The Z2×Z2Z_2\times Z_2 Orbifold and the SUSY Flavor Problem

The characteristic property of the $Z_2\times Z_2$ orbifold is its cyclic permutation symmetry. It is argued that this property may be instrumental in explaining simultaneously the fermion mass hierarchy and the squark mass degeneracy. Detailed studies in free fermionic models that preserve the cyclic permutation symmetry of anomalous U(1) charges of the three generations are discussed.Comment: 9 pages. Standard Late

Phenomenological aspects of M-theory

The Standard Model data suggests the realization of grand unification structures in nature, in particular that of SO(10). A class of string vacua that preserve the SO(10) embedding, are the three generation free fermion heterotic-string models, that are related to Z2xZ2 orbifold compactification. Attempts to use the M-theory framework to explore further this class of models are discussed. Wilson line breaking of the SO(10) GUT symmetry results in super-heavy meta-stable states, which produce several exotic dark matter and UHECR candidates, with differing phenomenological characteristics. Attempts to develop the tools to study the properties of these states in forthcoming UHECR experiments are discussed. It is proposed that quantum mechanics arises from an equivalence postulate, that may lay the foundations for the rigorous formulation of quantum gravity.Comment: 25 pages. 6 figures. Standard Latex & iopart.cls. To appear in the proceedings of Beyond the Desert 02 - Accelerator and non Accelerator Approaches, Oulu, Finland, 2-7 June 200

Cosmological and phenomenological implications of Wilsonian matter in realistic superstring derived models

Superstring phenomenology aims at achieving two goals. The first is to reproduce the observed physics of the Standard Model. The second is to identify experimental signatures of superstring unification which, if observed, will provide further evidence for the validity of superstring theory. I discuss such potential signatures of superstring unification. I propose that proton lifetime constraints imply that the Standard Model gauge group must be obtained directly at the string level. In this case the unifying gauge group, for example $SO(10)$, is broken to the Standard Model gauge group by ``Wilson lines''. The symmetry breaking by ``Wilson line'' has important implications. It gives rise to exotic massless states which cannot fit into multiplets of the original unifying gauge group. This is an important feature because it results in conservation laws which forbid the interaction of the exotic ``Wilsonian'' states with the Standard Model states. The ``Wilsonian'' matter states then have important phenomenological implications. I discuss two such implications: exotic ``Wilsonian'' states as dark matter candidates and ``Wilsonian'' matter as the messenger sector in gauge mediated dynamical SUSY breaking scenarios.Comment: 22 pages. Standard Latex. 4 figures. epsf.te

On the origin of three generation free fermionic superstring models

The three generation superstring models in the free fermionic models have had remarkable success in describing the real--world. The most explored models use the NAHE set to obtain three generations and to separate the hidden and observable sectors. It is of course well known that the full NAHE set is not required in order to construct three generation free fermionic models. I argue that all the semi--realistic free fermionic models that have been constructed to date correspond to $Z_2\times Z_2$ orbifolds. Thus, the successes of the semi--realistic free fermionic models, if taken seriously, suggest that the true string vacuum is a $Z_2\times Z_2$ orbifold with nontrivial background fields and quantized Wilson lines.Comment: 12 pages, phyzzx.tex, tables.te

Deriving The Standard Model From Superstring Theory

I outline a program to derive the Standard Model directly from superstring theory. I present a class of three generation superstring standard--like models in the free fermionic formulation. I discuss some phenomenological properties of these models. In particular these models suggest an explanation for the top quark mass hierarchy. A numerical estimate yielded $m_t\sim175-180~GeV$. The general texture of fermion mass matrices was obtained from analysis of nonrenormalizable terms up to order $N=8$.I argue that the realistic features of these models are due to the underlying $Z_2\times Z_2$ orbifold, with standard embedding, at the free fermionic point in toroidal compactification space.Comment: IASSNS--HEP--94/21, 11 page

The Equivalence Postulate of Quantum Mechanics, Dark Energy and The Intrinsic Curvature of Elementary Particles

The equivalence postulate of quantum mechanics offers an axiomatic approach to quantum field theories and quantum gravity. The equivalence hypothesis can be viewed as adaptation of the classical Hamilton-Jacobi formalism to quantum mechanics. The construction reveals two key identities that underly the formalism in Euclidean or Minkowski spaces. The first is a cocycle condition, which is invariant under $D$--dimensional Mobius transformations with Euclidean or Minkowski metrics. The second is a quadratic identity which is a representation of the D-dimensional quantum Hamilton--Jacobi equation. In this approach, the solutions of the associated Schrodinger equation are used to solve the nonlinear quantum Hamilton-Jacobi equation. A basic property of the construction is that the two solutions of the corresponding Schrodinger equation must be retained. The quantum potential, which arises in the formalism, can be interpreted as a curvature term. I propose that the quantum potential, which is always non-trivial and is an intrinsic energy term characterising a particle, can be interpreted as dark energy. Numerical estimates of its magnitude show that it is extremely suppressed. In the multi--particle case the quantum potential, as well as the mass, are cumulative.Comment: 19 pages. Standard LaTe

Phenomenological survey of free fermionic heterotic-string models

A glossary overview of the phenomenological studies of quasi-realistic free fermionic heterotic string models is presented. I elaborate on the correspondence of these models with Z2XZ2 orbifolds.Comment: 14 pages. Standard LaTe

Superstring Phenomenology - A Personal Perspective

In the first part of this paper I review the construction of the realistic free fermionic models, as well as current attempts to study aspects of these models in the nonperturbative framework of M- and F-theories. I discuss the recent demonstration of a Minimal Superstring Standard Model, which contains in the observable sector, below the string scale, solely the MSSM charged spectrum, and provides further support to the assertion that the true string vacuum is connected to the Z_2 X Z_2 orbifold in the vicinity of the free fermionic point in the Narain moduli space. In the second part I review the recent formulation of quantum mechanics from an equivalence postulate, which offers a new perspective on the synthesis of gravity and quantum mechanics, and contemplate possible relations with string theory and beyond.Comment: 25 pages. Standard Latex & iopconf1.sty. To appear in the proceedings of Beyond the Desert 99 - Accelerator and non Accelerator Approaches, Castle Ringberg, Tegernsee, Germany, 6-12 June 199