TY  - INPR
A1  - Pfäffle, Frank
A1  - Stephan, Christoph A.
T1  - The Holst action by the spectral action principle
N2  - We investigate the Holst action for closed Riemannian 4-manifolds with orthogonal connections. For connections whose torsion has zero Cartan type component we show that the Holst action can be recovered from the heat asymptotics for the natural Dirac operator acting on left-handed spinor fields.
T3  - Preprints des Instituts für Mathematik der Universität Potsdam - 1(2012)19 
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-60032
ER  - 
TY  - INPR
A1  - Pfäffle, Frank
A1  - Stephan, Christoph A.
T1  - Chiral asymmetry and the spectral action
N2  - We consider orthogonal connections with arbitrary torsion on compact Riemannian manifolds. For the induced Dirac operators, twisted Dirac operators and Dirac operators of Chamseddine-Connes type we compute the spectral action. In addition to the Einstein-Hilbert action and the bosonic part of the Standard Model Lagrangian we find the Holst term from Loop Quantum Gravity, a coupling of the Holst term to the scalar curvature and a prediction for the value of the Barbero-Immirzi parameter.
T3  - Preprints des Instituts für Mathematik der Universität Potsdam - 1(2012)20 
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-60046
ER  - 
TY  - JOUR
A1  - Pfäffle, Frank
A1  - Stephan, Christoph A.
T1  - Chiral asymmetry and the spectral action
JF  - Communications in mathematical physics
N2  - We consider orthogonal connections with arbitrary torsion on compact Riemannian manifolds. For the induced Dirac operators, twisted Dirac operators and Dirac operators of Chamseddine-Connes type we compute the spectral action. In addition to the Einstein-Hilbert action and the bosonic part of the Standard Model Lagrangian we find the Holst term from Loop Quantum Gravity, a coupling of the Holst term to the scalar curvature and a prediction for the value of the Barbero-Immirzi parameter.
Y1  - 2013
U6  - https://doi.org/10.1007/s00220-012-1641-6
SN  - 0010-3616
SN  - 1432-0916
VL  - 321
IS  - 2
SP  - 283
EP  - 310
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Stephan, Christoph A.
T1  - A dark sector extension of the almost-commutative standard model
JF  - International journal of modern physics : A, Particles and fields, gravitation, cosmology, nuclear physics
N2  - We consider an extension of the Standard Model within the framework of Noncommutative Geometry. The model is based on an older model [C. A. Stephan, Phys. Rev. D 79, 065013 (2009)] which extends the Standard Model by new fermions, a new U(1)-gauge group and, crucially, a new scalar field which couples to the Higgs field. This new scalar field allows to lower the mass of the Higgs mass from similar to 170 GeV, as predicted by the Spectral Action for the Standard Model, to a value of 120-130 GeV. The shortcoming of the previous model lay in its inability to meet all the constraints on the gauge couplings implied by the Spectral Action. These shortcomings are cured in the present model which also features a "dark sector" containing fermions and scalar particles.
KW  - Noncommutative geometry
KW  - spectral triple
KW  - beyond Standard Model
KW  - Higgs boson
KW  - scalar fields
Y1  - 2014
U6  - https://doi.org/10.1142/S0217751X14500055
SN  - 0217-751X
SN  - 1793-656X
VL  - 29
IS  - 1
PB  - World Scientific
CY  - Singapore
ER  -