First a technical note to avoid mis-understandings.
- Cosmic strings discussed in the article are very different from those of TGD. They are defects in gauge theories at which something - say the phase of Higgs like field becomes ill-defined. Vortex core is analogous to this kind of string: the direction of velocity becomes ill-defined. They carry a very high density of energy.
- In TGD framework cosmic strings are string like objects and correspond to 4-D space-time surfaces which having 2-D string world sheet as projection to M4 factor of H=M4xCP2. Flux tubes are obtained by thickening the 2-D M4 projection to 4-D.
String tension is determined by the value of length scale dependent cosmological constant and by the value of Kähler coupling strength and is for the cosmic strings of the same order of magnitude as for GUT cosmic strings. String tension is roughly proportional to length scale dependent dependent cosmological constant for the flux tubes and behaves like 1/L2(k), where L(k) &protpo; 2k/2 is p-adic length scale. String tension approaches to zero in long length scales.
- In TGD there are also genuine 2-D string world sheets and partonic 2-surfaces identifiable as 2-D singularities of space-time surfaces as minimal surfaces and accompany flux tubes. At number theoretical level they correspond to the singularities of the tangent space for the M8 counterpart of space-time surface at which 4-D quaternionic tangent space reduces to 2-D. They are mapped to singularities of H counterpart of space-time surface by M8-H duality. I will say later something about the nature of these singularities at the level of H.
Could one detect the gravitational waves created by cosmic strings - either GUT strings or cosmic strings in TGD sense?
- Reconnections of cosmic strings are possible both in GUTs and TGD. In GUTs the closed loops decay by emitting gravitational radiation. In TGD framework the monopole flux prevents dissipation of the energy but graviton bursts can be emitted from cusps and kinks of string.
- In TGD framework the periods of thickening for cosmic strings and flux loops transform part of the energy to ordinary matter and also gravitational radiation is generated. Generation of quasars or their predecessors during TGD analog of inflationary period leading from cosmic string dominance to radiation dominated cosmology would give rise to the most intense emission.
- The crucial question whether cosmic strings are still there and if not, what is the radius of the flux tubes determined the p-adic length scale L(k) &propto 21/2. If the radius is too large, there are hopes for the detection of gravitational radiation. The radiation power must be proportional to the square of string tension that is 1/L2(k)&propto 2-2k approaching zero with exponential rate. k=2 could correspond to order of magnitude not far from that for GUT cosmic strings. If ordinary blackhole like entities correspond to k=107 charactering proton and proton Compton length, the power of detecting gravitational radiation from the corresponding flux tubes is exremely low.
- The writhing of cosmic string is the first effect discussed in the popular article. Bullwhip makes a crack-like sound. I understand that the direction of whip must change by almost 180 degrees in writhing - total turning back (I hope I am correct here). Same could happen for cosmic strings but now the motion of string approaching light velocity would replace sound velocity. A signal propagating in single direction would be generated. During the period 2005-2010 LIGO detected no signal. The reason could be that the signal comes only in single direction: they did not have luck.
The TGD counterparts cracks might be very rare if the dynamics allows them at all. In TGD preferred extremal property poses infinite number of additional constraints on the minimal surface solution as a generalization of constraints expressing conformal invariance in string models besides minimal surface property - in fact, the additional condition is that an extremal of 4-D Kaehler action is also in question. All known extremals have this property.
What makes this interesting that for fermionic string world sheets as singularities of 4-D minimal surfaces are proposed to be discontinuities in the direction of tangent space of space-time surface - kind of 2-D fold in 4-D cloth in H=M4xCP2. Also this fold represents total turning back. Writhing would represent a discontinuous tangent for string - a 1-D fold in this 2-D fold: fold inside fold? Can one allows this kind of singularities?
- Second very elegant method relies on the change in the timing of pulsars. The gravitational wave, which can have very low frequency as in case of cosmic strings causes variation of the period of pulsar: gravitational waves cause variation of lengths and this is variation of the period as length of time interval. Hitherto nothing has been observed.
See the article Cosmic string model for the formation of galaxies and stars.
For a summary of earlier postings see Latest progress in TGD.