Sunday, 4 December 2011
Wednesday, 30 November 2011
No Black Hole In Large Hadronic Collider
\\
arXiv:1111.5830 (*cross-listing*)
Date: Thu, 24 Nov 2011 18:43:30 GMT (38kb)
Title: Any black holes at the LHC?
Authors: Jonas Mureika, Piero Nicolini, Euro Spallucci
Categories: hep-ph gr-qc hep-th
Comments: 10 pages, 1 figure
\\
We introduce analytical quantum gravity modifications of the production cross
section for terascale black holes by employing an effective ultraviolet cut off
$l$. We find the new cross sections approach the usual "black disk" form at
high energy, while they differ significantly near the fundamental scale from
the standard increase with respect to $s$. We show here that the
discontinuous step function used to represent the cross section threshold can
realistically be modeled by two functions representing the incoming and final
parton states in a high energy collision. The growth of the cross section with
collision energy is thus a unique signature of $l$ and number of spatial
dimensions $d$. If these predictions prove to be model-independent, they
suggest black hole formation might be virtually impossible for collision
energies less than 100 TeV. While no such signals would be observed at the LHC,
attention should be focused on ultra-high energy cosmic ray events.
\\ ( http://arxiv.org/abs/1111.5830 ,
arXiv:1111.5830 (*cross-listing*)
Date: Thu, 24 Nov 2011 18:43:30 GMT (38kb)
Title: Any black holes at the LHC?
Authors: Jonas Mureika, Piero Nicolini, Euro Spallucci
Categories: hep-ph gr-qc hep-th
Comments: 10 pages, 1 figure
\\
We introduce analytical quantum gravity modifications of the production cross
section for terascale black holes by employing an effective ultraviolet cut off
$l$. We find the new cross sections approach the usual "black disk" form at
high energy, while they differ significantly near the fundamental scale from
the standard increase with respect to $s$. We show here that the
discontinuous step function used to represent the cross section threshold can
realistically be modeled by two functions representing the incoming and final
parton states in a high energy collision. The growth of the cross section with
collision energy is thus a unique signature of $l$ and number of spatial
dimensions $d$. If these predictions prove to be model-independent, they
suggest black hole formation might be virtually impossible for collision
energies less than 100 TeV. While no such signals would be observed at the LHC,
attention should be focused on ultra-high energy cosmic ray events.
\\ ( http://arxiv.org/abs/1111.5830 ,
Friday, 18 November 2011
Nobel Laureate H. Alfven & Scientific Peer Review
Hannes Alfven (1908-1995) got Nobel in physics in 1970 for his research on Magnetohydrodynamics (MHD). The term ``Alfven Wave'' is widely used in Plasma Physics & Astrophysics. Another term ``Alfven Surface'' is also widely used to denote the surface where the accretion flow around a compact magnetized object (like White Dwarf, Neutron Star/Pulsar) gets stalled due to the magnetic pressure of the central compact object.
Most of the cosmos we know of contain some amount of plasma; and in many cases, the region lying between stars, galaxies or cluster of galaxies is mostly plasma. Accordingly, Alfven proposed that, one must consider the existence of such plasma explicitly even while considering cosmology. In fact, he even wanted to explain many of the large scale structures of the universe by effects (like pinching) of plasma tubes; this was obviously was rather hypothetical. But the point to be noted here is that, his ideas came in conflict with popular cosmological models, and most notably with the Big Bang Paradigm.
So even though, he was a most renowned physicist, his papers arguing for importance of Plasma Physics for cosmology would often be rejected by mainstream journals. In particular, The Astrophysical Journal, whose editor was another would be Nobel Laureate, S. Chandrasekhar, would invariably reject.
``When scientists are specialized, its easy for orthodoxy to develop. The same individuals who formulate orthodoxy theory enforces it by reviewing papers submitted to journals, and grant proposals as well. From this standpoint, I think the Catholic Church was too much blamed in the case of Galileo -- he was just a victim of peer review.''
Most of the cosmos we know of contain some amount of plasma; and in many cases, the region lying between stars, galaxies or cluster of galaxies is mostly plasma. Accordingly, Alfven proposed that, one must consider the existence of such plasma explicitly even while considering cosmology. In fact, he even wanted to explain many of the large scale structures of the universe by effects (like pinching) of plasma tubes; this was obviously was rather hypothetical. But the point to be noted here is that, his ideas came in conflict with popular cosmological models, and most notably with the Big Bang Paradigm.
So even though, he was a most renowned physicist, his papers arguing for importance of Plasma Physics for cosmology would often be rejected by mainstream journals. In particular, The Astrophysical Journal, whose editor was another would be Nobel Laureate, S. Chandrasekhar, would invariably reject.
``When scientists are specialized, its easy for orthodoxy to develop. The same individuals who formulate orthodoxy theory enforces it by reviewing papers submitted to journals, and grant proposals as well. From this standpoint, I think the Catholic Church was too much blamed in the case of Galileo -- he was just a victim of peer review.''
Friday, 4 November 2011
Finding puts brakes on faster-than-light neutrinos: Nature
Published online 20 October 2011 | Nature |
doi:10.1038/news.2011.605
News
An independent experiment confirms that subatomic particles have wrong energy spectrum for superluminal travel.
Dario Auterio's announcement that neutrinos had been seen
moving faster than the speed of light has generated massive interest.Maximilien Brice & Benoit Jeannet , CERN On 17 October, the Imaging Cosmic and Rare Underground Signals (ICARUS) collaboration submitted a paper1 to the preprint server arXiv.org, in which it offered a rebuttal of claims2 to have clocked subatomic particles called neutrinos travelling faster than the speed of light. The original results were published on 22 September by the Oscillation Project with Emulsion-Tracking Apparatus (OPERA) experiment.
Both experiments are based at Gran Sasso National Laboratory near L'Aquila, Italy, and detect neutrinos coming in a beam from CERN, Europe's high-energy particle physics laboratory near Geneva in Switzerland, about 730 kilometres away. Unlike OPERA, ICARUS does not measure the neutrinos' speed directly. Instead, it has shown that the energy spectrum of the neutrinos does not exhibit an effect predicted last month3 by Andrew Cohen and Sheldon Glashow, theoretical physicists at Boston University in Massachusetts.
If the Cohen–Glashow effect is a valid prediction, "neutrinos are not superluminal," says Sandro Centro, a physicist at the University of Padua in Italy, deputy spokesman for ICARUS and a co-author of the latest paper.
Cohen says that an energy spectrum provided by OPERA showed the same inconsistency, and that the spectrum from ICARUS has added to the problem. "There's always value to having things checked independently," says Cohen. "I think it's great ICARUS has done this so quickly."
Too much momentum
The Cohen–Glashow effect is an extension of another phenomenon, well known to physicists. The speed of light travelling through materials such as water is lower than that in a vacuum, and charged particles such as electrons are able to exceed this lower speed when travelling through the medium. When they do, they have excess energy for their momentum and radiate some away in the form of photons, or 'Čerenkov radiation'.Cohen and Glashow concluded that neutrinos travelling faster than light would behave similarly, although as neutral particles they would radiate pairs of electrons and positrons rather than photons. This would reduce the energy of neutrinos travelling long distances.
Such an energy reduction is not seen in the neutrinos from CERN at their destination in Gran Sasso. Indeed, Dario Autiero, a physicist at the Institute of Nuclear Physics in Lyons, France, and OPERA's physics coordinator, says that measurements of the neutrino energies by OPERA, reported in a February 2011 paper4, already failed to show signs of the effect later predicted by Cohen and Glashow. "It is very well known, and it has been presented in tens of OPERA talks at conferences," he says, "it is not something that we learn today because of ICARUS."
Autiero adds that the assumptions made by Cohen and Glashow may not be universally valid. Giacomo Cacciapaglia, a theoretical physicist at King's College London, agrees, saying that not all models of faster-than-light neutrinos have to respect the assumptions of Cohen and Glashow. For example, neutrinos might be able to travel faster than light by taking a shortcut through extra dimensions, in which case they might not radiate.
But Jorge Páramos, a theoretical physicist at the Higher Technical Institute in Lisbon, says that tinkering with the theory in this way is a dangerous game. "It requires you to choose from the available range of theoretical concepts, and could also lead to disagreement with other well established experimental results (not related to the speed of light)," he says.
More than 80 papers have been posted on arXiv discussing OPERA's result. Most try to explain it theoretically, but a small minority claim to find problems. Autiero thinks that despite the huge interest from the public and the media, the debate will have to play out at the normal pace of science, "which is necessarily slow". The experimental work that was the basis for OPERA's claim took almost six years. "Further developments will be quicker but cannot happen on a few days' timescale," he says.
Two experiments are planning to try to test OPERA's measurement of neutrino velocity: the Main Injector Neutrino Oscillation Search (MINOS) experiment based at Fermilab in Batavia, Illinois, and the Tokai to Kamioka (T2K) experiment in Japan. Neither is likely to have results for some months.
-
References
- ICARUS Preprint at http://arxiv.org/abs/1110.3763 (2011).
- OPERA Preprint at http://arxiv.org/abs/1109.4897 (2011).
- Cohen, A. G. & Glashow, S. L. Preprint at http://arxiv.org/abs/1109.6562 (2011).
- OPERA Preprint at http://arxiv.org/abs/1102.1882 (2011).
- This puts at rest the claim that neutrinos can travel faster than light( experiments based at Gran Sasso National Laboratory near L'Aquila, Italy, and detect neutrinos coming in a beam from CERN, Europe's high-energy particle physics laboratory near Geneva), proved by an independent experiment in directly the challenge of Einstein's Special Theory of relativity. When questioning such age old scientific truth,the scientists should have thoroughly studied before making it public with a lot of hype in Scientific and other media.
Tuesday, 1 November 2011
Wikipedia Article Vandalized by some Anonymous editor
Abhas Mitra
Abhas Mitra is a noted Indian astrophysicist and is known for his trait of novel thinking on several frontline astrophysics problems. He is the first astrophysicist to suggest that photo-meson process rather than proton-proton collision process could be the leading mechanism for Ultra High Energy gamma-ray production in ultra-compact X-ray binaries.[1] As far as India based astrophysicists are concerned, he was the first to carry out research on various theoretical aspects of modern Gamma Ray Burst paradigm,[2][3][4][5],.[6] In particular, it was he who first pointed out that the so-called Fireball model may not work unless the presence of an ambient magnetic field, much stronger than the typical interstellar value, would be assumed.[2] Accordingly, he was the first astrophysicist, based in India, who got an oral slot for presentation on the `Theory and Models' of cosmic gamma ray bursts in a prestigious international scientific conference.[7]
One of his recent papers claims to contain an exact mathematical proof that the true/exact Schwarschild Black Holes have zero gravitational mass:
.[8] This paper claims that no objects with a finite gravitational mass can be true/exact black holes. If so, the so-called Black Hole candidates cannot be true black holes even though they may resemble `black holes' in many respects.
.[8] This paper claims that no objects with a finite gravitational mass can be true/exact black holes. If so, the so-called Black Hole candidates cannot be true black holes even though they may resemble `black holes' in many respects.
Recently, Mitra and Norman Glendenning[9] have shown that continued gravitational collapse of massive objects should result in a radiation pressure supported quasi-static hot ball of plasma rather than a true black hole.[10] Such a quasi-static self-gravitating hot ball of plasma has been termed as `Eternally Collapsing Object' in view of the fact it is ever shrinking to asymptotically attain the true Schwarzschild black hole state having M=0.[11]
He may be first author to suggest that some of the unidentified high energy gamma-ray sources detected by the Energetic Gamma Ray Experiment Telescope of NASA are associated with the wind shock of massive Wolf-Rayet stars.[12] And this paper happens to be the only one, written on Indian soil, cited in the science brochure [13] of the space borne latest Fermi Gamma-ray Space Telescope.
Relativistic astrophysicists have struggled for ages to find an exact general relativistic counterpart of the Newtonian Virial theorem :
for a quasi-spherical system. And Mitra found such an exact GR version of Virial Theorem in 2006.[14]
for a quasi-spherical system. And Mitra found such an exact GR version of Virial Theorem in 2006.[14]
Similarly, it has generally been believed that inclusion of fluid pressure increases the Active Gravitational Mass Density in general relativity. However, he has shown that pressure eventually decreases the same and pressure gradient indeed opposes gravitational collapse.[15]
The total energy of the universe, inclusive of matter, radiation and gravitation in the Big Bang has been worked out by Mitra by directly using Einstein's original prescription (i.e., without using any super-potential).[16] This maiden direct computation claims to show that the principle of energy conservation is indeed violated in the Big- Bang model. And only way the principle of energy conservation would be valid here would be if the model would degenerate into a Newtonian one with zero mean matter density!
He has introduced a new astrophysical term - `Einstein - Eddington Time Scale' in the honor of Albert Einstein and Arthur Stanley Eddington. This time scale is based on the fact that in the context of General Relativity, the total available energy of an object in the rest frame of a distant observer is :
, and the maximum rate at which this energy can be radiated out is given by the general relativistic Eddington luminosity. The relevant paper where this concept got developed was selected as one of the highlight publications of Max Planck Society.[17]
, and the maximum rate at which this energy can be radiated out is given by the general relativistic Eddington luminosity. The relevant paper where this concept got developed was selected as one of the highlight publications of Max Planck Society.[17]
Apart from astrophysics, his interest in physics ranges from Classical Mechanics[18] to Quantum Computing.[19]
Although he is basically a theoretical physicist, he evinces keen interest in experimental Gamma-ray Astronomy and is associated with the `Himalayan Gamma Ray Observatory'[20] being set up at Hanle[21] jointly by Tata Institute of Fundamental Research and Bhabha Atomic Research Centre.
He initiated research in Theoretical Astrophysics in Bhabha Atomic Research Centre, India's equivalent of Los Alamos National Laboratory. And he has been heading the Theoretical Astrophysics Section of this premier national research organization since 2004. Presently, he happens to be the lone member of International Astronomical Union from this institute.
In 1989, he won the `Best Young Physicist' Prize from the Indian Physical Society.
See als
Contents |
Reference
- ↑ http://adsabs.harvard.edu/abs/1990A%26A...234L...5M Towards a proper ultra-high-energy gamma-ray production mechanism in Cygnus X-3
- ↑ a b http://adsabs.harvard.edu/abs/1996A%26A...313L...9M Do fireballs in the interstellar medium necessarily imply blast wave propagation?
- ↑ http://adsabs.harvard.edu/abs/1998ApJ...492..677M The Expected Duration of Gamma-Ray Bursts in the Impulsive Hydrodynamic Models
- ↑ http://adsabs.harvard.edu/abs/1998A%26A...340..447M On the true energy budget of GRB970508 and GRB971214
- ↑ http://adsabs.harvard.edu/abs/2000astro.ph.10311M General Relativistic Collapse of Neutron Stars to Strange Stars: A Mechanism for Gamma Ray Bursts
- ↑ http://adsabs.harvard.edu/abs/2000InJPB..74..175M
- ↑ http://www.batse.msfc.nasa.gov/events/3hgrbs/abstracts/models.html 3rd Huntsville Symposium on Gamma-Ray Bursts
- ↑ http://adsabs.harvard.edu/abs/2009JMP....50d2502M Comments on The Euclidean gravitational action as black hole entropy, singularities, and space-time voids [J. Math. Phys. 49, 042501 (2008)
- ↑ http://www-nsdth.lbl.gov/~nkg/
- ↑ http://adsabs.harvard.edu/abs/2010MNRAS.404L..50M Likely formation of general relativistic radiation pressure supported stars or eternally collapsing objects
- ↑ http://www.scitopics.com/Eternally_Collapsing_Object.html Eternally Collapsing Objects
- ↑ http://adsabs.harvard.edu/abs/1997AIPC..410.1271K
- ↑ http://fermi.gsfc.nasa.gov/public/resources/pubs/gsd/GSD_web.pdf GLAST/FERMI Science Brochure
- ↑ http://adsabs.harvard.edu/abs/2006PhRvD..74b4010M Why gravitational contraction must be accompanied by emission of radiation in both Newtonian and Einstein gravity
- ↑ http://adsabs.harvard.edu/abs/2010PhLB..685....8M
- ↑ http://adsabs.harvard.edu/abs/2010GReGr..42..443M Einstein energy associated with the Friedmann-Robertson-Walker metric
- ↑ http://www.mpg.de/english/researchResults/researchPublications/researchReports/AST/200648_084.shtml Max Planck Research Highlights 2006
- ↑ http://adsabs.harvard.edu/abs/1985AmJPh..53.1175M Role of integrals of motion in closing an orbit
- ↑ http://adsabs.harvard.edu/abs/2002PhLA..301..125P
- ↑ http://adsabs.harvard.edu/abs/2005ICRC....5..243K The Himalayan Gamma Ray Observatory
- ↑ http://adsabs.harvard.edu/abs/2008ICRC....3.1361A The Status of Himalayan Gamma Ray Observatory
External links==
- http://in.rediff.com/news/2004/jul/15hawking.htm
- Research Sheds New Light On Quasars (SpaceDaily) July 26, 2006
- http://www.scribd.com/doc/25472637/Brief-Scienti%EF%AC%81c-Career-Outline-of-Abhas-Mitra (Found Mitra's List of Publication in Scribd)
- http://www.nature.com/nindia/2009/090511/full/nindia.2009.130.html (Nature India's News on Mitra's proof that true black holes have zero mass)
- http://hinterland.newsvine.com/_news/2010/04/06/4121434-black-holes-or-balls-of-quark-gluon-plasma (Science News in Nature India: Black Holes or Balls of Quark Gluon Plasma)
- http://www.scribd.com/doc/29170497/akmscincv (CV of Abhas Mitra found on Scribd: Looks quite notable)
Thursday, 20 October 2011
Dark Matter For Non- Experts and Non- Physicists
The matter we are made of and see around us, like, fire, rain, chairs, planets, stars etc. are made of electrons, protons and neutrons. Since they emit/reflect light, heat or other radiations (electromagnetic waves) we can ``see'' them either with naked eye or telescopes or other detectors. Thus, though the air in the room is invisible, it is also a normal matter because we can detect the heat emanating from it by a thermometer or an Infrared Detector. Since most of the mass of such matter is due to protons and neutrons (rather than light electrons) which are collectively called ``Baryons'', normal matter is also referred to as ``Baryonic Matter''.
On the other hand if there would be any matter which do not emit/reflect light, heat (in any form), we would not be able to ``see'', i.e., detect them with either eye, or any telescope. And such a form of HYPOTHETICAL matter would be called as ``DARK MATTER'' (DM).
However all forms of matter, visible or non-visible obey the same laws of Gravitation, they exert mutual gravitation the same way. This simply means that an APPLE will hurtle towards the ground the same way even if it were invisible. Thus even though DM is not visible by eye or telescopes, ITS EFFECT CAN BE FELT through its gravitational interaction. In other words ``Gravitational Mass'' of both Normal Matter and Dark Matter can be found on equal footings.
And when astronomers do their measurement of say a distant Galaxy Cluster, they try to measure both the (i) Amount of Visible Matter, by direct observations as well as (ii) Gravitational Mass, by indirect ways, in the framework of certain theories .
And they often find that:
``The Gravitational Mass is Much LARGER Than The Visible Mass''
In this way, astronomers have inferred the presence of UNSEEN Matter or ``Dark Matter'' in many Galaxy Clusters and even in the outer reaches of our own galaxy called ``Milky Way''.
----------------------------------------
WHAT COULD BE THE NATURE OF THE ``DARK MATTER''?
DM could comprise some elementary particles which hardly interact with normal matter. One such particle is ``Neutrino''; every moment thousands of neutrinos are passing through our body, yet we do not feel any pain or any effect because they do not interact with our eye, nerve, or tissues made of electron, proton and neutron. However, originally, it was believed that neutrinos have no mass just like light quanta (photons) have no mass. Then it was hypothesized that neutrinos may have a tiny mass may be 0.001% of electron mass. With such a tiny mass, neutrinos would still be very agile and move with a speed close to that of light.
Such FAST & AGILE neutrinos would constitute what is known as
``HOT DARK MATTER'' (HDM)
In fact even up to 1980, most of the cosmologists thought that they require just such HDM, and may be just neutrinos.
But soon it became clear that in order that various cosmic structures, like Galaxy Clusters, Super Clusters etc. could form in a relatively short span of the Universe (as per the Big Bang HYPOTHESIS/ASSUMPTION of the origin of the Universe, the DM particles should be heavy & sluggish. And thus came the concept of
COLD DARK MATTER (CDM)
Here the elementary particles constituting DM should be much more massive, say 10-100 times as massive as Protons and move sluggishly with a speed negligible compared to the speed of light. Simultaneously, such particles should be entirely different from protons or neutrons. And scores of big experiments world over have FAILED TO DETECT ANY SUCH FICTITIOUS PARTICLE! It was hoped that the Large Hadron Collider (LHC: Hadron =Heavy Particle) should finally be able to create and detect them. But LHC TOO HAS FAILED TO FIND ANY SUCH EXOTIC PARTICLES!
And now observations on two close by small galaxies, which were supposed to be the best hosts for such CDM show that they may not have any such CDM made of exotic elementary particles!
The finding goes completely against the current cosmological models, which suggest that dark matter should be clustered at the centers of galaxies.
"After completing this study, we know less about dark matter than we did before. Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies," said Matt Walker, the study's lead author.
This may be considered as a big set back for the Big Bang Paradigm as its predictions go haywire.
---------------------------------------------
COULD THERE BE OTHER FORMS OF ``COLD DARK MATTER''
The two above forms of DM are non- baryonic because the elementary particles constituting them are intrinsically different from the social/interacting normal matter.
But, in principle, CDM may comprise, planets and very tiny cold and faint stars called ``Brown Dwarfs''. This is so because they have no light of their own and astronomers are rarely able to ``see'' them. For example, the maiden planet outside the solar system got detected (not seen) may be in 1994!
Also, some physicists claim that CDM is nothing but extremely cold interstellar clouds of Hydrogen Molecules, which hardly emit any radiation. In fact, such cold hydrogen could be so cold that it would be in SOLID form!
Note, although such form of CDM would be invisible, they are made of Normal Matter; i.e., electrons, protons and neutrons.However Big Bang Model requires Exotic Non-normal Cold Dark Matter.
----------------------------------------
COULD ``Dark Matter'' BE ONLY AN ILLUSION?
Some physicists claim that actual law of gravity used to infer the ``Gravitational Mass'' could in subtle error; i.e., as if one overestimates the ``mass'' of the falling APPLE by an incredibly small amount. Although such claimed overestimation must be negligible for the apple, it can be significant on galactic or cosmic scales. Thus as per some physicists, there is actually no unseen/dark matter.
On the other hand if there would be any matter which do not emit/reflect light, heat (in any form), we would not be able to ``see'', i.e., detect them with either eye, or any telescope. And such a form of HYPOTHETICAL matter would be called as ``DARK MATTER'' (DM).
However all forms of matter, visible or non-visible obey the same laws of Gravitation, they exert mutual gravitation the same way. This simply means that an APPLE will hurtle towards the ground the same way even if it were invisible. Thus even though DM is not visible by eye or telescopes, ITS EFFECT CAN BE FELT through its gravitational interaction. In other words ``Gravitational Mass'' of both Normal Matter and Dark Matter can be found on equal footings.
And when astronomers do their measurement of say a distant Galaxy Cluster, they try to measure both the (i) Amount of Visible Matter, by direct observations as well as (ii) Gravitational Mass, by indirect ways, in the framework of certain theories .
And they often find that:
``The Gravitational Mass is Much LARGER Than The Visible Mass''
In this way, astronomers have inferred the presence of UNSEEN Matter or ``Dark Matter'' in many Galaxy Clusters and even in the outer reaches of our own galaxy called ``Milky Way''.
----------------------------------------
WHAT COULD BE THE NATURE OF THE ``DARK MATTER''?
DM could comprise some elementary particles which hardly interact with normal matter. One such particle is ``Neutrino''; every moment thousands of neutrinos are passing through our body, yet we do not feel any pain or any effect because they do not interact with our eye, nerve, or tissues made of electron, proton and neutron. However, originally, it was believed that neutrinos have no mass just like light quanta (photons) have no mass. Then it was hypothesized that neutrinos may have a tiny mass may be 0.001% of electron mass. With such a tiny mass, neutrinos would still be very agile and move with a speed close to that of light.
Such FAST & AGILE neutrinos would constitute what is known as
``HOT DARK MATTER'' (HDM)
In fact even up to 1980, most of the cosmologists thought that they require just such HDM, and may be just neutrinos.
But soon it became clear that in order that various cosmic structures, like Galaxy Clusters, Super Clusters etc. could form in a relatively short span of the Universe (as per the Big Bang HYPOTHESIS/ASSUMPTION of the origin of the Universe, the DM particles should be heavy & sluggish. And thus came the concept of
COLD DARK MATTER (CDM)
Here the elementary particles constituting DM should be much more massive, say 10-100 times as massive as Protons and move sluggishly with a speed negligible compared to the speed of light. Simultaneously, such particles should be entirely different from protons or neutrons. And scores of big experiments world over have FAILED TO DETECT ANY SUCH FICTITIOUS PARTICLE! It was hoped that the Large Hadron Collider (LHC: Hadron =Heavy Particle) should finally be able to create and detect them. But LHC TOO HAS FAILED TO FIND ANY SUCH EXOTIC PARTICLES!
And now observations on two close by small galaxies, which were supposed to be the best hosts for such CDM show that they may not have any such CDM made of exotic elementary particles!
The finding goes completely against the current cosmological models, which suggest that dark matter should be clustered at the centers of galaxies.
"After completing this study, we know less about dark matter than we did before. Our measurements contradict a basic prediction about the structure of cold dark matter in dwarf galaxies," said Matt Walker, the study's lead author.
This may be considered as a big set back for the Big Bang Paradigm as its predictions go haywire.
---------------------------------------------
COULD THERE BE OTHER FORMS OF ``COLD DARK MATTER''
The two above forms of DM are non- baryonic because the elementary particles constituting them are intrinsically different from the social/interacting normal matter.
But, in principle, CDM may comprise, planets and very tiny cold and faint stars called ``Brown Dwarfs''. This is so because they have no light of their own and astronomers are rarely able to ``see'' them. For example, the maiden planet outside the solar system got detected (not seen) may be in 1994!
Also, some physicists claim that CDM is nothing but extremely cold interstellar clouds of Hydrogen Molecules, which hardly emit any radiation. In fact, such cold hydrogen could be so cold that it would be in SOLID form!
Note, although such form of CDM would be invisible, they are made of Normal Matter; i.e., electrons, protons and neutrons.However Big Bang Model requires Exotic Non-normal Cold Dark Matter.
----------------------------------------
COULD ``Dark Matter'' BE ONLY AN ILLUSION?
Some physicists claim that actual law of gravity used to infer the ``Gravitational Mass'' could in subtle error; i.e., as if one overestimates the ``mass'' of the falling APPLE by an incredibly small amount. Although such claimed overestimation must be negligible for the apple, it can be significant on galactic or cosmic scales. Thus as per some physicists, there is actually no unseen/dark matter.
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