scholarly journals GAUGE SYMMETRY BREAKING IN ORBIFOLD MODEL BUILDING

2006 ◽  
Vol 21 (30) ◽  
pp. 2251-2267 ◽  
Author(s):  
MICHELE TRAPLETTI
Keyword(s):  
Gauge Symmetry ◽  
Symmetry Breaking ◽  
Extra Dimensions ◽  
Model Building ◽  
String Model ◽  
Open String ◽  
Internal Space ◽  
Four Dimensions ◽  
String Compactifications ◽  
Breaking Mechanism

We review the gauge symmetry breaking mechanism due to orbifold projections in orbifold model building. We explicitly show the existence of a scale of breaking if such a symmetry breaking is due to freely-acting orbifold operators only, i.e. in case the breaking is realized nonlocally in the internal space. We show that such a scale is related to the compactification moduli only, and that there are no extra continuous parameters, at least in semirealistic models with [Formula: see text] SUSY in four dimensions. In this sense, the mechanism is peculiarly different from the standard Higgs (or Hosotani) symmetry breaking mechanism. We show that the mechanism also differs from that present in standard orbifold models where, even in the presence of discrete Wilson lines, a scale of breaking is generically missing, since the breaking is localized in specific points in the internal space. We review a set of background geometries where the described nonlocal breaking is realized, both in the case of two and six extra dimensions. In the latter case, relevant in string model building, we consider both heterotic and open string compactifications.

ON TIME VARIATION OF FUNDAMENTAL CONSTANTS IN SUPERSTRING THEORIES

1988 ◽  
Vol 03 (03) ◽  
pp. 243-249 ◽  
Author(s):  
KEI-ICHI MAEDA
Keyword(s):  
String Theory ◽  
Symmetry Breaking ◽  
Time Variation ◽  
Susy Breaking ◽  
Internal Space ◽  
Fundamental Constants ◽  
Breaking Mechanism ◽  
Dimensional Gravity ◽  
Superstring Theories ◽  
String Theories

Assuming the action from the string theory and taking into account the dynamical freedom of a dilaton and its coupling to matter fluid, we show that fundamental ‘constants’ in string theories are independent of the ‘radius’ of the internal space. Since the scalar related to the ‘constants’ is coupled to the 4-dimensional gravity and matter fluid in the same way as in the Jordan-Brans-Dicke theory with ω=−1, it must be massive and can get a mass easily through some symmetry breaking mechanism (e.g. the SUSY breaking due to a gluino condensation). Consequently, time variation of fundamental constants is too small to be observed.

GAUGE SYMMETRY BREAKING IN SUPERCONFORMAL ORBIFOLDS

1991 ◽  
Vol 06 (07) ◽  
pp. 591-603
Author(s):  
B.R. GREENE ◽  
M.R. PLESSER ◽  
EDMOND RUSJAN ◽  
XING-MIN WANG
Keyword(s):  
Gauge Symmetry ◽  
Symmetry Breaking ◽  
Symmetry Group ◽  
Free Group ◽  
Group Actions ◽  
Wilson Loops ◽  
String Compactifications ◽  
Free Group Actions

We study the construction of (2, 0) theories from orbifolds of N=2 minimal superconformal string compactifications with non-trivial Wilson loops. In particular, we exploit the connection between geometrical and exactly soluble string vacua to arrive at a mean of analyzing Calabi-Yau orbifolds containing ‘Wilson loops’ associated with non-free group actions, breaking the E6 gauge symmetry of the model as well the ‘shadow’ E8 gauge symmetry group. We apply our results to recently proposed three generation constructions of this sort and find spectra which differ from previous claims and which possess exceptionally desirable phenomenological properties.

scholarly journals From Type II string theory toward BSM/dark sector physics

2016 ◽  
Vol 31 (34) ◽  
pp. 1630050 ◽  
Author(s):  
Gabriele Honecker
Keyword(s):  
String Theory ◽  
Open String ◽  
New Physics ◽  
Closed String ◽  
Type Ii ◽  
Dark Sector ◽  
Four Dimensions ◽  
Brane Model ◽  
Moduli Stabilization ◽  
String Compactifications

Four-dimensional compactifications of string theory provide a controlled set of possible gauge representations accounting for BSM particles and dark sector components. In this review, constraints from perturbative Type II string compactifications in the geometric regime are discussed in detail and then compared to results from heterotic string compactifications and nonperturbative/nongeometric corners. As a prominent example, an open string realization of the QCD axion is presented. The status of deriving the associated low-energy effective action in four dimensions is discussed and open avenues of major phenomenological importance are highlighted. As examples, a mechanism of closed string moduli stabilization by D-brane backreaction as well as one-loop threshold corrections to the gauge couplings and balancing a low string scale [Formula: see text] with unisotropic compact dimensions are discussed together with implications on potential future new physics observations. For illustrative purposes, an explicit example of a globally consistent D6-brane model with MSSM-like spectrum on [Formula: see text] is presented.

FLIPPED SU(6) FROM TEN DIMENSIONS

1990 ◽  
Vol 05 (12) ◽  
pp. 2359-2390 ◽  
Author(s):  
C. PANAGIOTAKOPOULOS
Keyword(s):  
Discrete Symmetries ◽  
Model Building ◽  
Realistic Model ◽  
Low Energy ◽  
Internal Space ◽  
Fast Proton ◽  
Hierarchy Problem ◽  
Four Dimensions ◽  
Gauge Hierarchy ◽  
Breaking Scale

We study the compactification of the heterotic superstring on the only known three generation Calabi-Yau space with flux breakings leading to SU (6) × U (1) as the gauge group in four dimensions. We compute the 'massless' spectrum and identify the discrete symmetries of the internal space that survive flux breaking. The possible four-dimensional models are classified according to their honest discrete symmetries. The allowed breaking chains of SU (6) × U (1) are listed. Model building with SU (6) × U (1) is discussed in general and a concrete realistic model is constructed which does not suffer from the gauge hierarchy problem, fast proton decay or any other obvious phenomenological disaster. A distinct experimental signature of this class of models is the presence in the low energy spectrum of vector-like quarks and antiquarks, outside the three known families, with masses of the order of the supersymmetry breaking scale.

Open string model building

1989 ◽  
Vol 318 (1) ◽  
pp. 239-280 ◽  
Author(s):  
Nobuyuki Ishibashi ◽  
Tetsuya Onogi
Keyword(s):  
Model Building ◽  
String Model ◽  
Open String

Physics of superheavy dark matter in supergravity

2018 ◽  
Vol 27 (06) ◽  
pp. 1841011 ◽  
Author(s):  
Andrea Addazi ◽  
Antonino Marciano ◽  
Sergei V. Ketov ◽  
Maxim Yu. Khlopov
Keyword(s):  
Dark Matter ◽  
Gauge Symmetry ◽  
Particle Physics ◽  
Cold Dark Matter ◽  
Model Building ◽  
Density Fluctuations ◽  
String Compactifications ◽  
Matter Production ◽  
The Right ◽  
Superheavy Dark Matter

New trends in inflationary model building and dark matter production in supergravity are considered. Starobinsky inflation is embedded into [Formula: see text] supergravity, avoiding instability problems, when the inflaton belongs to a vector superfield associated with a [Formula: see text] gauge symmetry, instead of a chiral superfield. This gauge symmetry can be spontaneously broken by the super-Higgs mechanism resulting in a massive vector supermultiplet including the (real scalar) inflaton field. Both supersymmetry (SUSY) and the R-symmetry can also be spontaneously broken by the Polonyi mechanism at high scales close to the inflationary scale. In this case, Polonyi particles and gravitinos become superheavy, and can be copiously produced during inflation by the Schwinger mechanism sourced by the universe expansion. The Polonyi mass slightly exceeds twice the gravitino mass, so that Polonyi particles are unstable and decay into gravitinos. Considering the mechanisms of superheavy gravitino production, we find that the right amount of cold dark matter composed of gravitinos can be achieved. In our scenario, the parameter space of the inflaton potential is directly related to the dark matter one, providing a new unifying framework of inflation and dark matter genesis. A multi-superfield extension of the supergravity framework with a single (inflaton) superfield can result in a formation of primordial nonlinear structures like mini- and stellar-mass black holes, primordial nongaussianity, and the running spectral index of density fluctuations. This framework can be embedded into the SUSY GUTs inspired by heterotic string compactifications on Calabi–Yau three-folds, thus unifying particle physics with quantum gravity.

scholarly journals OBSERVABLE/HIDDEN SECTOR BROKEN SYMMETRY FOR SYMMETRIC BOUNDARY CONDITIONS

2006 ◽  
Vol 21 (16) ◽  
pp. 3367-3385 ◽  
Author(s):  
B. DUNDEE ◽  
J. PERKINS ◽  
G. CLEAVER
Keyword(s):  
Gauge Symmetry ◽  
Symmetry Breaking ◽  
Boundary Conditions ◽  
Mirror Symmetry ◽  
String Model ◽  
Broken Symmetry ◽  
Chiral Model ◽  
Universe Model ◽  
Gauge Groups ◽  
Hidden Sector

A four-dimensional heterotic string model of free fermionic construction is presented wherein mirror symmetry breaking between observable and hidden sector gauge groups occurs in spite of mirror symmetry between observable and hidden sector worldsheet fermion boundary conditions. The differentiation is invoked by an asymmetry in GSO projections necessarily resulting from the symmetry of the free fermionic boundary conditions. In the specific examples shown, an expected nonchiral Pati–Salam mirror universe model is transformed into a chiral model with enhanced hidden sector gauge symmetry and reduced observable sector gauge symmetry: [ SU (4)C ⊗ SU (2)L ⊗ SU (2)R]O ⊗ [ SU (4)C ⊗ SU (2)L ⊗ SU (2)R]H, is necessarily transformed into a chiral [ SU (4)C ⊗ SU (2)L]O ⊗ [ SO (10) ⊗ SU (2)R]H model because of an unavoidable asymmetry in GSO projections.

scholarly journals Many-body Majorana-like zero modes without gauge symmetry breaking

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
V. Vadimov ◽  
T. Hyart ◽  
J. L. Lado ◽  
M. Möttönen ◽  
T. Ala-Nissila
Keyword(s):  
Gauge Symmetry ◽  
Symmetry Breaking ◽  
Many Body ◽  
Zero Modes

scholarly journals Kinetic mixing, dark photons and extra dimensions. Part III. Brane localized dark matter

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Thomas G. Rizzo ◽  
George N. Wojcik
Keyword(s):  
Dark Matter ◽  
Extra Dimensions ◽  
Model Building ◽  
New Physics ◽  
Model Complexity ◽  
Complex Scalar ◽  
Dark Photon ◽  
Complex Models ◽  
The Cost ◽  
D Model

Abstract Extra dimensions have proven to be a very useful tool in constructing new physics models. In earlier work, we began investigating toy models for the 5-D analog of the kinetic mixing/vector portal scenario where the interactions of dark matter, taken to be, e.g., a complex scalar, with the brane-localized fields of the Standard Model (SM) are mediated by a massive U(1)D dark photon living in the bulk. These models were shown to have many novel features differentiating them from their 4-D analogs and which, in several cases, avoided some well-known 4-D model building constraints. However, these gains were obtained at the cost of the introduction of a fair amount of model complexity, e.g., dark matter Kaluza-Klein excitations. In the present paper, we consider an alternative setup wherein the dark matter and the dark Higgs, responsible for U(1)D breaking, are both localized to the ‘dark’ brane at the opposite end of the 5-D interval from where the SM fields are located with only the dark photon now being a 5-D field. The phenomenology of such a setup is explored for both flat and warped extra dimensions and compared to the previous more complex models.

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