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Alon E. Faraggi

Publications and source records attributed to Alon E. Faraggi.

At least 73 records · Page 4Linked to original sources
arXiv2011

Top Quark Mass in Exophobic Pati--Salam Heterotic String Model

We analyse the phenomenology of an exemplary exophobic Pati-Salam heterotic string vacuum, in which no exotic fractionally charged states exist in the massless string spectrum. Our model also contains the Higgs representations that are needed to break the gauge symmetry to that of the Standard Model and to generate fermion masses at the electroweak scale. We show that the requirement of a leading mass term for the heavy generation, which is not degenerate with the mass terms of the lighter generations, places an additional strong constraint on the viability of the models. In many models a top quark Yukawa may not exist at all, whereas in others two or more generations may obtain a mass term at leading order. In our exemplary model a mass term at leading order exist only for one family. Additionally, we demonstrate the existence of supersymmetric F- and D-flat directions that give heavy mass to all the colour triplets beyond those of the Standard Model and leave one pair of electroweak Higgs doublets light. Hence, below the Pati-Salam breaking scale, the matter states in our model that are charged under the observable gauge symmetries, consist solely of those of the Minimal Supersymmetric Standard Model.

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arXiv2011

Classification of Heterotic Pati-Salam Models

We extend the classification of free fermionic heterotic-string models to vacua in which the SO(10) GUT symmetry is broken at the string level to the Pati-Salam subgroup. Using our classification method we recently presented the first example of a quasi--realistic heterotic-string vacuum that is free of massless exotic states. Within this method we are able to derive algebraic expressions for the generalised GSO projections for all sectors that appear in the models. This facilitates the programming of the entire spectrum analysis in a computer code. The total number of vacua in the class of models that we classify is 2^{51} ~ 10^{15}. We perform a statistical sampling in this space of models and extract 10^{11} distinct configurations with Pati-Salam gauge group. Our results demonstrate that one in every 10^{6} vacua correspond to a three generation exophobic model with the required Higgs states, needed to induce spontaneous breaking to the Standard Model.

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arXiv2011

Conformal Aspects of Spinor-Vector Duality

We present a detailed study of various aspects of Spinor-Vector duality in Heterotic string compactifications and expose its origin in terms of the internal conformal field theory. In particular, we illustrate the main features of the duality map by using simple toroidal orbifolds preserving N_4 = 1 and N_4 = 2 spacetime supersymmetries in four dimensions. We explain how the duality map arises in this context by turning on special values of the Wilson lines around the compact cycles of the manifold. We argue that in models with N_4 = 2 spacetime supersymmetry, the interpolation between the Spinor-Vector dual vacua can be continuously realized. We trace the origin of the Spinor-Vector duality map to the presence of underlying N = (2, 2) and N = (4, 4) SCFTs, and explicitly show that the induced spectral-flow in the twisted sectors is responsible for the observed duality. The isomorphism between current algebra representations gives rise to a number of chiral character identities, reminiscent of the recently-discovered MSDS symmetry.

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arXiv2011

On the Equivalence of String Vacua

The heterotic-string models in the free fermionic formulation are among the most realistic string vacua constructed to date, which motivates their detailed exploration. Classification of free fermionic heterotic-string vacua revealed a duality under exchange of spinor and vector representations of the SO(10) GUT symmetry. The spinor-vector duality was subsequently demonstrated in a Z2 X Z2 X Z2 orbifold, in which the map is realised as exchange of discrete torsions. Analysis of the orbifold partition function shows that the duality map preserves the number of massless twisted states. While the dual vacua are distinct from the point of view of the low energy field theory it is suggested that they are equivalent from the string point of view and may be connected by continuous and discrete transformations.

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arXiv2010

MSHSM - Minimal Standard Heterotic String Models

An overview of old and new results in studies of the quasi-realistic free fermionic models is presented, which include the recent discovery of exophobic string vacua and reproduction of the Higgs-matter splitting mechanism in a corresponding orbifold construction.

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arXiv2009

Interpolations Among NAHE-based Supersymmetric and Nonsupersymmetric String Vacua

The quasi-realistic free fermionic heterotic-string models provide some of the most detailed examples to explore the phenomenology of string unification. While providing a powerful tool to generate models and their spectra, understanding the realisation of the free fermion models in a bosonic formalism will provide important insight into their basic properties away from the free fermion point. In this paper we elucidate bosonic equivalent of the basic symmetry breaking pattern in the free fermion models from E8XE8 to SO(16)XSO(16) and exhibit the connection of the free fermion models with corresponding non--supersymmetric vacua by interpolations.

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arXiv2009

The Equivalence Postulate of Quantum Mechanics: Main Theorems

We consider the two main theorems in the derivation of the Quantum Hamilton--Jacobi Equation from the Equivalence Postulate (EP) of quantum mechanics. The first one concerns a basic cocycle condition, which holds in any dimension with Euclidean or Minkowski metrics and implies a global conformal symmetry underlying the Quantum Hamilton--Jacobi Equation. In one dimension such a condition fixes the Schwarzian equation. The second theorem concerns energy quantization which follows rigorously from consistency of the equivalence postulate.

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arXiv2009

Exophobic Quasi-Realistic Heterotic String Vacua

We demonstrate the existence of heterotic-string vacua that are free of massless exotic fields. The need to break the non-Abelian GUT symmetries in k=1 heterotic-string models by Wilson lines, while preserving the GUT embedding of the weak-hypercharge and the GUT prediction sin^2θ_w(M(GUT))=3/8, necessarily implies that the models contain states with fractional electric charge. Such states are severely restricted by observations, and must be confined or sufficiently massive and diluted. We construct the first quasi-realistic heterotic-string models in which the exotic states do not appear in the massless spectrum, and only exist, as they must, in the massive spectrum. The SO(10) GUT symmetry is broken to the Pati-Salam subgroup. Our PS heterotic-string models contain adequate Higgs representations to break the GUT and electroweak symmetry, as well as colour Higgs triplets that can be used for the missing partner mechanism. By statistically sampling the space of Pati-Salam vacua we demonstrate the abundance of quasi--realistic three generation models that are completely free of massless exotics, rendering it plausible that obtaining realistic Yukawa couplings may be possible in this space of models.

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arXiv2009

Little heterotic strings

We discuss toroidal orbifolds of the E8XE8 heterotic string, in which the free fermionic Higgs-matter splitting is implemented by a shift in the internal lattice coupled with the fermion numbers of the gauge degrees of freedom. We consider models in which some choices of the orbifold result in the projection of the graviton. In the models that we consider the projection also results in flipping the spin-statistics assignments in the massive string spectrum, whereas the massless spectrum retains the conventional spin-statistics assignments. We argue that the partition functions are mathematically consistent for one- and multi-loop amplitudes, owning to the existence of supersymmetry in the spectrum. A duality between different models at nonzero temperature is briefly discussed.

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arXiv2009

Proceedings of the Workshop on Monte Carlo's, Physics and Simulations at the LHC PART II

These proceedings collect the presentations given at the first three meetings of the INFN "Workshop on Monte Carlo's, Physics and Simulations at the LHC", held at the Frascati National Laboratories in 2006. The first part of these proceedings contains pedagogical introductions to several basic topics of both theoretical and experimental high pT LHC physics. The second part collects more specialised presentations.

hep-ph↗
arXiv2009

Proceedings of the Workshop on Monte Carlo's, Physics and Simulations at the LHC PART I

These proceedings collect the presentations given at the first three meetings of the INFN "Workshop on Monte Carlo's, Physics and Simulations at the LHC", held at the Frascati National Laboratories in 2006. The first part of these proceedings contains pedagogical introductions to several basic topics of both theoretical and experimental high pT LHC physics. The second part collects more specialised presentations.

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arXiv2008

Quasi-realistic heterotic-string models with vanishing one-loop cosmological constant and perturbatively broken supersymmetry?

Quasi-realistic string models in the free fermionic formulation typically contain an anomalous U(1), which gives rise to a Fayet-Iliopoulos D-term that breaks supersymmetry at the one--loop level in string perturbation theory. Supersymmetry is traditionally restored by imposing F- and D-flatness on the vacuum. By employing the standard analysis of flat directions we present a quasi--realistic three generation string model in which stringent F- and D-flat solution do not appear to exist to all orders in the superpotential. We speculate that this result is indicative of the non-existence of supersymmetric flat F- and D-solutions in this model. We provide some arguments in support of this scenario and discuss its potential implications. Bose-Fermi degeneracy of the string spectrum implies that the one--loop partition function and hence the one-loop cosmological constant vanishes in the model. If our assertion is correct, this model may represent the first known example with vanishing cosmological constant and perturbatively broken supersymmetry. We discuss the distinctive properties of the internal free fermion boundary conditions that may correspond to a large set of models that share these properties. The geometrical moduli in this class of models are fixed due to asymmetric boundary conditions, whereas absence of supersymmetric flat directions would imply that the supersymmetric moduli are fixed as well and the dilaton may be fixed by hidden sector nonperturbative effects.

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arXiv2008

Spinor-Vector Duality in Heterotic SUSY Vacua

We elaborate on the recently discovered spinor-vector duality in realistic free fermionic heterotic vacua. We emphasize the interpretation of the freely-acting orbifolds carried out on the six internal dimensions as coordinate-dependent compactifications; they play a central role in the duality, especially because of their ability to break the right-moving superconformal algebra of the space-time supersymmetric heterotic vacua. These considerations lead to a simple and intuitive proof of the spinor-vector duality, and to the formulation of explicit rules to find the dual of a given model. We discuss the interest of such a duality, notably concerning the structure of the space of vacua of superstring theory.

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arXiv2008

Z-prime Searches at the LHC: Some QCD Precision Studies in Drell-Yan

Discovery potentials for extra neutral interactions at the Large Hadron Collider in forthcoming experiments are analyzed in Drell-Yan. For this purpose we use high precision next-to-next-to-leading order (NNLO) determination of the mass invarian distributions and of the total cross sections in the kinematic region around 1 TeV. In this region we explore the possibility to make a preliminary distinction between different anomaly-free extentions of the Standard Model.

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arXiv2008

Searching for Extra Z' from Strings and Other Models at the LHC with Leptoproduction

Discovery potentials for extra neutral interactions at the Large Hadron Collider in forthcoming experiments are analyzed using resonant leptoproduction. For this purpose we use high precision next-to-next-to-leading order (NNLO) determinations of the QCD background in this channel, at the tail of the Drell-Yan distributions, in the invariant mass region around $ 0.8< Q < 2.5 $ TeV. We focus our analysis primarily on a novel string-inspired $Z^\prime$, obtained in left-right symmetric free fermionic heterotic string models and whose existence at low energies is motivated by its role in suppressing proton decay mediation. We analyze the parametric dependence of the predictions and perform comparison with other models based on bottom up approaches, that are constructed by requiring anomaly cancellation and enlarged Higgs structure. We show that the results are not particularly sensitive to the specific charge assignments. This may render quite difficult the extraction of significant information from the forward-backward asymmetries on the resonance, assuming that these are possible due to a sizeable width. The challenge to discover extra (non anomalous) $Z^\prime$ in this kinematic region remains strongly dependent on the size of the new gauge coupling. Weakly coupled extra $Z^\prime$ will not be easy to identify even with a very good theoretical determination of the QCD background through NNLO.

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arXiv2008

On the Low Energy Spectra of the Nonsupersymmetric Heterotic String Theories

The ten dimensional string theories as well as eleven dimensional supergravity are conjectured to arise as limits of a more basic theory, traditionaly dubbed M--theory. This notion is confined to the ten dimensional supersymmetric theories. String theory, however, also contains ten dimensional nonsupersymmetric theories that have not been incorporated into this picture. In this note we explore the possibility of generating the low energy spectra of various nonsupersymmetric heterotic string vacua form the Horava--Witten model. We argue that this can be achieved by imposing on the Horava--Witten model an invariance with respect to some extra operators which identify the orbifold fixed planes in a nontrivial way, and demonstrate it for the E_8 and SO(16)XSO(16) heterotic string vacua in ten dimensions.

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arXiv2007

Spinor-Vector Duality in N=2 Heterotic String Vacua

Classification of the N=1 space-time supersymmetric fermionic Z2XZ2 heterotic-string vacua with symmetric internal shifts, revealed a novel spinor-vector duality symmetry over the entire space of vacua, where the S_t <-> V duality interchanges the spinor plus anti-spinor representations with vector representations. In this paper we demonstrate that the spinor--vector duality exists also in fermionic Z2 heterotic string models, which preserve N=2 space-time supersymmetry. In this case the interchange is between spinorial and vectorial representations of the unbroken SO(12) GUT symmetry. We provide a general algebraic proof for the existence of the S_t <-> V duality map. We present a novel basis to generate the free fermionic models in which the ten dimensional gauge degrees of freedom are grouped into four groups of four, each generating an SO(8) modular block. In the new basis the GUT symmetries are produced by generators arising from the trivial and non--trivial sectors, and due to the triality property of the SO(8) representations. Thus, while in the new basis the appearance of GUT symmetries is more cumbersome, it may be more instrumental in revealing the duality symmetries that underly the string vacua.

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