Searching for Tachyons (continued)
Gravity and Superstrings
In the final portion of the chapter on tachyons, Tiwari writes: "Recent advances in tachyon physics (in the theoretical domain) originate in quantum electrodynamics in the presence of gravity, and tachyons in superstring theories. Faster-than-light photon propagation due to vacuum polarization effects in a background gravitational field was discovered by Drummond and Hathrell in 1980 [Citation: Physical Review D, #22, page 343.]. On the other hand tachyons have been known to arise from early times in bosonic
strings -- both closed and open; their importance in recent years has been due to the developments in the brane theory and non-perturbative techniques in string theory."
He then explains superluminal photons (based on the given citation), noting that the framework that results from combining Quantum Electrodynamics (QED) and STR "has been very successful" at explaining the electromagnetic interactions among subatomic particles, but that attempts to incorporate the General Theory of Relativity (GTR) [i.e., the curvature of space caused by gravity], "is plagued by insurmountable difficulties." Yet, after going into some of the details of the associated research, which included the study of vacuum polarization subjected to the curved geometry of GTR, Tiwari quotes the researchers as stating that "either perturbative QED is inadequate as a theory when extended to a general-relativistic background, or that photons indeed can travel faster-than-light." Huge implications for cosmologists would therefore stem from the later. But Tiwari also points out: "That vacuum polarization leads to photon velocity exceeding the velocity of light in the early times of the evolution of the universe in a rather intriguing way agrees with the time-varying velocity of light hypothesis in some models of cosmology." This includes his own theory, and Inflation Theory. And "we note that not just photons, neutrinos also become superluminal ...", in such models.
On the other hand, after labeling superluminal photons as "quasi-photons", he cautions that such a photon "should not be interpreted as a tachyon." [Note that part of Tiwari's suggestion that we re-evaluate our concept of time depends on whether or not lightspeed varies with time.] From there, he gets into string theory, noting that QED is a point field-theory, in which the path of a particle establishes a "world-line" in space, while strings are one-dimensional objects that sweep out "world-sheets" as they move through space; thus resulting in those branches of string theory called "brane theory" (i.e., membrane theory) and its close but older relative "superstring theory". He then gives a concise overview of the most important aspects of string theory, and how tachyons are involved; noting that the dynamics of tachyons "may provide useful insight into non-perturbative features of superstrings", leading to "an optimal formulation of the theory."
For my part, I accept that string theories, especially their latest incarnation, brane theory, provide deeper understanding of natural processes than can be had from other theories taken without them, but there is simply too much empirical support for the point-particle descriptions associated with subatomic interactions to completely abandon them.
It seems to me that brane theory and quantum mechanics are actually compatible, if they are kept distance specific. Quantum mechanics, for instance, allows us to study all of the subatomic particles down to distances on the order of the Planck length, while brane theory lets us see what reality is like at smaller distances. The two scenarios need not be at odds, nor should one be abandoned in favor of the other too regularly, while yet other ideas are entertained, as necessary for completeness. In that case, since brane theory involves an inherent prediction of tachyonic objects (FTL strings), at sub-Planck-length distance scales, and therefore asks for the acceptance of such objects by the mainstream physics community, then these objects can and should likewise be regarded as possibly manifesting themselves as point-like tachyons at distances larger than the Planck length; most especially in a Lorentzian relativistic, rather than Einsteinian relativistic, format.
Among those point-like tachyons, I am convinced (though Tiwari does not mention the notion in his book) that there is a kind which explains quantum gravity better than any other hypothetical particle suggested to be responsible for the warping of space caused by gravity, described by the "field equations" of GTR -- which tachyon I have explained thoroughly in my thesis. I am, however, willing to concede that such tachyons may be string-like, or, more correctly, may have string-like substructures, when viewed at distances smaller than the Planck length. [An example substructure would be a string that is spiral shaped, and spins in such a way as to drill through space, like a corkscrew; thus providing an action that pulls towards the source, without causing damage.]
Studying Tiwari's book has, in fact, done much to strengthen the conviction that my thesis is valid, because I find in the book no unbiased theory to refute it, and find therein, as well, a great store of reliable information supporting the conclusion that tachyons, of many kinds, probably do exist.
Based on that conviction, and on "faith" in the open-minded researchers actively engaged in the investigation of superluminal phenomena, I predict that a point-like tachyon will be "discovered" someday, and soon thereafter it will be confirmed, beyond doubt, that the contention I and a growing number of other thinkers have been presenting for a while now must be viewed as a scientific fact, instead of science- fiction. Namely, that gravity is faster-than-light, and may actually involve a tachyonic force quantum-unit.
[End of article.]