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Of ‘Braneworlds’ and Nearby Black Holes

We’re familiar with four dimensions, three spatial and one temporal. But is there a fourth dimension to space? If so, it implies a new way of looking at gravity. So say physicists Lisa Randall (Harvard University) and Raman Sundrum (Johns Hopkins), who have offered a mathematical description of how gravity’s actual effects might differ from those predicted by Einstein’s General Theory of Relativity. That fourth spatial dimension follows from the theory these two have developed called the type II Randall-Sundrum braneworld gravity model. It suggests that the universe is a membrane, or ‘braneworld,’ embedded within a much larger universe.

Centauri Dreams admires robust theorizing but has always hoped to see solid observational clues that would make such hypotheses testable. And it may be that one has now emerged, in the hands of Charles Keeton (Rutgers) and Arlie Petters (Duke University), who used the Randall-Sundrum model to predict certain cosmological effects that could provide answers, effects that may be susceptible to testing via satellites scheduled for launch within the next few years.

For the braneworld model would have notable consequences. The hypothesis predicts that small black holes from the early universe — with a mass similar to that of a small asteroid — would have survived to the present. Such objects would be part of the dark matter that seems to pervade the universe, exerting gravitational force but reflecting or emitting no light. General Relativity says that such primordial black holes would have evaporated away by now, so finding them would make the braneworld hypothesis tenable.

It would also change our view of nearby space. For remarkably, if such black holes do exist, they may be close. Says Keeton: “When we estimated how far braneworld black holes might be from Earth, we were surprised to find that the nearest ones would lie well inside Pluto’s orbit.” And Petters makes an even more mind-boggling statement:

“If braneworld black holes form even 1 percent of the dark matter in our part of the galaxy — a cautious assumption — there should be several thousand braneworld black holes in our solar system.”

So the object is to look for the effects that these braneworld black holes would exert on electromagnetic radiation coming to Earth from other galaxies. Any such radiation would be subject to gravitational lensing if it came near a black hole. One good place to start is with gamma ray bursts, whose path would be impeded by a black hole to produce an interference pattern. The scientists have worked out the bright and dark ‘fringes’ in the interference pattern that would result; these would offer information on the characteristics of the black holes, and by inference just might change our notions of space and time.

As to missions, the Gamma-Ray Large Area Space Telescope (GLAST), scheduled for launch next summer, may be able to measure such interference patterns. So here is a case where an exotic theory may actually be put to an observational test, and much sooner than many of us would have thought possible. The paper, which appeared in the May 24 online edition of Phyical Review D, is Keeton and Petters, “Formalism for testing theories of gravity using lensing by compact objects. III: Braneworld gravity,” available here.

Comments on this entry are closed.

  • Eric James May 26, 2006, 23:45

    Well, using the CERN physicist’s own arguments favoring the creation of nano black holes in the LHC:

    The solar system has been around for billions of years. If these things were stable, the planets would have long since collapsed into them.

    In other words, if there are at least thousands and potentially hundreds of thousands of primordial black holes orbiting our sun within Pluto’s orbit, certainly at least one of them would have fallen into each of the outer planets billions of years ago and eaten them.

    Another problem; why don’t they fall into each other?

    On the other hand, might the asteroids have originally been a planet that collapsed around one of these things? Maybe we should look for one in the asteroid belt (BEFORE we make them at CERN).

  • qraal May 27, 2006, 3:22

    Hi All

    The LHC black holes will go bang pretty quickly if they get created at all.

    The brane-world holes will be pretty small – a billion ton black hole is only 3 x 10^-15 metres across, so it would be lucky to swallow a proton, let alone much else.


  • Eric James May 28, 2006, 1:32

    The size of the blackhole’s event horizon isn’t important. What’s important is the size of the gravitational field that attracts other matter. What happens then isn’t that the brane-world blackhole is too small to absorb a proton, but rather the proton is squeezed to fit within the blackhole.

    Another question: Should a LHC nano blackhole be too small to affect an entire particle, what happens to a particle that has part of it’s energy absorbed by a nano blackhole? I would suspect that it collapses around the nano blackhole sending out parton radiation. That is that nano blackholes would be as destructive as proton-proton collisions are, without needing the extreme kinetic energy differentials… basically irradiating matter.

    Of course none of this considers force conservation. Does it apply? It’s supposed to, but it hasn’t been tested yet.

  • Administrator May 28, 2006, 8:34

    The Not Even Wrong weblog offers a highly critical appraisal of coverage of the braneworld story in the popular press (including weblogs like this one) here:


  • Eric James May 28, 2006, 15:33

    Yeah, I looked over those references. Like I wrote earlier, I’ll believe in branes when I see one.

    Note: In the above message I meant particle collisions, proton collisions.

  • Eric James May 28, 2006, 15:34

    Oops that should’ve read “I meant particle collsions, NOT proton collisions.

  • Rusty Roe August 14, 2006, 20:37

    Why is it best to employ gamma rays from gamma-ray-bursts for observational purposes to verify interference patterns of the spectrum? What is magic about gamma rays for these measurements? Why can tests use light from non-gamma ray sources on existing satellites of the GRO or Hubble or Swift variety?

  • Administrator August 19, 2006, 14:33

    Re Rusty’s question above (on gamma ray measurements), I have the following response from Arlie Petters at Duke:

    “The reason is that when we calculated the energy range where the effects of primordial braneworld black holes would show up, we were surprized to find that the range is tens to hundreds of MeV. This lands one right in the gamma ray part of the spectrum … that part of the spectrum which should be accessible to the GLAST satellite. Now, why gamma-ray bursters?

    “Answer: They are excellent pointlike sources of gamma rays and GLAST will be able to study their light profiles. The big hope is that as GLAST catalogues these profiles, one would find the “wiggle” we predicted … namely, the effects a primordial braneworld black hole would produce when lensing the gamma ray light from one of these bursters.”

  • Rusty Roe August 19, 2006, 15:37

    Confirmation Questions:

    1. Determining the existence of the primordial black holes will be accomplished by observing the interference patterns produced as the gamma-rays are bent in a path around the black holes??

    2. Is the objective of finding the primordial black holes designed to add a degree of credibility to the braneworld model?

    3. Assuming the primordial black holes exist in our solar system, what is the expected probability of one of these primordial objects lining-up in the gamma-ray path such that the interference patterns will be observed and recorded by GLAST? On the surface, it looks like this is a relatively remote possibility. I mean, it might be like hunting for a needle in a haystack.

  • Administrator August 22, 2006, 14:33

    Well, I’ll try to answer these questions, though anyone else with more detailed knowledge on this work should feel free to correct me. But yes, the black holes’ existence could be inferred from the gamma-ray studies, and if black holes appear in the numbers suggested, then this would seem to add credibility to the braneworld model, although string theory is so controversial that I don’t know how many other explanations might emerge if that happens.

    Anyway, the probability of black holes lining up precisely as needed is obviously low, which is a test of how frequently they occur — if the survey produces results, it will be taken as an indication that the model is correct.

  • david murray November 10, 2006, 17:04

    Have you thought of the possibility that the cause of a supposed black hole is that the two magnetic poles at either end of a planet or a star could collapse in on itself.

    My theory could be possible because the magnetic forces that hot metal moving fast, create an electric magnetic force that gives us our magnetic north and south poles. I know that not all planets give off a magnetic forces but the ones that do could be potential BLACK HOLES, because the magnetic poles could be strengthened by the heat and energy given off by stars could cause the planet to INPLODE causing a BLACK HOLE.

  • ljk February 27, 2007, 23:27

    Astrophysics, abstract

    From: Laxmikant Chaware [view email]

    Date: Sun, 25 Feb 2007 21:34:59 GMT (26kb)

    Do Black Holes End up as Quark Stars ?

    Authors: R.K.Thakur

    Comments: 6 pages

    The possibility of the existence of quark stars has been discussed by several authors since 1970. Recently, it has been pointed out that two putative neutron stars, RXJ 1856.5 – 3754 in Corona Australis and 3C58 in Cassiopeia are too small and too dense to be neutron stars; they show evidence of being quark stars. Apart from these two objects, there are several other compact objects which fit neither in the category of neutron stars nor in that of black holes. It has been suggested that they may be quark stars.In this paper it is shown that a black hole cannot collapse to a singularity, instead it may end up as a quark star. In this context it is shown that a gravitationally collapsing black hole acts as an ultrahigh energy particle accelerator, hitherto inconceivable in any terrestrial laboratory, that continually accelerates particles comprising the matter in the black hole. When the energy \textit{E} of the particles in the black hole is $\geq 10^{2}$GeV, or equivalently the temperature \textit{T} of the matter in the black holes is $\geq 10^{15}$K, the entire matter in the black hole will be converted into quark-gluon plasma permeated by leptons. Since quarks and leptons are spin 1/2 particles,they are governed by Pauli’s exclusion principle. Consequently, one of the two possibilities will occur; either Pauli’s exclusion principle would be violated and the black hole would collapse to a singularity, or the collapse of the black hole to a singularity would be inhibited by Pauli’s exclusion principle, and the black hole would eventually explode with a mini bang of a sort. After explosion, the remnant core would stabilize as a quark star.


  • ljk May 17, 2007, 14:44

    On Constructing Baby Universes and Black Holes

    Authors: Tanmay Vachaspati

    (Submitted on 15 May 2007)

    Abstract: The creation of spacetimes with horizons is discussed, focussing on baby universes and black holes as examples. There is a complex interplay of quantum theory and General Relativity in both cases, leading to consequences for the future of the universe and the information loss paradox, and to a deeper understanding of quantum gravity.


    Not an “Honorable Mention” in the Gravity Research Foundation Essay Competition


    General Relativity and Quantum Cosmology (gr-qc); Astrophysics (astro-ph); High Energy Physics – Theory (hep-th)

    Cite as:

    arXiv:0705.2048v1 [gr-qc]

    Submission history

    From: Tanmay Vachaspati [view email]

    [v1] Tue, 15 May 2007 17:15:07 GMT (19kb)


  • Walter L. Wagner September 3, 2007, 18:08

    The Large Hadron Collider [LHC]at CERN might create numerous different particles that heretofore have only been theorized. Numerous peer-reviewed science articles have been published on each of these, and if you google on the term “LHC” and then the particular particle, you will find hundreds of such articles, including:

    1) Higgs boson

    2) Magnetic Monopole

    3) Strangelet

    4) Miniature Black Hole [aka nano black hole]

    In 1987 I first theorized that colliders might create miniature black holes, and expressed those concerns to a few individuals. However, Hawking’s formula showed that such a miniature black hole, with a mass of under 10,000,000 a.m.u., would “evaporate” in about 1 E-23 seconds, and thus would not move from its point of creation to the walls of the vacuum chamber [taking about 1 E-11 seconds travelling at 0.9999c] in time to cannibalize matter and grow larger.

    In 1999, I was uncertain whether Hawking radiation would work as he proposed. If not, and if a mini black hole were created, it could potentially be disastrous. I wrote a Letter to the Editor to Scientific American [July, 1999] about that issue, and they had Frank Wilczek, who later received a Nobel Prize for his work on quarks, write a response. In the response, Frank wrote that it was not a credible scenario to believe that minature black holes could be created.

    Well, since then, numerous theorists have asserted to the contrary. Google on “LHC Black Hole” for a plethora of articles on how the LHC might create miniature black holes, which those theorists believe will be harmless because of their faith in Hawking’s theory of evaporation via quantum tunneling.

    The idea that rare ultra-high-energy cosmic rays striking the moon [or other astronomical body] create natural miniature black holes — and therefore it is safe to do so in the laboratory — ignores one very fundamental difference.

    In nature, if they are created, they are travelling at about 0.9999c relative to the planet that was struck, and would for example zip through the moon in about 0.1 seconds, very neutrino-like because of their ultra-tiny Schwartzschild radius, and high speed. They would likely not interact at all, or if they did, glom on to perhaps a quark or two, barely decreasing their transit momentum.

    At the LHC, however, any such novel particle created would be relatively ‘at rest’, and be captured by Earth’s gravitational field, and would repeatedly orbit through Earth, if stable and not prone to decay. If such miniature black holes don’t rapidly evaporate and are produced in copious abundance [1/second by some theories], there is a much greater probability that they will interact and grow larger, compared to what occurs in nature.

    There are a host of other problems with the “cosmic ray argument” posited by those who believe it is safe to create miniature black holes. This continuous oversight of obvious flaws in reasoning certaily should give one pause to consider what other oversights might be present in the theories they seek to test.

    I am not without some experience in science.

    In 1975 I discovered the tracks of a novel particle on a balloon-borne cosmic ray detector. “Evidence for Detection of a Moving Magnetic Monopole”, Price et al., Physical Review Letters, August 25, 1975, Volume 35, Number 8. A magnetic monopole was first theorized in 1931 by Paul A.M. Dirac, Proceedings of the Royal Society (London), Series A 133, 60 (1931), and again in Physics Review 74, 817 (1948). While some pundits claimed that the tracks represented a doubly-fragmenting normal nucleus, the data was so far removed from that possibility that it would have been only a one-in-one-billion chance, compared to a novel particle of unknown type. The data fit perfectly with a Dirac monopole.

    While I would very much love to see whether we can create a magnetic monopole in a collider, ethically I cannot support such because of the risks involved.

    For more information, go to: http://www.LHCdefense.org


    Walter L. Wagner (Dr.)

  • Adam September 3, 2007, 20:33

    Hi Walter

    LHC black-holes will be too small to swallow even a proton let alone the Earth, and even if stable, being uncharged they will escape the collider and probably be ejected from Earth at a substantial fraction of lightspeed due to the recoil of other particles produced by the collision. Earth’s escape velocity for a 1,000 amu mini-hole (where on Earth did you get 10,000,000 from?) is the equivalent of 650 eV – a lot less than expected recoil from decay product ejection.

    Your claims are unnecessary alarmism akin to the brouhaha stirred up by people who opposed the launch of Cassini & its RTGs or the well-meaning people who predicted nuclear detonation of Galileo’s RTGs when it was crashed into Jupiter. You seem sufficiently aware to read the literature so why don’t you, and thus calm your nerves? Besides the Earth collapse time from even a billion ton black hole is many millions of years, so it’s hardly worth dreading such a ridiculously unlikely disaster.

  • Adam September 3, 2007, 21:14

    Hi again

    Assuming a billion ton black-hole has an event horizon as big as a proton (~10E-15 m) and it effectively swallows whole particles as it moves then moving through about 25,600 km of core-density iron (atoms about 10E-10 m apart) with every 30 minute orbit the hole swallows some 10E-8 kg of material. To double in mass and size takes roughly 4.5 quadrillion years. To swallow the planet takes a few multiples of that already gigantic timespan. Making a billion billion-ton black holes reduces the time to the current age of the Earth.

    This is not a disaster by any measure of the word. Humans could disassemble the planet and reassemble it away from the black holes long before they became problematic. In fact the Eddington radiation from introduced black-holes might be how our far, far future descendents choose to warm the planet and drive the magnetic field after radiogenic heating becomes negligible in a few billion years.

  • Adam September 3, 2007, 21:16

    oops… a MILLION billion ton black-holes I meant. Sorry. Calculating in my head.

  • Walter L. Wagner September 6, 2007, 15:39


    Thanks for thinking about the miniature black hole event-horizon, which is quite small, and makes them very un-reactive initially. That’s likely why they’re not a problem when created in nature by rare high-E cosmic rays striking the moon, etc., with the miniature black hole moving through the planetary object at near-light-speed, rarely interacting.

    The larger value for the mass of a mini-black-hole comes from colliding Lead, not Hydrogen. Yes, it is much smaller for the Hydrogen. I did a rough approximation, as well.

    For the RHIC, the Gold-Gold collisions are at sufficient energy [velocity] that their effective mass is increased 1,000-fold. If all that mass were in a miniature black hole [which does not appear to have happened, but who knows], it would be 2 X 197 X 1000, or about 400,000 amu. The LHC is reported to be about 30-fold higher than the RHIC, so about 12,000,000 amu, which I rounded down to 10,000,000 even though Lead is at 207 amu, not 197 like Gold.

    Extensive studies have been done on the residual energies of central collisions. The figures I have seen show that about 14% of the central collision events would then have residual energies of less than 40,000 km/hr [escape velocity]. If you have other studies, I would appreciate references, or your calculations.

    As to the slow rate of accretion of mass, while initially it might be slow [and I came up with the same result on the study of strangelet accretion as well], as the mass increased, the rate of accretion would increase.

    However, the proposal is to create millions of central collisions, hence the LHC has been referred to as a “minature black hole factory”. If these all begin dropping to the center of the earth, each acting independently at first, they would eventually begin to coalesce. While the calculations of the time-dependency for that to occur is difficult, it should not be more than a few years to a few millenia, initially.

    Personally, I would not want to know that we were creating a situation in which our descendants would be FORCED to evacuate our planet because of what we created. What if they’re not more technologicaly advanced than us [for whatever reasons]?



  • Adam September 6, 2007, 18:38

    Hi Walter

    I very much doubt the black-holes will be stable against Hawking radiation – if they form at all. But assuming you are correct the holes will still be much smaller than protons so the time required for proton quarks to tunnel into the event horizon will be quite large. And to coalesce a black-hole as big as a proton will take ~ 10^32 10,000,000 amu black-holes.

    So tell me again why I should worry? A black-hole as big as a proton would fall through the Earth as though it was a vacuum – on average atoms would be about 100,000 proton radii away, thus relatively unperturbed by the passing hole. Only a head-on collision would result in a possible absorption – though even that’s not a sure thing.

    Once the hole is big enough to begin accreting the Eddington radiation produced will cause significant pressure – thus making the flow discontinuous. Things get complicated after that, but such hot-spots would look a lot like present day mantle hot-spots… perhaps Earth is already vanishing down black-holes?

  • Eric James September 7, 2007, 4:18

    Maybe it’s not a good idea to play dice with the earth?

  • ljk December 24, 2007, 2:30

    Cyclic Universes from General Collisionless Braneworld Models

    Authors: E. N. Saridakis

    (Submitted on 28 Oct 2007)

    Abstract: We investigate the full 5D dynamics of general braneworld models. Without making any further assumptions we show that cyclic behavior can arise naturally in a fraction of physically accepted solutions. The model does not require brane collisions, which in the stationary case remain fixed, and cyclicity takes place on the branes. We indicate that the cosmological constants play the central role for the realization of cyclic solutions and we show that its extremely small value on the observable universe makes the period of the cycles and the maximum scale factor astronomically large.

    Comments: 16 pages, 1 figure, submitted for publication to Nucl. Phys. B

    Subjects: High Energy Physics – Theory (hep-th); Astrophysics (astro-ph)

    Cite as: arXiv:0710.5269v1 [hep-th]

    Submission history

    From: Emmanuil Saridakis [view email]

    [v1] Sun, 28 Oct 2007 08:27:41 GMT (43kb)


  • ljk February 7, 2008, 10:27

    Particle Accelerator May Reveal
    Shape Of Alternate Dimensions

    Science Daily Feb. 4, 2008


    When the world’s most powerful
    particle accelerator starts up later
    this year, exotic new particles may
    offer a glimpse of the existence and
    shapes of extra dimensions, claim
    researchers from the University of
    Wisconsin-Madison and the University
    of California-Berkeley. The telltale
    signatures left by a new class of


  • ljk February 7, 2008, 11:57

    A discussion on Cosmic Variance of a paper about
    “hiding” extra dimensions without provoking branes:


  • ljk March 12, 2008, 9:34

    New “Twilight Zone” Dimension Sought

    Like an episode from “Twilight Zone,” scientists are exploring the possibility “that the universe has an imperceptibly small dimension (about one billionth of a nanometer) in addition to the four that we know currently,” according to Michael Kavic, one of the investigators on the project at Virginia Tech. “This extra dimension would be curled up, in a state similar to that of the entire universe at the time of the Big Bang.”

    The team of physicists at Virgina Tech is looking for small primordial black holes created a fraction of a second after the beginning of the universe that, when they explode, may produce a radio pulse that could be detected here on Earth.

    Full article here:


  • ljk November 25, 2008, 14:03

    Cosmic Acceleration and Extra Dimensions

    Authors: Varun Sahni, Yuri Shtanov

    (Submitted on 24 Nov 2008)

    Abstract: Brane cosmology presents many interesting possibilities including: phantom acceleration (w<-1), self-acceleration, unification of dark energy with inflation, transient acceleration, loitering cosmology, new singularities at which the Hubble parameter remains finite, cosmic mimicry, etc. The existence of a time-like extra dimension can result in a singularity-free cyclic cosmology.

    Comments: 10 pages, 3 figures. Invited contribution to “Problems of Modern Cosmology”, special volume commemorating the fiftieth birthday of Prof. S.D. Odintsov

    Subjects: Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Theory (hep-th)

    Cite as: arXiv:0811.3839v1 [astro-ph]

    Submission history

    From: Varun Sahni [view email]

    [v1] Mon, 24 Nov 2008 10:53:33 GMT (47kb)


  • ljk December 24, 2010, 13:27

    Brane Holes

    Authors: Valeri P. Frolov, Shinji Mukohyama

    (Submitted on 21 Dec 2010)

    Abstract: The aim of this paper is to demonstrate that in models with large extra dimensions under special conditions one can extract information from the interior of 4D black holes. For this purpose we study an induced geometry on a test brane in the background of a higher dimensional static black string or a black brane.

    We show that at the intersection surface of the test brane and the bulk black string/brane the induced metric has an event horizon, so that the test brane contains a black hole. We call it a brane hole. When the test brane moves with a constant velocity V with respect to the bulk black object it also has a brane hole, but its gravitational radius r_e is greater than the size of the bulk black string/brane r_0 by the factor (1-V^2)^{-1}. We show that bulk `photon’ emitted in the region between r_0 and r_e can meet the test brane again at a point outside r_e. From the point of view of observers on the test brane the events of emission and capture of the bulk `photon’ are connected by a spacelike curve in the induced geometry. This shows an example in which extra dimensions can be used to extract information from the interior of a lower dimensional black object. Instead of the bulk black string/brane, one can also consider a bulk geometry without horizon.

    We show that nevertheless the induced geometry on the moving test brane can include a brane hole. In such a case the extra dimensions can be used to extract information from the complete region of the brane hole interior. We discuss thermodynamic properties of brane holes and interesting questions which arise when such an extra dimensional channel for the information mining exists.

    Comments: 11 pages, 4 figures

    Subjects: High Energy Physics – Theory (hep-th); General Relativity and
    Quantum Cosmology (gr-qc); High Energy Physics – Phenomenology (hep-ph)

    Report number: Alberta-Thy-14-10, IPMU-10-0219

    Cite as: arXiv:1012.4541v1 [hep-th]

    Submission history

    From: Shinji Mukohyama [view email]

    [v1] Tue, 21 Dec 2010 04:25:13 GMT (98kb)