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Cosmological Natural Selection is a testable idea for explaining why the constants in physics and cosmology----the parameters of the standard models used in the two fields----have the numerical values they do.

I expect it's important enough so that it deserves a more transparent thread heading than "Cns" which is the title of the thread Chronos already started.

CNS has been proposed as a scientific alternative to "Anthropic" views, according to which the values of the constants do not require a mechanism to explain them because if several of the key numbers were substantially larger or smaller we would not be here to observe it!

Contrary to "Anthropic" (non?)explanations, the CNS idea offers an evolutionary mechanism by which the constants may have converged on their observed values, in a fashion which has nothing to do with life or consciousness. Nothing to do, that is, except having incidentally provided the conditions needed for life as we know it as kind of side effect, or byproduct.

And the idea may be wrong, which, curiously enough, is a virtue. CNS seems able to generate predictions ruling out certain observations or experimental outcomes in the future, which, if they WERE seen, would refute CNS. this "falsifiability" is the hallmark of a scientific theory---it is predictive in the sense that there are some outcomes of future experiments which it cannot accommodate. If a theory is mushy enough to accommodate any conceivable outcome of future experiments intended to test it, then it has no predictive value. (Try to imagine performing an experiment and obtaining a result that is incompatible with the existence of conscious life! ) By contrast, CNS seems to to be predictive, hence part of empirical science instead of, say, philosophy or religion.

I'm intending this to be an informational thread about CNS, so for starters here is a short reading list borrowed from the LQG link-basket

https://www.physicsforums.com/showthread.php?p=527991#post527991

1.these two papers, and the references therein, discuss the removal of the classical BB ex-singularity in a range of cases that has gradually extended the generality of Bojowald's initial 2001 result.

http://arxiv.org/abs/gr-qc/0402053

Martin Bojowald

17 pages, 2 figures, Plenary talk at ICGC 2004

"Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from general relativity: The quantum theory is free of singularities, and there are new phenomenological scenarios for the evolution of the very early universe including inflation. We give an overview of the main effects, focussing on recent results obtained by several different groups."

http://arxiv.org/abs/gr-qc/0503020

Martin Bojowald

10 pages, 3 figures, plenary talk at VI Mexican School on Gravitation and Mathematical Physics, Nov 21-27, 2004

"Loop quantum cosmology applies techniques derived for a background independent quantization of general relativity to cosmological situations and draws conclusions for the very early universe. Direct implications for the singularity problem as well as phenomenology in the context of inflation or bouncing universes result, which will be reviewed here. The discussion focuses on recent new results for structure formation and generalizations of the methods."

2. these papers, and references therein, go towards understanding the BH ex-singularity and showing that it evolves into the BB ex-singularity:

http://arxiv.org/abs/gr-qc/0503041

Martin Bojowald, Rituparno Goswami, Roy Maartens, Parampreet Singh

4 pages, 3 figures

"Quantum gravity is expected to remove the classical singularity that arises as the end-state of gravitational collapse. To investigate this, we work with a simple toy model of a collapsing homogeneous scalar field. We show that non-perturbative semi-classical effects of Loop Quantum Gravity cause a bounce and remove the classical black hole singularity. Furthermore, we find a critical threshold scale, below which no horizon forms -- quantum gravity may exclude very small astrophysical black holes."

http://arxiv.org/abs/gr-qc/0504043

Leonardo Modesto

13 pages

"We apply the recent results in Loop Quantum Cosmology and in the resolution of Black Hole singularity to the gravitational collapse of a star. We study the dynamic of the space time in the interior of the Schwarzschild radius. In particular in our simple model we obtain the evolution of the matter inside the star and of the gravity outside the region where the matter is present. The boundary condition identify an unique time inside and outside the region where the matter is present. We consider a star during the collapse in the particular case in which inside the collapsing star we take null pressure, homogeneity and isotropy. The space-time outside the matter is homogeneous and anisotropic. We show that the space time is singularity free and that we can extend dynamically the space-time beyond the classical singularity."

3. if the models of BH collapse and BB expansion can be joined in theory then one can take seriously the CNS (cosm. nat. selection) hypothesis as a way of understanding why the basic constants in the Standard Models are what they are. The CNS theory can be tested empirically by observation and experiment. This paper discusses CNS:

http://arxiv.org/abs/hep-th/0407213

Lee Smolin

for "Universe or Multiverse", ed. by Bernard Carr et. al., to be published by Cambridge University Press.

"It is explained in detail why the Anthropic Principle (AP) cannot yield any falsifiable predictions, and therefore cannot be a part of science. Cases which have been claimed as successful predictions from the AP are shown to be not that. Either they are uncontroversial applications of selection principles in one universe (as in Dicke's argument), or the predictions made do not actually logically depend on any assumption about life or intelligence, but instead depend only on arguments from observed facts (as in the case of arguments by Hoyle and Weinberg). The Principle of Mediocrity is also examined and shown to be unreliable, as arguments for factually true conclusions can easily be modified to lead to false conclusions by reasonable changes in the specification of the ensemble in which we are assumed to be typical.

We show however that it is still possible to make falsifiable predictions from theories of multiverses, if the ensemble predicted has certain properties specified here. An example of such a falsifiable multiverse theory is cosmological natural selection. It is reviewed here and it is argued that the theory remains unfalsified. But it is very vulnerable to falsification by current observations, which shows that it is a scientific theory.

The consequences for recent discussions of the AP in the context of string theory are discussed."

I expect it's important enough so that it deserves a more transparent thread heading than "Cns" which is the title of the thread Chronos already started.

CNS has been proposed as a scientific alternative to "Anthropic" views, according to which the values of the constants do not require a mechanism to explain them because if several of the key numbers were substantially larger or smaller we would not be here to observe it!

Contrary to "Anthropic" (non?)explanations, the CNS idea offers an evolutionary mechanism by which the constants may have converged on their observed values, in a fashion which has nothing to do with life or consciousness. Nothing to do, that is, except having incidentally provided the conditions needed for life as we know it as kind of side effect, or byproduct.

And the idea may be wrong, which, curiously enough, is a virtue. CNS seems able to generate predictions ruling out certain observations or experimental outcomes in the future, which, if they WERE seen, would refute CNS. this "falsifiability" is the hallmark of a scientific theory---it is predictive in the sense that there are some outcomes of future experiments which it cannot accommodate. If a theory is mushy enough to accommodate any conceivable outcome of future experiments intended to test it, then it has no predictive value. (Try to imagine performing an experiment and obtaining a result that is incompatible with the existence of conscious life! ) By contrast, CNS seems to to be predictive, hence part of empirical science instead of, say, philosophy or religion.

I'm intending this to be an informational thread about CNS, so for starters here is a short reading list borrowed from the LQG link-basket

https://www.physicsforums.com/showthread.php?p=527991#post527991

1.these two papers, and the references therein, discuss the removal of the classical BB ex-singularity in a range of cases that has gradually extended the generality of Bojowald's initial 2001 result.

http://arxiv.org/abs/gr-qc/0402053

**Loop Quantum Cosmology: Recent Progress**Martin Bojowald

17 pages, 2 figures, Plenary talk at ICGC 2004

"Aspects of the full theory of loop quantum gravity can be studied in a simpler context by reducing to symmetric models like cosmological ones. This leads to several applications where loop effects play a significant role when one is sensitive to the quantum regime. As a consequence, the structure of and the approach to classical singularities are very different from general relativity: The quantum theory is free of singularities, and there are new phenomenological scenarios for the evolution of the very early universe including inflation. We give an overview of the main effects, focussing on recent results obtained by several different groups."

http://arxiv.org/abs/gr-qc/0503020

**The Early Universe in Loop Quantum Cosmology**Martin Bojowald

10 pages, 3 figures, plenary talk at VI Mexican School on Gravitation and Mathematical Physics, Nov 21-27, 2004

"Loop quantum cosmology applies techniques derived for a background independent quantization of general relativity to cosmological situations and draws conclusions for the very early universe. Direct implications for the singularity problem as well as phenomenology in the context of inflation or bouncing universes result, which will be reviewed here. The discussion focuses on recent new results for structure formation and generalizations of the methods."

2. these papers, and references therein, go towards understanding the BH ex-singularity and showing that it evolves into the BB ex-singularity:

http://arxiv.org/abs/gr-qc/0503041

**A black hole mass threshold from non-singular quantum gravitational collapse**Martin Bojowald, Rituparno Goswami, Roy Maartens, Parampreet Singh

4 pages, 3 figures

"Quantum gravity is expected to remove the classical singularity that arises as the end-state of gravitational collapse. To investigate this, we work with a simple toy model of a collapsing homogeneous scalar field. We show that non-perturbative semi-classical effects of Loop Quantum Gravity cause a bounce and remove the classical black hole singularity. Furthermore, we find a critical threshold scale, below which no horizon forms -- quantum gravity may exclude very small astrophysical black holes."

http://arxiv.org/abs/gr-qc/0504043

**Quantum Gravitational Collapse**Leonardo Modesto

13 pages

"We apply the recent results in Loop Quantum Cosmology and in the resolution of Black Hole singularity to the gravitational collapse of a star. We study the dynamic of the space time in the interior of the Schwarzschild radius. In particular in our simple model we obtain the evolution of the matter inside the star and of the gravity outside the region where the matter is present. The boundary condition identify an unique time inside and outside the region where the matter is present. We consider a star during the collapse in the particular case in which inside the collapsing star we take null pressure, homogeneity and isotropy. The space-time outside the matter is homogeneous and anisotropic. We show that the space time is singularity free and that we can extend dynamically the space-time beyond the classical singularity."

3. if the models of BH collapse and BB expansion can be joined in theory then one can take seriously the CNS (cosm. nat. selection) hypothesis as a way of understanding why the basic constants in the Standard Models are what they are. The CNS theory can be tested empirically by observation and experiment. This paper discusses CNS:

http://arxiv.org/abs/hep-th/0407213

**Scientific alternatives to the anthropic principle**Lee Smolin

for "Universe or Multiverse", ed. by Bernard Carr et. al., to be published by Cambridge University Press.

"It is explained in detail why the Anthropic Principle (AP) cannot yield any falsifiable predictions, and therefore cannot be a part of science. Cases which have been claimed as successful predictions from the AP are shown to be not that. Either they are uncontroversial applications of selection principles in one universe (as in Dicke's argument), or the predictions made do not actually logically depend on any assumption about life or intelligence, but instead depend only on arguments from observed facts (as in the case of arguments by Hoyle and Weinberg). The Principle of Mediocrity is also examined and shown to be unreliable, as arguments for factually true conclusions can easily be modified to lead to false conclusions by reasonable changes in the specification of the ensemble in which we are assumed to be typical.

We show however that it is still possible to make falsifiable predictions from theories of multiverses, if the ensemble predicted has certain properties specified here. An example of such a falsifiable multiverse theory is cosmological natural selection. It is reviewed here and it is argued that the theory remains unfalsified. But it is very vulnerable to falsification by current observations, which shows that it is a scientific theory.

The consequences for recent discussions of the AP in the context of string theory are discussed."

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