Wikipedia articles on physics by Chris Hillman who works with John Baez

Critique of Yilmaz theory I agree 100% with Chris Hillman on

Yilmaz theory of gravitation

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The Yilmaz theory of gravitation is an attempt by Huseyin Yilmaz and a handful of coworkers to formulate a classical field theory of gravitation which closely mimics general relativity in weak-field conditions, but in which event horizons cannot appear.

(Orthographic caveat: in Turkish, Yilmaz's name is properly written Hüseyin Yılmaz; we will avoid this spelling because English-speaking readers are likely to misread the ı as i, which could cause technical difficulties. The spelling we use is the one Yilmaz adopts in the arXiv.)

Yilmaz's work has been sharply criticized on various grounds, including the claims that

his proposed field equation is ill-defined,

the two desiderata above are incompatible (event horizons can occur in weak field situations according to gtr, in the case of a supermassive black hole).

Yilmaz vigorously disputes these criticisms. Nonetheless, apart from Yilmaz's own papers, the theory has apparently received no attention in the research literature, apart from two critical papers. Yilmaz claims that his critics have misunderstood him, but it has been suggested that his papers are too murky in crucial places to admit a single clear interpretation. Yilmaz's credibility has also been badly damaged by what appear to be serious misstatements about general relativity.

It is well known that naive attempts to quantize general relativity along the same lines which lead from Maxwell's classical field theory of electromagnetism to quantum electrodynamics fail, and that it has proven very difficult to construct a theory of quantum gravity which goes over to general relativity in an appropriate limit. Yilmaz has claimed that, in contrast, his theory is in some sense 'compatible with quantum mechanics'. He even suggests that it might be an alternative to superstring theory. These claims have apparently been given no credence by physicists other than Yilmaz and a handful of his coworkers.

Yilmaz has offered several descriptions of the alleged field equation for his 'theory', which his critics feel are neither entirely consistent with each other nor well-defined. To understand one of the most basic criticisms of Yilmaz's work, one needs to be familiar with

the statement of the Einstein field equation,

the distinction between coordinate dependent and coordinate independent quantities,

well known facts concerning integration in curved spacetimes,

well known facts concerning gravitational energy-momentum pseudotensors in general relativity.

With this background in hand, one can say that Yilmaz apparently wishes to keep the left hand side of the Einstein field equation (namely the Einstein tensor, which is well defined for any Lorentzian manifold, independent of general relativity) but to modify the right hand side, the stress-energy tensor, by adding a kind of gravitational contribution. According to Yilmaz's critics, this additional term is not well-defined, and cannot be made well defined.

Yilmaz has apparently failed to produce a convincing proposal for an observational or experimental test of his theory, and it would appear that no astronomers have contemplated any attempts to test his ideas. On the other hand, astronomers are very interested indeed in testing theoretically solid competitors of general relativity; see Category:Tests of general relativity.

http://en.wikipedia.org/w/index.php?title=Yilmaz_theory_of_gravitation&oldid=45631271

Polarizable vacuum

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In theoretical physics, particularly fringe physics, polarizable vacuum (PV) refers to a proposal by Harold Puthoff, which has been various characterized as

an attempt to reformulate general relativity in terms of a purely formal analogy with the propagation of light through an optical medium,

an attempt to replace general relativity with a scalar theory of gravitation featuring formal analogies with Maxwell's theory of electromagnetism,

an attempt to unify gravitation and electromagnetism in a theory of electrogravity,

an attempt to provide a physical mechanism for how spacetime gets curved in general relativity, which suggests (to Puthoff) the possibility of "metric engineering" for such purposes as spacecraft propulsion (see Breakthrough Propulsion Physics Program).

Puthoff himself has apparently offered various characterizations of his proposal, which has not been accepted in mainstream physics.

Contents [hide]

1 Related work

2 Puthoff's claims

3 A unified field theory?

4 External links

5 References

Related work

Antecedents of PV and more recent related proposals include the following:

A proposal in 1921 by H. A. Wilson to reduce gravitation to electromagnetism by pursuing the formal analogy between "light bending" in metric theories of gravitation and propagation of light through an optical medium having a spatially varying refractive index. Wilson's approach to a unified field theory is not considered viable today.

An attempt (roughly 1960-1970) by Robert Dicke and Fernando de Felice to resurrect and improve Wilson's idea of an optical analogue of gravitational effects. If interpreted conservatively as an attempt to provide an alternative approach to gtr, rather than as work toward a theory unifying electromagnetism and gravitation, this is not an unreasonable approach, although most likely of rather limited utility.

The 1967 proposal of Andrei Sakharov that gravitation might arise from underlying quantum field theory effects, in a manner somewhat analogous to the way that the (simple) classical theory of elasticity arises from (complicated) particle physics. This work is generally regarded as mainstream and not entirely implausible, but highly speculative, and most physicists seem to feel that little progress has been made.

My work is along the lines of Sakharov 1967.

In a series of papers, Bernard Haisch and Alfonso Rueda have proposed that the inertia of massive objects arises as a "electromagnetic reaction force", due to interaction with the so-called zero point field. According to mainstream physics, their claims rest upon incorrect computations using quantum field theory.

I agree with Hillman's assessment here.

Recent work, motivated in large part by the discoveries of the Unruh effect, Hawking radiation, and black hole thermodynamics, to work out a complete theory of physical analogues such as optical black holes. This is not work toward a unified field theory, but in another sense can be regarded as work towards an even more ambitious unification, in which some of the most famous effects usually ascribed to general relativity (but actually common to many metric theories of gravitation) would be seen as essentially thermodynamical effects, not specifically gravitational effects. This work has excited great interest because it might enable experimental verification of the basic concept of Hawking radiation, which is widely regarded as one of the most revolutionary proposals in twentieth century physics, but which in its gravitational incarnation seems to be impossible to verify in experiments in earthly laboratories.

Uh Oh

The 1999 proposal by Keith Watt and Charles W. Misner of a scalar theory of gravitation which postulates a stratified conformally flat metric of the form

, given with respect to a Cartesian chart, where φ satisfies a certain partial differential equation which reduces in a vacuum region to the flat spacetime wave equation

. This is a "toy theory", not a fully fledged theory of gravitation, since as Watt and Misner pointed out, while this theory does have the correct Newtonian limit, it disagrees with the result of certain observations.

Puthoff's claims

Disputed science:

Polarizable vacuum

Disciplines:

physics

Core tenets:

Gravitation can be described via a scalar theory of gravitation, using a stratified conformally flat metric, in which the field equation arises from the notion that the vacuum behaves like a optical polarizable medium.

Year proposed:

* 1998

Original proponents:

Harold Puthoff, Bernard Haisch

Current proponents:

ditto

In essence, Puthoff proposes that the presence of mass alters the electric permittivity and the magnetic permeability of flat spacetime, εo and μo respectively by multiplying them by a scalar function, K:

εo→ε = Kεo, μo→μ = Kμo

Puthoff argues that this will affect the lengths of rulers made of ordinary matter, so that (he argues), in the presence of a gravitational field, the spacetime metric of Minkowski spacetime is replaced by

where κ2 = K is the so-called "dialetric constant of the vacuum". This is a "diagonal" metric given in terms of a Cartesian chart and having the same stratified conformally flat form in the Watt-Misner theory of gravitation. However, according to Puthoff, κ must satisfy a field equation which differs from the field equation of the Watt-Misner theory. In the case of a static spherically symmetric vacuum, this reduces to

which happens to agree with the analogous situation in the Watt-Misner theory. This yields the asymptotically flat solution

The resulting Lorentzian spacetime has the same weak-field limit (and the same far-field) as the Schwarzschild vacuum solution in general relativity, and it satisfies three of the four classical tests of relativistic gravitation (redshift, deflection of light, precession of the perihelion of Mercury) to within the limit of observational accuracy. However, it yields a different prediction for the inspiral of test particles due to gravitational radiation.

However, requiring stratified-conformally flat metrics rules out the possibility of recovering the weak-field Kerr metric, and is certainly inconsistent with the claim that PV can give a general "approximation" of gtr. In particular, this theory exhibits no frame-dragging effects.

This explains why Puthoff has not been able to describe a rotating source in PV theory.

Also, the effect of gravitational radiation on test particles differs profoundly between scalar theories and tensor theories of gravitation such as general relativity. LIGO is not intended primarily as a test ruling out scalar theories, but is widely expected to do so as a side benefit once it detects unambiguous gravitational wave signals exhibiting the characteristics expected in general relativity.

Ibison has considered a "cosmological solution" of PV, analogous to the Friedmann dust solution (with flat orthogonal hyperslices) in general relativity, and argues that this model is inconsistent with various observational and theoretical constraints. He also finds a rate of inspiral disagreeing with observation, but apparently his result disagrees with that of Watt and Misner (who studied the same Lorentzian manifold in the context of their own scalar theory of gravitation).

It is widely appreciated in physics that, contrary to Puthoff's claims, no scalar theory of gravitation can reproduce all of general relativity's successes. It might be noted that De Felice uses constitutive relations to obtain a susceptability tensor which lives in spatial hyperslices; this provides extra degrees of freedom which help make up for the degree of freedom lacking in PV (and other scalar theories).

A unified field theory?

Ibison feels that Puthoff has never claimed to provide a unified field theory which combines gravitation and electromagnetism. However, Puthoff has coauthored papers with Bernard Haisch which apparently do make this claim, and Puthoff's other papers apparently fail to explicitly disavow any such intention.

In any case, whether or not Puthoff intends any such claim, mainstream physicists agree that PV is

not viable as a unification of gravitation and electromagnetism

not a "reformulation" of general relativity,

not a viable theory of gravitation, since it violates observational and theoretical requirements.

In addition, while this point is presumably moot, Puthoff's arguments for his field equations are highly suspect.

I agree with Hillman's assessment of Puthoff's PV theory 100%.

External links

H. E. Puthoff, M. Ibison, Polarizable Vacuum "Metric Engineering" Approach to GR-Type Effects, MITRE Conference, McLean, VA, May 8, 2003. From the website of EarthTech, a company founded by Puthoff.

References

Visser, Matt (2005). Analog Gravity. Living Reviews in Relativity. Retrieved on 2006-06-02.

Ibison, M. (2003). "Investigation of the polarizable vacuum cosmology." 2003.

Watt, Keith; and Misner, Charles (1999). "Relativistic Scalar Gravity: A Laboratory for Numerical Relativity." 10 Oct 1999.

Puthoff, H. E. (2002). "Polarizable-Vacuum (PV) representation of general relativity". Found. of Phys. 32: 927-943. arXiv eprint

de Felice, F. (1971). "On the gravitational field acting as an optical medium". General Relativity and Gravitation 2: 347-.

Dicke, R. H. (1957). "Gravitation without a principle of equivalence". Reviews of Modern Physics 29: 363-376.

Wilson, H. A. (1921). "An electromagnetic theory of gravitation". Physical Review 17: 54-59.

http://en.wikipedia.org/w/index.php?title=Polarizable_vacuum&oldid=56603531

Stochastic electrodynamics

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Revision as of 23:30, 4 June 2006; Hillman (Talk | contribs)

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In theoretical physics, Stochastic electrodynamics (SED) refers to a more or less controversial theory which posits that the interaction of elementary particles with the vacuum radiation field, or zero point field, is ultimately responsible for various familiar quantum phenonmena.

SED has been developed by a number of physicists; their contributions can generally be characterized as speculative proposals within mainstream physics, but widely popularized work by Haisch and Rueda (especially as portrayed in various cranky websites) is often considered fringe science.

Contents [hide]

1 Brief history

2 Nature of SED

3 The work of Haisch and Rueda

4 Internet culture

5 See also

6 External links

7 References

Brief history

Stochastic electrodynamics is usually credited to Timothy H. Boyer, but builds upon the notions of stochastic optics proposed by T. W. Marshall and the notion of induced gravity proposed by Andrei Sakharov. Boyer's ideas have been further developed by L. de la Pena and A. M. Cetto, who introduced linear stochastic electrodyamics (LSED).

This work is generally regarded as more or less mainstream physics. However, starting in about 1984, Bernard Haisch and Alfonso Rueda, sometimes joined by Harold E. Puthoff, have championed the notion the inertia of a massive object arises via an electromagnetic reaction force via interaction with the so-called zero point field. This builds upon a much earlier proposal by Walther Nernst, but is highly controversial; even more controversial is their proposal that this putative effect can be used for spacecraft propulsion and might even explain the UFO phenomenon.

I agree with Puthoff and Haisch that UFOs are real and need explaining. I do not agree with their explanation.

Nature of SED

The zero point field can be thought of, roughly speaking, as a superposition of electromagnetic waves with random frequencies, phases and directions, with a distribution proportional to the cube of frequency, up to a cutoff frequency on the order of the reciprocal of the Planck time. Planck's constant then appears as a kind of typical amplitude for quantum fluctuations in the zero point field.

The original motivation for SED is that it seeks to provide a local realist foundation for various mysterious effects of quantum field theory, including

Casimir force

van der Waals forces,

diamagnetism

cavity effects

Unruh effect

radiative corrections in the theory of the quantum harmonic oscillator

More controversially, Haisch and Rueda have tried to use SED to provide explanations for the phenomena of

inertia

gravitation

The work of Haisch and Rueda

According to Haisch and Rueda, inertia arises as an electromagnetic drag force on accelerating particles, produced by interaction with the zero-point field. In their 1998 Ann. Phys. paper (see citations), they speak of a "Rindler flux", presumably meaning the Unruh effect, and claim to have computed a nonzero "z.p.f. momentum". This computation rests upon their claim to compute a nonzero "z.p.f. Poynting vector", but according to Bill Unruh this computation is incorrect.

Haisch and Rueda also claim that gravitation arises from an electromagnetic induced dipole shielding similar to the Van der Waals force. They claim to explain the equality of gravitational and inertial mass, which is assumed but not derived in general relativity, and they claim to compute thereby the value of the Planck constant from the gravitational constant, or vice versa.

Haisch and Rueda claim that the structure of atoms arises from a thermal equilibrium between between a particle in a potential well and the zero point field. They claim that this resolves the radiation paradox of the Bohr model, a well known shortcoming of that model. This paradox states that an orbiting classical electron will quickly radiate all its energy away and collapse into the nucleus, which is in drastic disagreement with observation. According to Haisch and Rueda, however, in their theory, each orbiting electron absorbs exactly as much energy from the zero-point field as it radiates. They claim that the absorption and re-emission by the electrons in an atom preserves both the frequency distribution and isotropic random phase character of the zero-point field. They suggest an this intuitive picture: the electron is constantly trying to collapse into the nucleus but is blown off course by "gusts" from the background field and so maintains a stable orbit.

Haisch and Rueda claim that the Heisenberg uncertainty principle also arises from interaction of particles with the zero-point field, which, they say, randomly changes the position and velocity of every particle.

These claims are vigorously disputed by other physicists.

The Haisch/Rueda version of SED appears to incorrectly predict no deflection of light in a gravitational field. Their theory also appears to predict an enormous value for the cosmological constant. Haisch and Rueda propose to solve this problem by assuming that the zero-point field does not itself have gravitational mass; rather, they say, the gravitational mass of a massive object is created by the interaction between this object and the zero-point field. Issues which they have apparently not yet addressed include the homogeneous and isotropic nature of their notion of the zero point field.

Of course this is a serious error in the Haisch-Puthoff theory as the discovery of dark energy accelerating the universe proves. Tensor GCT covariance and equivalence principle imply that virtual quanta gravitate if spin 1/2 and anti-gravitate if spin 1. This follows from w = -1 (neglecting boundary effects) and quantum statistics in 3 + 1 space-time. What happens for anyons in 2 + 1 spacetime in quantum wells with fractional statistics is an interesting question I am thinking about. The world hologram idea is that 2 + 1 space-time is more fundamental than 3 + 1 spacetime.

Internet culture

The proposals of Haisch and Rueda have been eagerly promoted at many websites by new energy fans, who hope that the notion of zero point energy might ultimately provide no cost "energy from the vacuum", thereby solving many current problems in contemporary human society. Others claim that the work of Haisch, Rueda, and Puthoff holds out hope of developing an "inertial-less drive" (see Dean drive) which can be used to enable humans to visit far distant regions of the universe. According to a newstory which appeared in the Washington Post, a paper by Haisch played a key role in the bizarre story of the life-changing encounter of Joe Firmage with a (possibly imaginary) "luminous being".

Yes, this is a true story.

See also

Casimir effect

Polarizable vacuum

Rindler coordinates

Unruh effect

Vacuum energy

Zero-point energy

Andrei Sakharov

Bernard Haisch

Harold E. Puthoff

External links

California Institute for Physics and Astrophysics, a fringe physics organization founded by Bernard Haisch

The CEO from Cyberspace: Joe Firmage, a master of the Universe at 28, Wants to Defy Gravity and Visit the Far Corners Of His Realm, by Joel Achenbach, Washington Post, March 31, 1999, from the anticult website of Rick Ross

H. E. Puthoff, Quantum Vacuum Fluctuations: A New Rosetta Stone of Physics? from Lambert Dolphin's website; Dolphin has claimed that the speed of light has measurably decreased during the past 300 years, that special relativity is incorrect, has promoted the claims of Tom Van Flandern, and so on

References

Marshall, T. W. (1963). "TITLE NEEDED". Proc. Roy. Soc. A: 475.

Sakharov, A. D. (1968). "Vacuum Quantum Fluctuations in Curved Space and the Theory of Gravitation". Sov. Phys. Doklady: 1040.

Boyer, Timothy H. (1975). "Random electrodynamics: The theory of classical electrodynamics with classical electromagnetic zero-point radiation". Phys. Rev.: 790-808.

Boyer, T. H. (1980). "A Brief Survey of Stochastic Electrodynamics". Foundations of Radiation Theory and Quantum Electrodynamics. ISBN 0306402777

Boyer, Timothy H. (1985). "The Classical Vacuum". Scientific American. online version from PADRAK, the website of Patrick Bailey, who publishes New Energy News in Salt Lake City, UT, and who promotes a cranky theory of "plasmoids", which he says "contradict theories about gravity and 'mass' "

Milonni, Peter W. (1994). The Quantum Vacuum: An introduction to quantum electrodynamics. San Diego: Academic Press. ISBN 0-124-98080-5.

Haisch, B.; Rueda, A.; and Puthoff, H. E. (1994). "Inertia as a zero-point-field Lorentz force". Phys. Rev. A: 678-694. on-line version from Haisch's website

de la Pena, L.; and Cetto, A. M. (1996). The Quantum Dice: An Introduction to Stochastic Electrodynamics. Dordrecht: Kluwer. ISBN 0792338189. amazon page

Rueda, Alfonso; and Haisch, Bernard (1998). "Contribution to inertial mass by reaction of the vacuum to accelerated motion". Found. Phys.: 1057-1108. physics/9802030

Rueda, Alfonso, and Haisch, Bernard (2005). "Gravity and the Quantum Vacuum Inertia Hypothesis". Ann. Phys.: 479-498. gr-qc/0504061

de la Pena, L.; and Cetto, A. M. (2005). "Contribution from stochastic electrodynamics to the understanding of quantum mechanics." 4 Jan 2005., a review paper

See Stochastic_electrodynamics/Bibliography for more research papers.

http://en.wikipedia.org/w/index.php?title=Stochastic_electrodynamics&oldid=56907094

to be continued

## Saturday, August 19, 2006

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