dark matter and hot dark matter is significant in the formation of structure, because the high velocities of hot dark matter cause it to wipe out structure on small scales.
	csep10.phys.utk.edu /astr162/lect/cosmology/darkmatter.html (890 words)

	What is Dark Matter?
		This is done by connecting the observed He/H ratio of the Universe today to the amount of baryonic matter present during the early hot phase when most of the helium was produced.
		If the early baryon density was low, then it was hard for a proton to find a neutron with which to make helium before too many of the neutrons decayed away to account for the amount of helium we see today.
		And there must be some non-baryonic dark matter to account for the remaining 95% of the matter required to give omega, the mass of the Universe, in units of critical mass, equal to unity.
	math.ucr.edu /home/baez/physics/Relativity/GR/dark_matter.html (810 words)

	More than Meets Eye
		Inflationary theory predicts that the universe is flat--that the average density of matter in the universe exactly equals the critical density required to close the universe.
		Some dark matter may simply be ordinary, or "baryonic" matter made of protons, neutrons and electrons that fails to emit radiation detectable on Earth.
		Scientists estimate that this primordial matter equals or exceeds all of the baryonic matter previously accounted for.
	archive.ncsa.uiuc.edu /Cyberia/Cosmos/MoreMeetsEye.html (750 words)

	Dark Matter: Overview
		Baryonic dark matter candidates that comprise a dark halo of a galaxy or cluster are often called Massive Astronomical Compact Halo Objects, or MACHOs.
		This means that a large amount of baryonic dark matter is transformed into stars as the system evolves, and in Sc and Sd galaxies, the dark matter must be in the form of diluted H and He in order for star formation to occur.
		A possible explanation for why galaxies consist of dark halos surrounding luminous matter relates directly to their formation: Matter (baryonic, but not yet luminous, and non-baryonic) collapses at an overdensity, until it reaches a size where its radius is equal to half its initial radius.
	www.calstatela.edu /faculty/rcarr/a151/darkmtr.html (11408 words)

	Proton decay (Site not responding. Last check: 2007-10-21)
		For a long time, protons were thought to be stable—that the laws of physicswould not allow for a proton (which is baryonic matter) tospontaneously decay into a positron and photons (non-baryonic matter) because of conservation of the baryon number.
		However, it has been recently determined that the predominance of matter over antimatter in the universe is theresult of a very slight imbalance in the ratio that occurred very early in its formation.
		This imbalance was exceptionally small,on the order of 1 in every 10,000 particles, but after most of the matter and antimatter annihilated, what was left over was allthe baryonic matter in our current universe.
	www.therfcc.org /proton-decay-40585.html (368 words)

	3 The Dark Matter Candidates
		This missing baryonic matter is also generally referred to as ``dark matter''.
		Figure 3 illustrates the scale-lengths on which the various dark matter candidates might be significant.
		Figure 3: Possible scale-lengths where different types of dark matter might be present, based on a similar representation which appeared in [30].
	relativity.livingreviews.org /Articles/lrr-2002-4/node6.html (224 words)

	AstroNotes - Mar 1999 - A Fritz Zwicky/Dark Matter Primer (Site not responding. Last check: 2007-10-21)
		Predicted in 1937 that dark matter could be investigated by observing galaxies that acted as gravitational lenses, something that came to pass only in the 1990s.
		Big Bang theories of nucleosynthesis make it highly unlikely that all of the missing dark matter is "regular" baryonic matter (which makes up protons, neutrons, people and astronomy newsletters).
		The neutrino is non-baryonic matter; it weakly interacts with other matter (a neutrino could fly though light-years of lead unimpeded), and is quite abundant (several billion have just zipped through you this past second).
	ottawa.rasc.ca /observers/1999/an9903p7.html (459 words)

	Dark Matter
		Since the majority of the matter that we can see is clumped together into galaxies, the total mass of all the galaxies should be a good indication of the mass of the universe.
		It seems that, no matter which direction astronomers point their telescopes, the light from the center of the galaxies is red shifted.
		Without dark matter, critical density lies somewhere between 0.1 and 0.01, and we live in an open universe.
	home.eclipse.net /~cmmiller/DM (3889 words)

	3.1 Baryonic Dark Matter
		Indeed, if it is assumed that the cluster matter has the same fraction of baryonic matter as the universe as a whole, i.e.
		This naturally leads to the conclusion that there is probably unseen baryonic matter in galaxies, but that it is unlikely to be sufficient to entirely explain the rotation curves.
		To explain all the dark matter with compact objects larger than brown dwarfs would have produced too many heavy elements during their evolution as stars prior to collapse and so these are still excluded as halo baryons in figure 3, at least as far as providing the bulk of the Galactic dark matter.
	relativity.livingreviews.org /Articles/lrr-2002-4/node7.html (405 words)

	Recipes (Site not responding. Last check: 2007-10-21)
		Most cosmological models assume that the total amount of all kinds of matter corresponds to the closure density, the density required to just balance the outward expansion of the universe against the an eventual collapse.
		Although some of the dark matter is believed to be ordinary baryonic matter that simply fails to emit radiation detectable on earth, most is presumed to be in the form of extremely massive, slow-moving particles (cold dark matter) or light-weight particles that move near the speed of light (hot dark matter).
		This radiation field interacts with baryonic matter and must be taken into account when developing more comprehensive models of cosmic evolution.
	archive.ncsa.uiuc.edu /Cyberia/Cosmos/CosmicRecipes.html (311 words)

	Dark baryonic matter
		It is astonishing that it is possible to infer the total density of ordinary baryonic matter from the primordial synthesis of light nuclei
		This is the first evidence of dark matter, the baryonic one which could reside in the MACHO's detected by microlensing that might account for up to one third of the galactic halo, and probably more abundantly in diffuse gas very difficult to detect except in the
		This result, apart from giving evidence that most of baryonic dark matter must be in gaseous form, indicates that there is much more matter of non-baryonic type.
	fisica.usac.edu.gt /public/curccaf_proc/masperi/node3.html (353 words)

	We've looked for baryonic dark matter and failed
		Low luminosity (low mass) stars, M dwarfs, have often been proposed as a dark matter candidate but HST observations show that faint red stars contribute less than 6% of the unseen matter in the galactic halo [7].
		If the dark matter is composed of baryons, then these baryons must be clumped into dense bound objects to evade detection.
		Gerhard and Silk [29] have proposed that the dark matter consists mostly of very dense tiny clouds of molecular gas.
	www.astro.princeton.edu /~dns/MAP/Bahcall/node3.html (589 words)

	Baryonic Dark Matter - Bad Astronomy and Universe Today Forum (Site not responding. Last check: 2007-10-21)
		IF the baryonic dark matter is observed in large enough amounts to account for the rotational dynamics of galaxies, then we cannot say the verified observations are wrong because they do not fit the Big Bang's predictions.
		Until the baryonic matter content hinted at in the above studies is verified, there is no reason to panic about that, but in the end the theory must be consistent with the observations.
		There is a lot of converging evidence for the presence of non-baryonic dark matter, but it would sure be nice if we could detect it more directly (and so independently of these other constructs and their constraints) and have a theoretical description of what the heck it is.
	www.bautforum.com /showthread.php?t=4838&highlight=jensen (5538 words)

	Dark Matter
		A high M/L indicates lots of dark matter, a low M/L indicates that most of the matter is in the form of baryonic matter, stars and stellar reminants plus gas.
		Thus, it is for two reasons that the dark matter problem is important, one to determine what is the nature of dark matter, is it a new form of undiscovered matter?, the second is the determine if the amount of dark matter is sufficient to close the Universe.
		The current observations and estimates of dark matter is that 20% of dark matter is probably in the form of massive neutrinos, even though that mass is uncertain.
	zebu.uoregon.edu /~js/21st_century_science/lectures/lec23.html (1763 words)

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