452 research outputs found
M-Phenomenology
Recent developments involving strongly coupled superstrings are discussed
from a phenomenological point of view. In particular, strongly coupled
is described as an appropriate long-wavelength limit of
M-theory, and some generic phenomenological implications are analyzed,
including a long sought downward shift of the string unification scale and a
novel way to break supersymmetry. A specific scenario is presented that leads
to a rather light, and thus presently experimentally testable, sparticle
spectrum.Comment: 22 pages, 2 figure
The Electroweak Phase Transition in Minimal Supergravity Models
We have explored the electroweak phase transition in minimal supergravity
models by extending previous analysis of the one-loop Higgs potential to
include finite temperature effects. Minimal supergravity is characterized by
two higgs doublets at the electroweak scale, gauge coupling unification, and
universal soft-SUSY breaking at the unification scale. We have searched for the
allowed parameter space that avoids washout of baryon number via unsuppressed
anomalous Electroweak sphaleron processes after the phase transition. This
requirement imposes strong constraints on the Higgs sector. With respect to
weak scale baryogenesis, we find that the generic MSSM is {\it not}
phenomenologically acceptable, and show that the additional experimental and
consistency constraints of minimal supergravity restricts the mass of the
lightest CP-even Higgs even further to m_h\lsim 32\GeV (at one loop), also in
conflict with experiment. Thus, if supergravity is to allow for baryogenesis
via any other mechanism above the weak scale, it {\it must} also provide for
B-L production (or some other `accidentally' conserved quantity) above the
electroweak scale. Finally, we suggest that the no-scale flipped
supergravity model can naturally and economically provide a source of B-L
violation and realistically account for the observed ratio .Comment: 14 pages (not including two postscript figures available upon
request
A Non-critical String (Liouville) Approach to Brain Microtubules: State Vector reduction, Memory coding and Capacity
Microtubule (MT) networks, subneural paracrystalline cytosceletal structures,
seem to play a fundamental role in the neurons. We cast here the complicated MT
dynamics in the form of a -dimensional non-critical string theory, thus
enabling us to provide a consistent quantum treatment of MTs, including
enviromental {\em friction} effects. Quantum space-time effects, as described
by non-critical string theory, trigger then an {\em organized collapse} of the
coherent states down to a specific or {\em conscious state}. The whole process
we estimate to take . The {\em microscopic arrow of
time}, endemic in non-critical string theory, and apparent here in the
self-collapse process, provides a satisfactory and simple resolution to the
age-old problem of how the, central to our feelings of awareness, sensation of
the progression of time is generated. In addition, the complete integrability
of the stringy model for MT we advocate in this work proves sufficient in
providing a satisfactory solution to memory coding and capacity. Such features
might turn out to be important for a model of the brain as a quantum computer.Comment: 70 pages Latex, 4 figures (not included), minor corrections, no
effect on conclusion
On a possible connection of non-critical strings to certain aspects of quantum brain function
We review certain aspects of brain function which could be associated with
non-critical (Liouville) string theory. In particular we simulate the physics
of brain microtubules (MT) by using a (completely integrable) non-critical
string, we discuss the collapse of the wave function as a result of quantum
gravity effects due to abrupt conformational changes of the MT protein dimers,
and we propose a new mechanism for memory coding.Comment: Invited talk by D.V. Nanopoulos at the `four-seas conference',
Trieste (Italy), 25 June-1 July 1995; latex file, 9 pages, one macro:
4seas95.sty, available from archive
Flipped Cryptons and the UHECRs
Cryptons are metastable bound states of fractionally-charged particles that
arise generically in the hidden sectors of models derived from heterotic
string. We study their properties and decay modes in a specific flipped SU(5)
model with long-lived four-particle spin-zero bound states called {\it
tetrons}. We show that the neutral tetrons are metastable, and exhibit the
tenth-order non-renormalizable superpotential operators responsible for their
dominant decays. By analogy with QCD, we expect charged tetrons to be somewhat
heavier, and to decay relatively rapidly via lower-order interactions that we
also exhibit. The expected masses and lifetimes of the neutral tetrons make
them good candidates for cold dark matter (CDM), and a potential source of the
ultra-high energy cosmic rays (UHECRs) which have been observed, whereas the
charged tetrons would have decayed in the early Universe.Comment: 8 Pages RevTex. New version with expanded introduction to flipped
SU(5). Accepted for publication in PR
Moduli and K\"ahler potential in fermionic strings
We study the problem of identifying the moduli fields in fermionic
four-dimensional string models. We deform a free-fermionic model by introducing
exactly marginal operators in the form of Abelian Thirring interactions on the
world-sheet, and show that their couplings correspond to the untwisted moduli
fields. We study the consequences of this method for simple free-fermionic
models which correspond to orbifolds and obtain their moduli
space and K\"ahler potential by symmetry arguments and by direct calculation of
string scattering amplitudes. We then generalize our analysis to more
complicated fermionic structures which arise in constructions of realistic
models corresponding to asymmetric orbifolds, and obtain the moduli space and
K\"ahler potential for this case. Finally we extend our analysis to the
untwisted matter sector and derive expressions for the full K\"ahler potential
to be used in phenomenological applications, and the target space duality
transformations of the corresponding untwisted matter fields.Comment: 27pp Latex text, no figs, CERN-TH.7259/94, CTP-TAMU-14/94 and
ACT-06/9
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