arXiv subjects

Dimitri V. Nanopoulos

Publications and source records attributed to Dimitri V. Nanopoulos.

150 records · Page 9Linked to original sources

arXiv2005

Robust Limits on Lorentz Violation from Gamma-Ray Bursts

We constrain the possibility of a non-trivial refractive index in free space corresponding to an energy-dependent velocity of light: c(E) \simeq c_0 (1 - E/M), where M is a mass scale that might represent effect of quantum-gravitational space-time foam, using the arrival times of sharp features observed in the intensities of radiation with different energies from a large sample of gamma-ray bursters (GRBs) with known redshifts. We use wavelet techniques to identify genuine features, which we confirm in simulations with artificial added noise. Using the weighted averages of the time-lags calculated using correlated features in all the GRB light curves, we find a systematic tendency for more energetic photons to arrive earlier. However, there is a very strong correlation between the parameters characterizing an intrinsic time-lag at the source and a distance-dependent propagation effect. Moreover, the significance of the earlier arrival times is less evident for a subsample of more robust spectral structures. Allowing for intrinsic stochastic time-lags in these features, we establish a statistically robust lower limit: M > 0.9x10^{16} GeV on the scale of violation of Lorentz invariance.

astro-ph↗

arXiv2005

Theory and Experiments on the "Quantum Mind"

This article is a short summary, in Greek, of work presented in English in the following articles: 1. Mershin et al. "Towards Experimental Tests of Quantum Effects in Cytoskeletal Proteins" (physics/0505080) 2. Mershin et al. "Learning and Memory deficits Upon TAU Accumulation in Drosophila Mushroom Body Neurons", Learning & Memory 11: 277-287 (2004)

physics.bio-ph↗

arXiv2005

Towards Experimental Tests of Quantum Effects in Cytoskeletal Proteins

It has become increasingly evident that fabrication of novel biomaterials through molecular self-assembly is going to play a significant role in material science and possibly the information technology of the future. Tubulin, microtubules (MTs) and the cytoskeleton are dynamic, self-assembling systems and we asked whether their structure and function contain the clues on how to fabricate biomolecular information processing devices. Here we review our neurobiological studies of transgenic Drosophila that strongly suggest the microtubular cytoskeleton is near the 'front lines' of intracellular information manipulation and storage. We also establish that spectroscopic techniques such as refractometry, surface plasmon resonance sensing and dielectric spectroscopy, coupled with molecular dynamic simulations and (quantum) electrodynamic analytical theory are useful tools in the study of the electrodynamic and possible quantum effects in cytoskeletal proteins. Implicit in our driving question is the possibility that if tubulin and MTs can indeed be cast as the basis of a classical or quantum computer, then perhaps nature has already done so and tubulin and MTs already play such a role in living neural and other cells. If quantum mechanics is found to be important in cellular function (through its involvement in proteins) it is natural to ask whether there are indeed quantum effects pertinent to consciousness. We conclude this work by suggesting a number of ways towards experimentally testing this "Quantum Consciousness Idea" (QCI), directly at the protein level.

physics.bio-ph↗

arXiv2004

Tubulin dipole moment, dielectric constant and quantum behavior: computer simulations, experimental results and suggestions

We used computer simulation to calculate the electric dipole moments of the alpha and beta tubulin monomers and dimer and found those to be |palpha|=552D, |pbeta|=1193D and |palpha-beta|=1740D respectively. Independent surface plasmon resonance (SPR) and refractometry measurements of the high-frequency dielectric constant and polarizability strongly corroborated our previous SPR-derived results giving delta-n/delta-c ~1.800x10^-3 ml/mg. The refractive index of tubulin was measured to be n_tub ~2.90 and the high frequency tubulin dielectric constant kappa_tub ~8.41 while the high-frequency polarizability was found to be alpha_tub ~ 2.1x10^-33 C m^2/V. Methods for the experimental determination of the low-frequency p are explored as well as ways to test the often conjectured quantum coherence and entanglement properties of tubulin. Biobits, bioqubits and other applications to bioelectronics are discussed.

physics.bio-ph↗

arXiv2002

F-enomenology

The advantages of Flipped SU(5) over conventional Supersymmetric GUTs, like SU(5), are discussed. Recent values of the strong coupling at M_Z, sin-squared theta-Weinberg, g-2 of the muon, and the lower limit on the proton lifetime for the (K+, anti-neutrino) mode point directly to Flipped SU(5) as the simplest way to avoid potential pitfalls. It is shown that "F(lipped)-enomenology" accomodates easily all presently available low-energy data, favoring a rather "light" supersymmetric spectrum while yielding the right amount of Cold Dark Matter and a proton lifetime in the ((e+/muon+), pi-zero) mode which is beyond the present experimental limit yet still possibly accessible to a further round of experiments.

hep-ph↗

arXiv1998

Natural Candidates for Superheavy Dark Matter in String and M Theory

We reconsider superheavy dark matter candidates in string and M theory, in view of the possibility that inflation might generate superheavy particles with an abundance close to that required for a near-critical Universe. We argue that cryptons - stable or metastable bound states of matter in the hidden sector - are favoured over other possible candidates in string or $M$ theory, such as the Kaluza-Klein states associated with extra dimensions. We exhibit a specific string model that predicts cryptons as hidden-sector bound states weighing $\sim 10^{12}$ GeV, and discuss their astrophysical observability.

hep-ph↗