Loop-and-allied QG bibliography

[marcus]

http://arxiv.org/abs/1209.3403
Quantum Cosmology: Effective Theory
Martin Bojowald
(Submitted on 15 Sep 2012)
Quantum cosmology has traditionally been studied at the level of symmetry-reduced minisuperspace models, analyzing the behavior of wave functions. However, in the absence of a complete full setting of quantum gravity and detailed knowledge of specific properties of quantum states, it remained difficult to make testable predictions. For quantum cosmology to be part of empirical science, it must allow for a systematic framework in which corrections to well-tested classical equations can be derived, with any ambiguities and ignorance sufficiently parameterized. As in particle and condensed-matter physics, a successful viewpoint is one of effective theories, adapted to specific issues one encounters in quantum cosmology. This review presents such an effective framework of quantum cosmology, taking into account, among other things, space-time structures, covariance, the problem of time and the anomaly issue.
75 pages, 3 figures, Invited Topical Review for Class. Quantum Grav. 29 (2012) 213001

http://arxiv.org/abs/1209.3623
An Approach to Loop Quantum Cosmology Through Integrable Discrete Heisenberg Spin Chains
Christine C. Dantas
(Submitted on 17 Sep 2012)
The quantum evolution equation of Loop Quantum Cosmology (LQC) -- the quantum Hamiltonian constraint -- is a difference equation. We relate the LQC constraint equation in vacuum Bianchi I separable (locally rotationally symmetric) models with an integrable differential-difference nonlinear Schrödinger type equation, which in turn is known to be associated with integrable, discrete Heisenberg spin chain models in condensed matter physics. We illustrate the similarity between both systems with a simple constraint in the linear regime.
6 pages, submitted to Foundations of Physics

http://arxiv.org/abs/1209.3649
Functional renormalization with fermions and tetrads
Pietro Donà, Roberto Percacci
(Submitted on 17 Sep 2012)
We investigate some aspects of the renormalization group flow of gravity in the presence of fermions, which have remained somewhat puzzling so far. The first is the sign of the fermionic contribution to the running of Newton's constant, which depends on details of the cutoff. We argue that only one of the previously used schemes correctly implements the cutoff on eigenvalues of the Dirac operator, and it acts in the sense of screening Newton's constant. We also show that Kähler fermions give the same contribution to the running of the cosmological and Newton constant as four Dirac spinors. We then calculate the graviton contributions to the beta functions by imposing the cutoffs on the irreducible spin components of the tetrad. In this way we can probe the gauge dependence of the off-shell flow. The results resemble closely those of the metric formalism, except for an increased scheme-- and (off shell) gauge--dependence.
28 pages, 4 figures

brief mention:
http://arxiv.org/abs/1209.3511
The effective field theory treatment of quantum gravity
John F. Donoghue
(Submitted on 16 Sep 2012)
This is a pedagogical introduction to the treatment of quantum general relativity as an effective field theory...
22 pages, 3 figures. Presented at the Sixth International School on Field Theory and Gravitation, Petropolis, Brazil, April 2012, to be published in the proceedings.

http://arxiv.org/abs/1209.3339
Annual Modulation of Dark Matter: A Review
Katherine Freese, Mariangela Lisanti, Christopher Savage
(Submitted on 14 Sep 2012)
Direct detection experiments, which are designed to detect the scattering of dark matter off nuclei in detectors, are a critical component in the search for the Universe's missing matter. The count rate in these experiments should experience an annual modulation due to the relative motion of the Earth around the Sun...
37 pages, 7 figures. To appear in Review of Modern Physics

 

[marcus]

http://arxiv.org/abs/1209.4038
Fixed points and infrared completion of quantum gravity
Nicolai Christiansen, Daniel F. Litim, Jan M. Pawlowski, Andreas Rodigast
(Submitted on 18 Sep 2012)
The phase diagram of four-dimensional Einstein-Hilbert gravity is studied using Wilson's renormalization group. Smooth trajectories connecting the ultraviolet fixed point at short distances with attractive infrared fixed points at long distances are derived from the non-perturbative graviton propagator. Implications for the asymptotic safety conjecture and further results are discussed.
4 pages, 4 figures

 

[marcus]

http://arxiv.org/abs/1209.4295
A review of the large N limit of tensor models
Razvan Gurau
(Submitted on 19 Sep 2012)
Random matrix models encode a theory of random two dimensional surfaces with applications to string theory, conformal field theory, statistical physics in random geometry and quantum gravity in two dimensions. The key to their success lies in the 1/N expansion introduced by 't Hooft. Random tensor models generalize random matrices to theories of random higher dimensional spaces. For a long time, no viable 1/N expansion for tensors was known and their success was limited.
A series of recent results has changed this situation and the extension of the 1/N expansion to tensors has been achieved. We review these results in this paper.
12 pages. Proceedings of The XXIX International Colloquium on Group-Theoretical Methods in Physics, August 20-26 2012, Chern Institute of Mathematics, Nankai University, Tianjin, China

 

[marcus]

http://arxiv.org/abs/1209.4374
On the Uniqueness of Kinematics of Loop Quantum Cosmology
Abhay Ashtekar, Miguel Campiglia
(Submitted on 19 Sep 2012)
The holonomy-flux algebra A of loop quantum gravity is known to admit a natural representation that is uniquely singled out by the requirement of covariance under spatial diffeomorphisms. In the cosmological context, the requirement of spatial homogeneity naturally reduces A to a much smaller algebra, A_Red, used in loop quantum cosmology. In Bianchi I models, it is shown that the requirement of covariance under residual diffeomorphism symmetries again uniquely selects the representation of A_Red that has been commonly used. We discuss the close parallel between the two uniqueness results and also point out a difference.
9 pages

http://arxiv.org/abs/1209.4539
Holonomy Spin Foam Models: Boundary Hilbert spaces and Time Evolution Operators
Bianca Dittrich, Frank Hellmann, Wojciech Kaminski
(Submitted on 20 Sep 2012)
In this and the companion paper a novel holonomy formulation of so called Spin Foam models of lattice gauge gravity are explored. After giving a natural basis for the space of simplicity constraints we define a universal boundary Hilbert space, on which the imposition of different forms of the simplicity constraints can be studied. We detail under which conditions this Hilbert space can be mapped to a Hilbert space of projected spin networks or an ordinary spin network space.
These considerations allow to derive the general form of the transfer operators which generates discrete time evolution. We will describe the transfer operators for some current models on the different boundary Hilbert spaces and highlight the role of the simplicity constraints determining the concrete form of the time evolution operators.
51 pages, 18 figures

http://arxiv.org/abs/1209.4376
Multi-fractional spacetimes, asymptotic safety and Hořava-Lifgarbagez gravity
Gianluca Calcagni
(Submitted on 19 Sep 2012)
We compare the recently formulated multi-fractional spacetimes with field theories of quantum gravity based on the renormalization group (RG), such as asymptotic safety and Horava-Lifgarbagez gravity. The change of spacetime dimensionality with the probed scale is realized in both cases by an adaptation of the measurement tools (`rods') to the scale, but in different ways. In the multi-fractional case, by an adaptation of the position-space measure, roughly corresponding to a scale dependence of the coordinates. In the case of RG-based theories, by an adaptation of the momenta. The two pictures are mapped into each other, thus presenting the fractal structure of spacetime in RG-based theories under an alternative perspective.
17 pages, 1 table

http://arxiv.org/abs/1209.4606
Addendum to "A Renormalizable 4-Dimensional Tensor Field Theory"
Joseph Ben Geloun, Vincent Rivasseau
(Submitted on 20 Sep 2012)
This note fills a gap in the article with title above [1]. We provide the proof of Equation (82) of Lemma 5 in [1] and thereby complete its power counting analysis with a more precise next-to-leading-order estimate.
10 pages, 4 figures

 

[marcus]

http://arxiv.org/abs/1209.4892
On the role of the Barbero-Immirzi parameter in discrete quantum gravity
Bianca Dittrich, James P. Ryan
(Submitted on 21 Sep 2012)
The 1-parameter family of transformations identified by Barbero and Immirzi plays a significant role in non-perturbative approaches to quantum gravity, among them Loop Quantum Gravity and Spin Foams. It facilitates the loop quantization programme and subsequently the Barbero-Immirzi parameter (gamma) arises in both the spectra of geometrical operators and in the dynamics provided by Spin Foams. However, the debate continues as to whether quantum physics should be Barbero-Immirzi parameter dependent. Starting from a discrete SO(4)-BF theory phase space, we find two possible reductions with respect to a discrete form of the simplicity constraints. The first reduces to a phase space with gamma-dependent symplectic structure and more generally in agreement with the phase space underlying Loop Quantum Gravity restricted to a single graph - a.k.a. Twisted Geometries. The second, fuller reduction leads to a gamma-independent symplectic structure on the phase space of piecewise-flat-linear geometries - a.k.a. Regge geometries. Thus, the gamma-dependence of physical predictions is related to the choice of phase space underlying the quantization.
16 + 12 pages

brief mention:
http://arxiv.org/abs/1209.4786
Spectral dimension flow on continuum random multigraph
Georgios Giasemidis, John F. Wheater, Stefan Zohren
(Submitted on 21 Sep 2012)
We review a recently introduced effective graph approximation of causal dynamical triangulations (CDT), the multigraph ensemble. We argue that it is well suited for analytical computations and that it captures the physical degrees of freedom which are important for the reduction of the spectral dimension as observed in numerical simulations of CDT. ...
6 pages, 1 figure, to appear in the Proceedings of Sixth International School on Field Theory and Gravitation 2012 (Petropolis, Brazil)

http://arxiv.org/abs/1209.4798
Aspects of dynamical dimensional reduction in multigraph ensembles of CDT
Georgios Giasemidis, John F. Wheater, Stefan Zohren
(Submitted on 21 Sep 2012)
We study the continuum limit of a "radially reduced" approximation of Causal Dynamical Triangulations (CDT), so-called multigraph ensembles, and explain why they serve as realistic toy models to study the dimensional reduction observed in numerical simulations of four-dimensional CDT...
4 pages, 1 figure, Presented at "Gravity, Quantum, and Black Holes" session of IC-MSQUARE 2012, Budapest

 

[John86]

http://arxiv.org/abs/1209.5284
The Tensor Track: an Update
Vincent Rivasseau
(Submitted on 24 Sep 2012)
The tensor track approach to quantum gravity is based on a new class of quantum field theories, called tensor group field theories (TGFTs). We provide a brief review of recent progress and list some desirable properties of TGFTs. In order to narrow the search for interesting models, we also propose a set of guidelines for TGFT's loosely inspired by the Osterwalder-Schrader axioms of ordinary Euclidean QFT.

http://arxiv.org/abs/1209.5060
C*-algebras of Holonomy-Diffeomorphisms & Quantum Gravity I
Johannes Aastrup, Jesper M. Grimstrup
(Submitted on 23 Sep 2012)
A new approach to a unified theory of quantum gravity based on noncommutative geometry and canonical quantum gravity is presented. The approach is built around a *-algebra generated by local holonomy-diffeomorphisms on a 3-manifold and a quantized Dirac type operator; the two capturing the kinematics of quantum gravity formulated in terms of Ashtekar variables. We prove that the separable part of the spectrum of the algebra is contained in the space of measurable connections modulo gauge transformations and we give limitations to the non-separable part. The construction of the Dirac type operator -- and thus the application of noncommutative geometry -- is motivated by the requirement of diffeomorphism invariance. We conjecture that a semi-finite spectral triple, which is invariant under volume-preserving diffeomorphisms, arise from a GNS construction of a semi-classical state. Key elements of quantum field theory emerge from the construction in a semi-classical limit, as does an almost commutative algebra. Finally, we note that the spectrum of loop quantum gravity emerges from a discretization of our construction. Certain convergence issues are left unresolved. This paper is the first of two where the second paper is concerned with mathematical details and proofs concerning the spectrum of the holonomy-diffeomorphism algebra.

http://arxiv.org/abs/1209.5057
C*-algebras of Holonomy-Diffeomorphisms & Quantum Gravity II
Johannes Aastrup, Jesper M. Grimstrup
(Submitted on 23 Sep 2012)
We introduce the holonomy-diffeomorphism algebra, a C*-algebra generated by flows of vectorfields and the compactly supported smooth functions on a manifold. We show that the separable representations of the holonomy-diffeomorphism algebra are given by measurable connections, and that the unitary equivalence of the representations corresponds to measured gauge equivalence of the measurable connections. We compare the setup to Loop Quantum Gravity and show that the generalized connections found there are not contained in the spectrum of the holonomy-diffeomorphism algebra in dimensions higher than one. This is the second paper of two, where the prequel gives an exposition of a framework of quantum gravity based on the holonomy-diffeomorphism algebra.

http://arxiv.org/abs/1209.4948
Processing quantum information with relativistic motion of atoms
Eduardo Martin-Martinez, David Aasen, Achim Kempf
(Submitted on 22 Sep 2012)
We show that particle detectors, such as 2-level atoms, in non-inertial motion (or in gravitational fields) could be used to build quantum gates for the processing of quantum information. Concretely, we show that through suitably chosen non-inertial trajectories of the detectors the interaction Hamiltonian's time dependence can be modulated to yield arbitrary rotations in the Bloch sphere due to relativistic quantum effects.

http://arxiv.org/abs/1209.5196
Evidence for Bohmian velocities from conditional Schrodinger equation
H. Nikolic
(Submitted on 24 Sep 2012)
It is often argued that measurable predictions of Bohmian mechanics cannot be distinguished from those of a theory with arbitrarily modified particle velocities satisfying the same equivariance equation. By considering the wave function of a closed system in a state with definite total energy, we argue that a distinction in measurable predictions is possible. Even though such a wave function is time-independent, the conditional wave function for a subsystem depends on time through the time-dependent particle trajectories not belonging to the subsystem. If these trajectories can be approximated by classical trajectories, then the conditional wave function can be approximated by a wave function which satisfies Schrodinger equation in a classical time-dependent potential, which is in good agreement with observations. However, such an approximation cannot be justified for particle velocities significantly deviating from the Bohmian ones, implying that Bohmian velocities are observationally preferred.

http://arxiv.org/abs/1209.5271
Using Newton's Law for Dark Energy
Paul Frampton
(Submitted on 24 Sep 2012)
A model is introduced in which Newton's law is modified between matter and dark energy corpuscles (DECs). The model predicts that the DEC component is presently decelerating in its expansion at 14% of the magnitude of the matter expansion acceleration. In the future, expansion of the DEC universe will continue to decelerate.

 

[marcus]

This paper is very beautiful. Clear writing makes it broadly understandable (partly John Baez influence on Derek I imagine):
http://arxiv.org/abs/1210.0019
Lifting General Relativity to Observer Space
Steffen Gielen, Derek K. Wise
(Submitted on 28 Sep 2012)
The 'observer space' of a Lorentzian spacetime is the space of future-timelike unit tangent vectors. Using Cartan geometry, we first study the structure a given spacetime induces on its observer space, then use this to define abstract observer space geometries for which no underlying spacetime is assumed. We propose taking observer space as fundamental in general relativity, and prove integrability conditions under which spacetime can be reconstructed as a quotient of observer space. Additional field equations on observer space then descend to Einstein's equations on the reconstructed spacetime. We also consider the case where no such reconstruction is possible, and spacetime becomes an observer-dependent, relative concept. Finally, we discuss applications of observer space, including a geometric link between covariant and canonical approaches to gravity.
34 pages

http://arxiv.org/abs/1210.0418
Interpretation of the triad orientations in loop quantum cosmology
Claus Kiefer, Christian Schell
(Submitted on 1 Oct 2012)
Loop quantum cosmology allows for arbitrary superpositions of the triad variable. We show here how these superpositions can become indistinguishable from a classical mixture by the interaction with fermions. We calculate the reduced density matrix for a locally rotationally symmetric Bianchi I model and show that the purity factor for the triads decreases by decoherence. In this way, the Universe assumes a definite orientation.
12 pages, 1 figure

Late addition, somehow overlooked in July when it came out:
http://arxiv.org/abs/1207.6734
Renormalization of Tensorial Group Field Theories: Abelian U(1) Models in Four Dimensions
Sylvain Carrozza, Daniele Oriti, Vincent Rivasseau
(Submitted on 28 Jul 2012)
We tackle the issue of renormalizability for Tensorial Group Field Theories (TGFT) including gauge invariance conditions, with the rigorous tool of multi-scale analysis, to prepare the ground for applications to quantum gravity models. In the process, we define the appropriate generalization of some key QFT notions, including: connectedness, locality and contraction of (high) subgraphs. We also define a new notion of Wick ordering, corresponding to the subtraction of (maximal) melonic tadpoles. We then consider the simplest examples of dynamical 4-dimensional TGFT with gauge invariance conditions for the Abelian U(1) case. We prove that they are super-renormalizable for any polynomial interaction.
33 pages, 8 figures
EDIT: I now see that this was added to the bibliography when it came out, in post #1781,
https://www.physicsforums.com/showthread.php?p=4016291#post4016291
but I overlooked it when sifting thru the quarter's papers to assemble a list for the poll.

EDIT: Tom, interesting comment about Kiefer! I had a vague notion of him as an independent, able to do research in LQG and make a significant contribution, but apt equally well three months later to post an article in some other branch of QG. I will look more carefully now.

 

[tom.stoer]

Claus Kiefer is joining the LQC community ...

 

[marcus]

http://arxiv.org/abs/1210.0849
The polymer quantization in LQG: massless scalar field
Marcin Domagala, Michal Dziendzikowski, Jerzy Lewandowski
(Submitted on 2 Oct 2012)
The polymer quantization of matter fields is a diffeomorphism invariant framework compatible with Loop Quantum Gravity. Whereas studied by itself, it is not explicitly used in the known completely quantizable models of matter coupled to LQG. In the current paper we apply the polymer quantization to the model of massless scalar field coupled to LQG. We show that the polymer Hilbert space of the field degrees of freedom times the LQG Hilbert space of the geometry degrees of freedom admit the quantum constraints of GR and accommodate their explicit solutions. In this way the quantization can be completed. That explicit way of solving the quantum constraints suggests interesting new ideas.
19 pages, no figures, Contribution to the Proceedings of the 3rd Quantum Geometry and Quantum Gravity School in Zakopane (2011)

briefly noted, possibly of general interest:
http://arxiv.org/abs/1210.0544
Dark matter and cosmic structure
Carlos S. Frenk, Simon D. M. White
(Submitted on 1 Oct 2012)
We review the current standard model for the evolution of cosmic structure, tracing its development over the last forty years and focusing specifically on the role played by numerical simulations and on aspects related to the nature of dark matter.
27 pages. Invited review in Annalen der Physik - www.ann-phys.org

 

[marcus]

briefly noted:
http://arxiv.org/abs/1210.0944
Reverse Engineering Quantum Field Theory
Robert Oeckl (CCM-UNAM)
(Submitted on 2 Oct 2012)
An approach to the foundations of quantum theory is advertised that proceeds by "reverse engineering" quantum field theory. As a concrete instance of this approach, the general boundary formulation of quantum theory is outlined.
5 pages,

 

[marcus]

http://arxiv.org/abs/1210.1485
Loop Quantum Gravity Phenomenology: Linking Loops to Physics
Florian Girelli, Franz Hinterleitner, Seth Major
(Submitted on 4 Oct 2012)
Research during the last decade demonstrates that effects originating on the Planck scale are currently being tested in multiple observational contexts. In this review we discuss quantum gravity phenomenological models and their possible links to loop quantum gravity. Particle frameworks, including kinematic models, broken and deformed Poincaré symmetry, non-commutative geometry, relative locality and generalized uncertainty principle, and field theory frameworks, including Lorentz violating operators in effective field theory and non-commutative field theory, are discussed. The arguments relating loop quantum gravity to models with modified dispersion relations are reviewed, as well as, arguments supporting the preservation of local Lorentz invariance. The phenomenology related to loop quantum cosmology is briefly reviewed, with a focus on possible effects that might be tested in the near future. As the discussion makes clear, there remains much interesting work to do in establishing the connection, or lack thereof, between the fundamental theory of loop quantum gravity and these specific phenomenological models, in determining observational consequences of the characteristic aspects of loop quantum gravity, and in further refining current observations. Open problems related to these developments are highlighted.
75 pages. 2 figures. Invited review for SIGMA Special Issue "Loop Quantum Gravity and Cosmology"

http://arxiv.org/abs/1210.1528
Experimentally testing asymptotically safe quantum gravity with photon-photon scattering
Astrid Eichhorn
(Submitted on 4 Oct 2012)
Matter-quantum gravity interactions can be used for direct and also indirect experimental tests of quantum gravity. We focus on photon-photon scattering in asymptotically safe gravity as a direct test of the small-scale structure of spacetime, and discuss how near-future experiments can probe asymptotic safety in a setting with large extra dimensions.
3 pages. Prepared for the proceedings of the 13th Marcel Grossmann meeting

 

[marcus]

http://arxiv.org/abs/1210.1787
Spontaneous breaking of Lorentz symmetry for canonical gravity
Steffen Gielen
(Submitted on 5 Oct 2012)
In the Ashtekar-Barbero formulation of canonical general relativity based on an SU(2) connection, Lorentz covariance is a subtle issue which has been the focus of some debate. Here we present a Lorentz covariant formulation generalising the notion of a foliation of spacetime to a field of local observers which specify a time direction only locally. This field spontaneously breaks the local SO(3,1) symmetry down to a subgroup SO(3); we show that the apparent symmetry breaking to SO(3) is not in conflict with Lorentz covariance. We give a geometric picture of our construction as Cartan geometrodynamics and outline further applications of the formalism of local observers, motivating the idea that observer space, instead of spacetime, should serve as the fundamental arena for gravitational physics.
8 pages, contribution to the proceedings of the conference "Relativity and Gravitation - 100 years after Einstein in Prague"

 

[MTd2]

We missed this one ... I found here:

http://www.technologyreview.com/view/429528/topology-the-secret-ingredient-in-the-latest/?ref=rss

http://arxiv.org/abs/1210.1281

Topological order: from long-range entangled quantum matter to an unification of light and electrons

Xiao-Gang Wen
(Submitted on 4 Oct 2012)
In primary school, we were told that there are four states of matter: solid, liquid, gas, and plasma. In college, we learned that there are much more then four states of matter. For example, the phenomenon of magnetization reveals the existence of ferromagnetic phases and the phenomenon of zero-viscosity reveals the existence of superfluid phases. There many more phases in our rich world, and it is amazing that those phases can be understood systematically by the symmetry breaking theory of Landau. In this paper, we will review the progress in last 20 -- 30 years, during which we discovered that there are many new phases that cannot be described Landau symmetry breaking theory. We discuss new "topological" phenomena, such as topological degeneracy, that reveal the existence of those new phases -- topologically ordered phases. Just like zero-viscosity define the superfluid order, the new "topological" phenomena define the topological order at macroscopic level. More recently, we find that, at microscopical level, topological order is due to long-range quantum entanglements, just like fermion superfluid is due to fermion-pair condensation. Long-range quantum entanglements lead to many amazing emergent phenomena, such as fractional quantum numbers, fractional/non-Abelian statistics, and protected gapless boundary excitations. We find that long-range quantum entanglements (or topological order) provide a unified origin of light and electrons: light waves are fluctuations of long-range entanglements, and fermions are defects of long-range entanglements. Long-range quantum entanglements (and the related topological order) represent a new chapter and a future direction of condensed matter physics, or even physics in general.

 

[marcus]

http://arxiv.org/abs/1210.2252
The scaling of black hole entropy in loop quantum gravity
Amit Ghosh, Alejandro Perez
(Submitted on 8 Oct 2012)
We discuss some general properties of black hole entropy in loop quantum gravity from the perspective of local stationary observers at distance l from the horizon. The present status of the theory indicates that black hole entropy differs from the low energy (IR) expected value A/(4G) (in natural units) in the deep Planckian regime (UV). The partition function is well defined if the number of non-geometric degrees of freedom g_M(encoding the degeneracy of the area a_p eigenvalue at a puncture p) satisfy the holographic bound g_M < exp(a_p/(4G)). Our framework provides a natural renormalization mechanism such that S_UV ---> S_IR=A/(4G_Newton) as the scale l flows.
7 pages.

[my comment: notice that G is running with energy in this paper, as I read it only in the IR limit do we have G=G_Newton ]

 

[John86]

http://arxiv.org/abs/1210.2589
Everpresent Lambda - II
Maqbool Ahmed, Rafael Sorkin
(Submitted on 9 Oct 2012)
Ideas from causal set theory lead to a fluctuating, time dependent cosmological-constant of the right order of magnitude to match currently quoted "dark energy" values. Although such a term was predicted some time ago, a more detailed analysis of the resulting class of phenomenological models was begun only recently (based on numerical simulation of the cosmological equations with such a fluctuating term). In this paper we continue the investigation by studying the sensitivity of the scheme to some of the ad hoc choices made in setting it up.

 

[tom.stoer]

Updated:

http://arxiv.org/abs/1004.2260
The new vertices and canonical quantization
Authors: Sergei Alexandrov
(Submitted on 13 Apr 2010 (v1), last revised 25 Jun 2010 (this version, v3))
Abstract: We present two results on the recently proposed new spin foam models. First, we show how a (slightly modified) restriction on representations in the EPRL model leads to the appearance of the Ashtekar-Barbero connection, thus bringing this model even closer to LQG. Second, we however argue that the quantization procedure used to derive the new models is inconsistent since it relies on the symplectic structure of the unconstraint BF theory.

 

[marcus]

http://arxiv.org/abs/1210.3372
Statistical mechanics of graph models and their implications for emergent manifolds
Si Chen, Steven S. Plotkin
(Submitted on 11 Oct 2012)
Inspired by "quantum graphity" models for spacetime, a statistical model of graphs is proposed to explore possible realizations of emergent manifolds. Graphs with given numbers of vertices and edges are considered, governed by a very general Hamiltonian that merely favors graphs with near-constant valency and local rotational symmetry. The ratio of vertices to edges controls the dimensionality of the emergent manifold. The model is simulated numerically in the canonical ensemble for a given vertex to edge ratio, where it is found that the low energy states are almost triangulations of two dimensional manifolds. The resulting manifold shows topological "handles" and surface intersections in a higher embedding space as well as non-trivial fractal dimension. The transition is first order, underlying the difficulty of graph models in describing criticality that is independent of the details of the underlying graph. Another interesting phenomenon is that the entropy of the graphs are super-extensive, a fact known since Erdös, which results in a transition temperature of zero in the limit of infinite system size: infinite manifolds are always disordered. Aside from a finite universe or diverging coupling constraints as possible solutions to this problem, long-range interactions between vertex defects also resolve the problem and restore a non-zero transition temperature, in a manner similar to that in low-dimensional condensed-matter systems.
19 pages, 19 figures, 1 table

 

[marcus]

http://arxiv.org/abs/1210.3960
Constraint algebra in LQG reloaded : Toy model of an Abelian gauge theory - II Spatial Diffeomorphisms
Adam Henderson, Alok Laddha, Casey Tomlin
(Submitted on 15 Oct 2012)
In [1] we initiated an approach towards quantizing the Hamiltonian constraint in Loop Quantum Gravity (LQG) by requiring that it generates an anomaly-free representation of constraint algebra off-shell. We investigated this issue in the case of a toy model of a 2+1-dimensional U(1)³ gauge theory, which can be thought of as a weak coupling limit of Euclidean three dimensional gravity. However in [1] we only focused on the most non-trivial part of the constraint algebra that involves commutator of two Hamiltonian constraints. In this paper we continue with our analysis and obtain a representation of full constraint algebra in loop quantized framework. We show that there is a representation of the Diffeomorphism group with respect to which the Hamiltonian constraint quantized in [1] is diffeomorphism covariant. Our work can be thought of as a potential first step towards resolving some long standing issues with the Hamiltonian constraint in canonical LQG.
30 pages, 1 figure
My comment: previous paper = http://arxiv.org/abs/1204.0211

Brief mention (possible general interest):
http://arxiv.org/abs/1210.3624
A Correlation Between the Higgs Mass and Dark Matter
Mark P. Hertzberg (MIT)
(Submitted on 12 Oct 2012)
Depending on the value of the Higgs mass, the Standard Model acquires an unstable region at large Higgs field values due to RG running of couplings, which we evaluate at 2-loop. For currently favored values of the Higgs mass, this renders the electroweak vacuum only meta-stable with a long lifetime. We argue on statistical grounds that the Higgs field would be highly unlikely to begin in the small field meta-stable region in the early universe, and thus some new physics should enter in the energy range of order, or lower than, the instability scale to remove the large field unstable region. We assume that Peccei-Quinn (PQ) dynamics enters to solve the strong CP problem and, for a PQ-scale in this energy range, may also remove the unstable region. We allow the PQ-scale to scan and argue, again on statistical grounds, that its value in our universe should be of order the instability scale, rather than (significantly) lower. Since the Higgs mass determines the instability scale, which is argued to set the PQ-scale, and since the PQ-scale determines the axion properties, including its dark matter abundance, we are led to a correlation between the Higgs mass and the abundance of dark matter. We find the correlation to be in good agreement with current data.
9 pages, 3 figures

http://arxiv.org/abs/1210.4026
Covariant multi-galileons and their generalisation
Antonio Padilla, Vishagan Sivanesan
(Submitted on 15 Oct 2012)
We find a covariant completion of the flat-space multi-galileon theory, preserving second-order field equations. We then generalise this to arrive at an enlarged class of second order theories describing multiple scalars and a single tensor, and conjecture that these are a multi-scalar version of Horndeski's most general scalar-tensor theory.
11 pages
My comment: Padilla's way to distinguish vacuum curvature (Cosmo Const.) from vacuum energy.

http://arxiv.org/abs/1210.4128
Comment on "Quantum Time Crystals": a new paradigm or just another proposal of perpetuum mobile?
Patrick Bruno
(Submitted on 15 Oct 2012)
A Comment on Frank Wilczek's paper "Quantum Time Crystals" (Phys. Rev. Lett. 109, 160401 (2012); arXiv:1202.2539).
1 page

 

[marcus]

http://arxiv.org/abs/1210.4504
A new perspective on cosmology in Loop Quantum Gravity
Emanuele Alesci, Francesco Cianfrani
(Submitted on 16 Oct 2012)
We present a new cosmological model derived from Loop Quantum Gravity. The formulation is based on a projection of the kinematical Hilbert space of the full theory down to a subspace representing the proper arena for an inhomogeneous Bianchi I model. This procedure gives a direct link between the full theory and its cosmological sector. The emerging quantum cosmological model represents a simplified arena on which the complete canonical quantization program can be tested. The achievements of this analysis could also shed light on Loop Quantum Cosmology and its relation with the full theory.
5 pages

Brief mention:
http://arxiv.org/abs/1210.4174
The Physical Principle that determines the Value of the Cosmological Constant
T. Padmanabhan
(Submitted on 15 Oct 2012)
Observations indicate that the evolution of our universe can be divided into three epochs consisting of early time inflation, radiation (and matter) domination and the late time acceleration. One can associate with each of these epochs a number N which is the phase space volume of the modes which cross the Hubble radius during the corresponding epoch. This number turns out to be (approximately) the same for the cosmologically relevant ranges of the three epochs. When the initial de Sitter space is characterized by the Planck length, the natural value for N is 4π. This allows us to determine the cosmological constant which drives the late time acceleration, to be Λ L²_P = 3exp(-24π²μ) where μ is a number of order unity. This expression leads to the observed value of cosmological constant for μ ~ 1.19. The implications are discussed.
9 pages; 1 figure

 

[John86]

Interesting !..http://arxiv.org/abs/1206.4949
Fundamental quantum optics experiments conceivable with satellites -- reaching relativistic distances and velocities
David Rideout, Thomas Jennewein, Giovanni Amelino-Camelia, Tommaso F. Demarie, Brendon L. Higgins, Achim Kempf, Adrian Kent, Raymond Laflamme, Xian Ma, Robert B. Mann, Eduardo Martin-Martinez, Nicolas C. Menicucci, John Moffat, Christoph Simon, Rafael Sorkin, Lee Smolin, Daniel R. Terno
(Submitted on 21 Jun 2012 (v1), last revised 5 Oct 2012 (this version, v2))
Physical theories are developed to describe phenomena in particular regimes, and generally are valid only within a limited range of scales. For example, general relativity provides an effective description of the Universe at large length scales, and has been tested from the cosmic scale down to distances as small as 10 meters. In contrast, quantum theory provides an effective description of physics at small length scales. Direct tests of quantum theory have been performed at the smallest probeable scales at the Large Hadron Collider, ${\sim} 10^{-20}$ meters, up to that of hundreds of kilometers. Yet, such tests fall short of the scales required to investigate potentially significant physics that arises at the intersection of quantum and relativistic regimes. We propose to push direct tests of quantum theory to larger and larger length scales, approaching that of the radius of curvature of spacetime, where we begin to probe the interaction between gravity and quantum phenomena. In particular, we review a wide variety of potential tests of fundamental physics that are conceivable with artificial satellites in Earth orbit and elsewhere in the solar system, and attempt to sketch the magnitudes of potentially observable effects. The tests have the potential to determine the applicability of quantum theory at larger length scales, eliminate various alternative physical theories, and place bounds on phenomenological models motivated by ideas about spacetime microstructure from quantum gravity. From a more pragmatic perspective, as quantum communication technologies such as quantum key distribution advance into Space towards large distances, some of the fundamental physical effects discussed here may need to be taken into account to make such schemes viable.

 

[marcus]

http://arxiv.org/abs/1210.5223
Experimental search for a Lorentz invariant spacetime granularity: Possibilities and bounds
Pedro Aguilar, Yuri Bonder, Daniel Sudarsky
(Submitted on 18 Oct 2012)
We consider a search for phenomenological signatures from an hypothetical space-time granularity that respects Lorentz invariance. The model is based on the idea that the metric description of Einstein's gravity corresponds to a hydrodynamic characterization of some deeper underlying structure, and that Einstein's gravity is thus to be seen as emergent. We present the specific phenomenological model in detail and analyze the bounds on its free parameters established by a experiment specifically designed to test this model.
25 pages

Brief mention:
http://arxiv.org/abs/1210.4940
Thermodynamics of universal horizons in Einstein-aether theory
Per Berglund, Jishnu Bhattacharyya, David Mattingly
(Submitted on 17 Oct 2012)
... This suggests that the class of holographic theories may be much broader than currently assumed.
5 pages.

 

[marcus]

http://arxiv.org/abs/1210.5276
Geometric asymptotics for spin foam lattice gauge gravity on arbitrary triangulations
Frank Hellmann, Wojciech Kaminski
(Submitted on 18 Oct 2012)
We study the behavior of holonomy spin foam partition functions, a form of lattice gauge gravity, on generic 4d-triangulations using micro local analysis. To do so we adapt tools from the renormalization theory of quantum field theory on curved space times. This allows us, for the first time, to study the partition function without taking any limits on the interior of the triangulation.
We establish that for many of the most widely used models the geometricity constraints, which reduce the gauge theory to a geometric one, introduce strong accidental curvature constraints. These limit the curvature around each triangle of the triangulation to a finite set of values. We demonstrate how to modify the partition function to avoid this problem. Finally the new methods introduced provide a starting point for studying the regularization ambiguities and renormalization of the partition function.
4+6 pages, 1 figure

Brief mention:
http://arxiv.org/abs/1210.5490
Asymptotic Freedom of Rank 4 Tensor Group Field Theory
Joseph Ben Geloun
(Submitted on 19 Oct 2012)
Recently, a rank four tensor group field theory has been proved renormalizable. We provide here the key points on the renormalizability of this model and its UV asymptotic freedom.
7 pages, 3 Figures; Contribution to the XXIXth International Colloquium on Group-Theoretical Methods in Physics, Nankai, China, August 20-26, 2012

http://arxiv.org/abs/1210.5317
Comment on the black hole firewall
Sabine Hossenfelder
(Submitted on 19 Oct 2012)
Recently, it has been argued that black hole complementarity is inconsistent by showing that, for an infalling observer, it would lead to the existence of a firewall near the black hole horizon, thereby violating the equivalence principle. If true, this would necessitate to give up on at least one of the postulates of black hole complementarity. In this comment I want to address an additional assumption that went into the conclusion, that the early outgoing Hawking radiation is entangled with the late radiation.

 

[marcus]

http://arxiv.org/abs/1210.6257
Group field theories
Thomas Krajewski
(Submitted on 23 Oct 2012)
Group field theories are particular quantum field theories defined on D copies of a group which reproduce spin foam amplitudes on a space-time of dimension D. In these lecture notes, we present the general construction of group field theories, merging ideas from tensor models and loop quantum gravity. This lecture is organized as follows. In the first section, we present basic aspects of quantum field theory and matrix models. The second section is devoted to general aspects of tensor models and group field theory and in the last section we examine properties of the group field formulation of BF theory and the EPRL model. We conclude with a few possible research topics, like the construction of a continuum limit based on the double scaling limit or the relation to loop quantum gravity through Schwinger-Dyson equations
58 pages. Lectures given at the "3rd Quantum Gravity and Quantum Geometry School", March 2011, Zakopane

http://arxiv.org/abs/1210.6215
Pure connection formalism for gravity: Feynman rules and the graviton-graviton scattering
Gianluca Delfino, Kirill Krasnov, Carlos Scarinci
(Submitted on 23 Oct 2012)
We continue to develop the pure connection formalism for gravity. We derive the Feynman rules for computing the connection correlation functions, as well as the prescription for obtaining the Minkowski space graviton scattering amplitudes from the latter. The present formalism turns out to be significantly simpler than the one based on the metric in many aspects. The most drastic difference with the usual approach is that the conformal factor of the metric, which is a source of difficulties in the metric treatment, does not propagate in the connection formulation even off-shell. This simplifies both the linearized theory and the interactions. For comparison, in our approach the complete off-shell cubic GR interaction contains just 3 terms, with only a single term relevant at tree level. This should be compared to at least a dozen terms in the metric formalism. We put the technology developed to use and compute the simplest graviton-graviton scattering amplitudes...
... This serves as a good illustration of the type of parity violation present in these theories. We find that the parity-violating amplitudes are important at high energies, and that a general parity-violating member of our class of theories "likes" one helicity (negative in our conventions) more than the other in the sense that at high energies it tends to convert all present gravitons into those of negative helicity.
46 pages.

my comment: For context here is a quote from page 1.

In paper [1] one of us showed how Λ≠ 0 General Relativity (GR) can be described in the ”pure connection” formalism, in which the only field present in the Lagrangian formulation of the theory is a (complexified) SO(3) connection rather than the metric. Paper [2] made the first steps towards setting up the perturbation theory in this formalism, analyzing the free theory and obtaining the propagator...​

For additional context.

[1] K. Krasnov, “Pure Connection Action Principle for General Relativity,” Phys. Rev. Lett. 106, 251103 (2011) [arXiv:1103.4498 [gr-qc]].
[2] K. Krasnov, “Gravity as a diffeomorphism invariant gauge theory,” Phys. Rev. D 84, 024034 (2011) [arXiv:1101.4788 [hep-th]].
[3] R. Capovilla, T. Jacobson and J. Dell, “General Relativity Without the Metric,” Phys. Rev. Lett. 63, 2325 (1989).
[4] R. Capovilla, T. Jacobson and J. Dell, “A Pure spin connection formulation of gravity,” Class. Quant. Grav. 8, 59 (1991).​

http://arxiv.org/abs/1210.5621
Towards solving generic cosmological singularity problem
Wlodzimierz Piechocki
(Submitted on 20 Oct 2012)
The big bounce transition of the quantum FRW model in the setting of loop quantum cosmology is presented. We determine the physical self-adjoint Hamiltonian generating the dynamics. It is used to define, via the Stone theorem, an evolution operator. We examine properties of expectation values of physical observables in the process of the quantum big bounce transition. The dispersion of observables are studied in the context of the Heisenberg uncertainty principle. We suggest that the real nature of the bounce may become known only after we quantize the Belinskii-Khalatnikov-Lifgarbagez scenario, which concerns the generic cosmological singularity.
4 pages, no figures; talk presented at the Multiverse and Fundamental Cosmology Conference, 10-14 September, 2012, Szczecin, Poland; to be published in the AIP Conference Proceedings Series

 

[MTd2]

http://arxiv.org/abs/1210.6736

Noether current of the surface term of Einstein-Hilbert action, Virasoro algebra and entropy

Bibhas Ranjan Majhi
(Submitted on 25 Oct 2012)
A derivation of Noether current from the surface term of Einstein-Hilbert action is given. We show that the corresponding charge, calculated on the horizon, is related to the Bekenstein-Hawking entropy. Also using the charge, the same entropy is found based on the Virasoro algebra and Cardy formula approach. In this approach, the relevant diffeomorphisms are found by imposing a very simple physical argument: diffeomorphisms keep the horizon structure invariant. Finally we discuss the technical simplicities and improvements over the earlier attempts and also various important physical implications.

 

[marcus]

http://arxiv.org/abs/1210.7222
Solvable model for quantum gravity
Jack Gegenberg, Viqar Husain
We study a type of geometric theory with a non-dynamical one-form field. For a manifold that is R⁴, this is equivalent to a theory formulated on a symplectic manifold. Its dynamical variables are an su(2) gauge field and a triad of su(2) valued one-forms. Hamiltonian decomposition reveals that the theory has a true Hamiltonian, together with spatial diffeomorphism and Gauss law constraints, which generate the only local symmetries. Although perturbatively non-renormalizable, the model provides a test bed for the non-perturbative quantization techniques of loop quantum gravity.

http://arxiv.org/abs/1210.6869
Towards an Anomaly-Free Quantum Dynamics for a Weak Coupling Limit of Euclidean Gravity
Casey Tomlin, Madhavan Varadarajan
The G -->0 limit of Euclidean gravity introduced by Smolin is described by a generally covariant U(1)xU(1)xU(1) gauge theory. The Poisson bracket algebra of its Hamiltonian and diffeomorphism constraints is isomorphic to that of gravity. Motivated by recent results in Parameterized Field Theory and by the search for an anomaly-free quantum dynamics for Loop Quantum Gravity (LQG), the quantum Hamiltonian constraint of density weight 4/3 for this U(1)xU(1)xU(1) theory is constructed so as to produce a non-trivial LQG-type representation of its Poisson brackets through the following steps. First, the constraint at finite triangulation, as well as the commutator between a pair of such constraints, are constructed as operators on the 'charge' network basis. Next, the continuum limit of the commutator is evaluated with respect to an operator topology defined by a certain space of `vertex smooth' distributions. Finally, the operator corresponding to the Poisson bracket between a pair of Hamiltonian constraints is constructed at finite triangulation in such a way as to generate a `generalised' diffeomorphism and its continuum limit is shown to agree with that of the commutator between a pair of finite triangulation Hamiltonian constraints. Our results in conjunction with the recent work of Henderson, Laddha and Tomlin in a 2+1-dimensional context, constitute the necessary first steps toward a satisfactory treatment of the quantum dynamics of this model
57 pages 9 figures.

http://arxiv.org/abs/1210.6877
Towards an Anomaly-Free Quantum Dynamics for a Weak Coupling Limit of Euclidean Gravity: Diffeomorphism Covariance
Madhavan Varadarajan
The G-->0 limit of Euclidean gravity introduced by Smolin is described by a generally covariant U(1)xU(1)xU(1) gauge theory. In an earlier paper, Tomlin and Varadarajan constructed the quantum Hamiltonian constraint of density weight 4/3 for this U(1)xU(1)xU(1) theory so as to produce a non-trivial anomaly free LQG-type representation of the Poisson bracket between a pair of Hamiltonian constraints. These constructions involved a choice of regulating coordinate patches. The use of these coordinate patches is in apparent conflict with spatial diffeomorphism covariance. In this work we show how an appropriate choice of coordinate patches together with suitable modifications of these constructions results in the diffeomorphism covariance of the continuum limit action of the Hamiltonian constraint operator, while preserving the anomaly free property of the continuum limit action of its commutator.
56 pages.

 

[marcus]

http://arxiv.org/abs/1210.7248
Loop Quantum Cosmology: Anisotropy and singularity resolution
Alejandro Corichi, Asieh Karami, Edison Montoya
(Submitted on 26 Oct 2012)
In this contribution we consider the issue of singularity resolution within loop quantum cosmology (LQC) for different homogeneous models. We present results of numerical evolutions of effective equations for both isotropic as well as anisotropic cosmologies, with and without spatial curvature. To address the issue of singularity resolution we examine the time evolution of geometrical and curvature invariants that yield information about the semiclassical spacetime geometry. We discuss generic behavior found for a variety of initial conditions. Finally, we show that the modifications which come from Loop Quantum Cosmology imply a non-chaotic effective behavior in the vacuum Bianchi IX model.
12 pages, 4 figures, To appear in the Proceedings of the Relativity and Gravitation 100 Years after Einstein in Prague

http://arxiv.org/abs/1210.7596
The trouble with asymptotically safe inflation
Chao Fang, Qing-Guo Huang
(Submitted on 29 Oct 2012)
In this paper we investigate the perturbation theory of the asymptotically safe inflation and we find that all modes of gravitational waves perturbation become ghosts in order to achieve a large enough number of e-folds. Formally we can calculate the power spectrum of gravitational waves perturbation, but we find that it is negative. It indicates that there is serious trouble with the asymptotically safe inflation.
13 pages, 1 figure

 

[marcus]

http://arxiv.org/abs/1210.8138
Non-linear (loop) quantum cosmology
Martin Bojowald, Alexander L. Chinchilli, Christine C. Dantas, Matthew Jaffe, David Simpson
(Submitted on 30 Oct 2012)
Inhomogeneous quantum cosmology is modeled as a dynamical system of discrete patches, whose interacting many-body equations can be mapped to a non-linear minisuperspace equation by methods analogous to Bose-Einstein condensation. Complicated gravitational dynamics can therefore be described by more-manageable equations for finitely many degrees of freedom, for which powerful solution procedures are available, including effective equations. The specific form of non-linear and non-local equations suggests new questions for mathematical and computational investigations, and general properties of non-linear wave equations lead to several new options for physical effects and tests of the consistency of loop quantum gravity. In particular, our quantum cosmological methods show how sizeable quantum corrections in a low-curvature universe can arise from tiny local contributions adding up coherently in large regions.
20 pages

brief mention:
http://arxiv.org/abs/1210.3545
Models of Topology Change
Alfred D. Shapere, Frank Wilczek, Zhaoxi Xiong
(Submitted on 12 Oct 2012)
We show how changes in unitarity-preserving boundary conditions allow continuous interpolation among the Hilbert spaces of quantum mechanics on topologically distinct manifolds. We present several examples, including a computation of entanglement entropy production. We discuss approximate realization of boundary conditions through appropriate interactions, thus suggesting a route to possible experimental realization. We give a theoretical application to quantization of singular Hamiltonians, and give tangible form to the "many worlds" interpretation of wave functions.
7 pages, 3 figures

http://arxiv.org/abs/1210.7834
The DSR-deformed relativistic symmetries and the relative locality of 3D quantum gravity
Giovanni Amelino-Camelia, Michele Arzano, Stefano Bianco, Riccardo J. Buonocore
(Submitted on 29 Oct 2012)
...
12 pages, 3 figures

 

[marcus]

http://arxiv.org/abs/1211.0161
Emergent Isotropy-Breaking in Quantum Cosmology
Andrea Dapor, Jerzy Lewandowski
(Submitted on 1 Nov 2012)
We consider a massive quantum test Klein-Gordon field probing an isotropic quantum cosmological space-time in the background. The result obtained is surprising. It turns out, that despite the isotropy of the quantum gravitational field, the semi-classical metric experienced by a mode of the K-G field is non-isotropic. The anisotropy depends on the direction of the momentum of the mode. Specifically, what we do is to derive a semi-classical space-time which emerges to a mode of the field. The method amounts to a comparison between QFT on a quantum background and QFT on a classical curved space-time, giving rise to an emergent metric tensor. The components of the semi-classical metric tensor are calculated from the equation of propagation of the quantum K-G field in the test field approximation. The anisotropies are of a quantum nature: they are proportional to Planck constant and "dress" the isotropic classical space-time obtained in the classical limit.
6 pages

 

[marcus]

http://arxiv.org/abs/1211.0522
Horizon entanglement entropy and universality of the graviton coupling
Eugenio Bianchi
(Submitted on 2 Nov 2012)
We compute the low-energy variation of the horizon entanglement entropy for matter fields and gravitons in Minkowski space. While the entropy is divergent, the variation under a perturbation of the vacuum state is finite and proportional to the energy flux through the Rindler horizon. Due to the universal coupling of gravitons to the energy-momentum tensor, the variation of the entanglement entropy is universal and equal to the change in area of the event horizon divided by 4 times Newton's constant - independently from the number and type of matter fields. The physical mechanism presented provides an explanation of the microscopic origin of the Bekenstein-Hawking entropy in terms of entanglement entropy.
7 pages

 

[marcus]

http://arxiv.org/abs/1211.0823
Polymer quantization and Symmetries
Ghanashyam Date, Nirmalya Kajuri
(Submitted on 5 Nov 2012)
Polymer quantization was discovered during the construction of Loop Quantum Cosmology. For the simplest quantum theory of one degree of freedom, the implications for dynamics were studied for the harmonic oscillator as well as some other potentials. For more degrees of freedom, the possibility of continuous, kinematic symmetries arises. While these are realized on the Hilbert space of polymer quantum mechanics, their infinitesimal versions are not supported. For an invariant Hamiltonian, these symmetry realizations imply infinite degeneracy suggesting that the symmetry should be spontaneously or explicitly broken. The estimation of symmetry violations in some cases have been analysed before. Here we explore the alternative of shifting the arena to the distributional states. We discuss both the polymer quantum mechanics case as well as polymer quantized scalar field.
18 pages

http://arxiv.org/abs/1211.0825
Going beyond the Standard Model with noncommutative geometry
Thijs van den Broek, Walter D. van Suijlekom
(Submitted on 5 Nov 2012)
The derivation of the full Standard Model from noncommutative geometry has been a promising sign for possible applications of the latter in High Energy Physics. Many believe, however, that the Standard Model cannot be the final answer. We translate several demands whose origin lie in physics to the context of noncommutative geometry and use these to put constraints on the fermionic content of models. We show that the Standard Model only satisfies these demands provided it has a right-handed neutrino in each 'generation'. We also prove that the Minimal Supersymmetric Standard Model is not among the models that satisfy our constraints, but pose a solution that is a slight extension of the MSSM.
19 pages