III. An Organic, Conducive, Habitable MultiUniVerse
4. Novel ExoUniverse Studies
I began these musings in the early 1960s when even a point of cosmic origin was not known, starry galaxies were just found a few decades before. In the mid 2010s, a sign of worldwide scientific progress is a nascent ability to begin to quantify an infinite constellation of stochastic cosmoses. This new December 2015 section will collect and report upon novel theoretical entries to consider other universes in the most part for parameters and propensities to contain living entities like us. We include some lengthy Abstracts for a sense of the expertise and technical vernacular.
Adams, Fred. Constraints on Alternative Universes: Stars and Habitable Planets with Different Fundamental Constants. arXiv:1511.06958. The University of Michigan astronomer and author has been a leader of these frontier journeys to distant cosmic spacescapes.
This paper develops constraints on the values of the fundamental constants that allow universes to be habitable. We focus on the fine structure constant α and the gravitational structure constant αG, and find the region in the α-αG plane that supports working stars and habitable planets. This work is motivated, in part, by the possibility that different versions of the laws of physics could be realized within other universes. The following constraints are enforced: [A] long-lived stable nuclear burning stars exist, [B] planetary surface temperatures are hot enough to support chemical reactions, [C] stellar lifetimes are long enough to allow biological evolution, [D] planets are massive enough to maintain atmospheres, [E] planets are small enough in mass to remain non-degenerate, [F] planets are massive enough to support sufficiently complex biospheres, [G] planets are smaller in mass than their host stars, and [H] stars are smaller in mass than their host galaxies. This paper delineates the portion of the α-αG plane that satisfies all of these constraints. The results indicate that viable universes --- with working stars and habitable planets --- can exist within a parameter space where the structure constants α and αG vary by several orders of magnitude. (Abstract)
Adams, Fred and Evan Grohs. On the Habitability of Universes without Stable Deuterium. Astroparticale Physics. 91/90, 2017. We added this new section to report entries like this which show how it has now become possible for human beings to contemplate entire cosmoses. Also posted at arXiv:1612.04741, here University of Michigan astrophysicists consider if a deficit of deuterium, one of two hydrogen isotopes, would affect an ability to form a modicum of living entities. Upon a natural philosophy reflection, incredulous to a Newton or Galileo, there must be some grand significance and purpose for our collaborative humankinder acumen to be able to quantify such multiUniVerse reaches.
In both stars and in the early universe, the production of deuterium is the first step on the way to producing heavier nuclei. If the strong force were slightly weaker, deuterium would not be stable, and many authors have noted that nuclesynthesis would be compromised so that helium production could not proceed through standard reaction chains. Motivated by the possibility that other regions of space-time could have different values for the fundamental constants, this paper considers stellar evolution in universes without stable deuterium and argues that such universes can remain habitable. With stars evolving through gravitational contraction, explosive nucleosynthesis, the triple-nucleon reaction, and the CNO cycle, universes with no stable deuterium are thus potentially habitable, contrary to many previous claims. (Abstract excerpts)
Adams, Fred and Evan Grohs. Stellar Helium Burning in Other Universes: A Solution to the Triple Alpha Fine-Tuning Problem. arXiv:1608.04690. Reviewed more in Anthropic Principle, a University of Michigan physicist and an astronomer enlist a new parameter by which a relative cosmic, life-bearing habitability can be quantified. See also by the authors On the Habitability of Universes without Stable Deuterium at 1612.04741.
Adams, Fred C.. The Degree of Fine-Tuning in our Universe – and Others. arXiv:1902.03928. In a 212 page paper to appear in Physics Reports, the collegial University of Michigan astrophysicist (search) enters a broad and deep mathematical survey to date of a stochastic infinity of exo-cosmoses. Its sections go from Particle Parameters, Cosmological Features, Dark Energy, Big Bang Nucleosynthesis, to Galactic Structures, Stellar Evolution, Solar Planets, and more. The main theme is the contingency of this temporally unfolding universe, and myriad vicarious others, with regard to how they might permit living, developmental systems. A conclusion is that while particle values are sharply tuned, astrophysical vistas allow a wider space (wiggle room). A general surmise so far is that our universe with sapient observers may be a better or maximal case. One might note that such witnesses apply J. A. Wheeler’s participatory model whence any extant cosmos requires an internal self-recognition to attain full existence. See also concurrent papers by McCullen Sandora herein.
Both fundamental constants that describe the laws of physics and cosmological parameters that determine the cosmic properties must fall within a range of values in order for the universe to develop astrophysical structures and support life. This paper reviews current constraints on these quantities. The standard model of particle physics contains both coupling constants and particle masses, and the allowed ranges of these parameters are discussed. We then consider cosmic parameters, including the total energy density, vacuum energy density, baryon-to-photon ratio, dark matter contribution, and the amplitude of primordial density fluctuations. These quantities are constrained by the requirements that the universe lives for a long time, emerges from the BBN epoch with an acceptable chemical composition, and can produce galaxies.
Adams, Fred, et al. Planets in Other Universes: Habitability Constraints on Density Fluctuations and Galactic Structure. arXiv:1505.06158. As a worldwide cerebral collaboration takes leave of our own cosmos, a University of Michigan team of astronomer Adams, physicist Katherine Coppess, and mathematician Anthony Bloch theorize generic modes of galaxy formation, structure, and habitable zones. A celestial propensity or inhibition to form stable, conducive planetary solar systems can then be entertained. It is noted that our home Earth, whereupon life has evolved to a worldwide sapience capable of such imaginations, might be an optimum biosphere, worthy of “superhabitable” status. This is an inaugural posting for this section, along with Constraints on Alternative Universes, Simulating the Universe(s), and On Separate Universes.
Motivated by the possibility that different versions of the laws of physics could be realized within other universes, this paper delineates the galactic parameters that allow for habitable planets and revisits constraints on the amplitude Q of the primordial density fluctuations. Previous work indicates that large values of Q lead to galaxies so dense that planetary orbits cannot survive long enough for life to develop. Small values of Q lead to delayed star formation, loosely bound galaxies, and compromised heavy element retention. This work generalizes previous treatments: [A] We consider models for the internal structure of galaxies and find the fraction of galactic real estate that allows stable, long-lived planetary orbits. [B] We perform a large ensemble of numerical simulations to estimate cross sections for the disruption of planetary orbits due to interactions with passing stars. [C] We consider disruption due to the background radiation fields produced by the galaxies. [D] One consequence of intense galactic background radiation fields is that some portion of the galaxy, denoted as the Galactic Habitable Zone, will provide the right flux levels to support habitable planets for essentially any planetary orbit. (Abstract)
Alonso-Serrano, Ana and Gil Jannes. Conceptual Challenges on the Road to the Multiverse. Universe. 5/10, 2019. MPI Gravitational Physics and Complutense University of Madrid astrophysicists provide an historic, philosophical, cosmological and anthropic survey of this expansive frontier
Alonso-Serrano, Ana, et al, eds. The Multiverse. Universe. July, 2019. Co-editors A A-S, MPI Gravitational Physics, Mariusz Dabrowski, University of Szczecin, Poland, and Thomas Naumann, Deutsches Elektronen-Synchrotron, Germany introduce a special place for studies about a relatively infinite scenario, some 400 years after Galileo’s moon, which is filled with all manner of spatial and temporal cosmoses. Among the entries are Multiverse – Too Much or Not Enough? by Michael Heller, Possible Origins and Properties of an Expanding, Dark Energy Providing a Dark Multiverse by Eckhard Rebhan, and four McCullen Sandora Papers (search) about factoring habitability estimates for our home planet and cosmos within this vast milieu. While still another (Copernican) devaluation is alluded to, in our worldwide organic genesis, human/Earth beings can be returned to a central significance.
The idea of the Multiverse, as a collection of possible universes, has entered the area of physics and cosmology for good. The term 'Multiverse' was first suggested by the philosopher William James in 1895 (see Historic Prescience). The diversity of possible physical shapes of a universe within the multiverse can be interpreted in terms of diversity of possible ways to choose physical parameters and can be related to the issue of varying physical constants and varying physical laws. One approach is superstring theory which led to an idea of superstring landscape or many ways to choose the vacua after the symmetry breaking. Anyway, one can consider the studies related to the concept of the Multiverse as a new revolution or paradigm in cosmology. It can be understood as the next step in the Copernican transit, where our habitat has lost relevance gradually as unique or special. The notion of the multiverse emerges naturally from some developments in cosmology and particle physics. (Issue Proposal excerpt)
Barnes, Luke, et al. Galaxy Formation Efficiency and the Multiverse Explanation of the Cosmological Constant with EAGLE Simulations. arXiv:1801.08781. A nine member Australian, British, and Dutch group including Geraint Lewis and Jaime Salcido can now proceed to quantify, and contemplate entire cosmoses by way of certain variable physical properties. Might we then wonder how special could our collective Earthly witness on an infinitesimal orb actually be, as we forthwith begin to consider an infinity of potentially viable cosmoses?
Models of the very early universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code from the EAGLE collaboration, we investigate the effect of the cosmological constant on the formation of galaxies and stars. We simulate universes with values of the cosmological constant ranging from Λ=0 to Λ0×300, where Λ0 is the value of the cosmological constant in our Universe. We use our simulations to predict the observed value of the cosmological constant, given a measure of the multiverse. (Abstract excerpt)
Barreira, Alexandre, et al. Separate Universe Simulations with IllustrisTNG. arXiv:1904.02070. MPI Astrophysics and Kavli Institute for the Physics and Mathematics of the Universe, Tokyo theorists study “baryonic effects on power spectrum responses and higher-order statistics.” This German-American cosmic quantification project (see quote) uses ground and telescope instrumentation along with computational visualizations. See also an earlier Separate Universe Simulations entry (Monthly Notices of the Royal Astronomical Society (448/L11, 2015) for more context.
The IllustrisTNG (TNG + the next generation) project is a suite of state-of-the-art cosmological galaxy formation simulations. Each simulation evolves a large swath of a mock Universe from soon after the Big-Bang until the present day while taking into account a wide range of physical processes that drive galaxy formation. The simulations can be used to study a broad range of topics surrounding how the Universe — and the galaxies within it — evolved over time. These components of the visible matter are organized in a 'Cosmic Web' of sheets, filaments, and voids, inside which the basic units of cosmic structure - galaxies - are embedded. To test our current ideas on the formation and evolution of galaxies, we strive to create simulated galaxies as detailed and realistic as possible, and compare them to galaxies observed in the real universe.
Barrow, John. The Book of Universes: Exploring the Limits of the Cosmos. New York: Norton, 2011. For a long time before the current proof of myriad planets, it was assumed that our bioworld Earth bioworld not be the only one. Since the 1980s, the same logic has led to a proposal of multiple cosmoses, first theoretically and now experimentally. A Cambridge University mathematician and author (search) surveys an infinite spatial and temporal spacescape from its origins to current vicarious infinities. We are thus treated to fractal, Swiss cheese, spinning, undulating, chaotic, magnetic, random, probable, self-creating universes. Again how fantastic is it that we infinitesimal beings can yet imagine and gain such cosmic knowledge?
Bouhmadi-Lopez, Mariam, et al. The Interacting Multiverse and its Effect on the Cosmic Microwave Background. arXiv:1809.09133. University of the Basque, University of Szczecin, Poland, and Ecological Station for Biocosmology, Spain move on to consider how whole cosmoses might intersect with each other in a way that might be amenable to theoretical study, along with their experimental detection. And it amazes that human beings can suddenly join on an infinitesimal bioworld to imagine and explore an entire dynamic multiverse.
We study a toy model of a multiverse consisting of canonically quantized universes that interact with each other on a quantum level based on a field-theoretical formulation of the Wheeler-DeWitt equation. This interaction leads to the appearance of a pre-inflationary phase in the evolution of the individual universes. We analyze scalar perturbations within the model and calculate the influence of the pre-inflationary phase onto the power spectrum of these perturbations. The result is that there is a suppression of power on large scales, which can describe well the Planck 2018 data for the cosmic microwave background anisotropies and could thus indicate a possible solution to the observed quadrupole discrepancy. (Abstract)
Boyle, Latham, et al. CPT-Symmetric Universe. Physical Review Letters. 1/251301, 2018. Perimeter Institute theoretical physicists LB, Kieran Finn, and director Neil Turok can now proceed to contemplate and quantify entire cosmoses with regard to variations if certain nuclear or energetic parameters were different. See also Quintessential Isocurvature in Separate Universe at arXiv:1409.6294 for another take. Within this website view, how fantastic is it that human beings altogether are able to learn about such vistas and imaginations. There must be some auspicious reason and purpose that we can do this.
We propose that the state of the universe does not spontaneously violate CPT (see below). Instead, the universe after the big bang is the CPT image of the universe before it, both classically and quantum mechanically. The pre- and post-bang epochs comprise a universe/anti-universe pair, emerging from nothing directly into a hot, radiation-dominated era. CPT symmetry selects a unique QFT vacuum state on such a spacetime, providing a new interpretation of the cosmological baryon asymmetry, as well as a remarkably economical explanation for the cosmological dark matter. Several other testable predictions follow: (i) the three light neutrinos are Majorana and allow neutrinoless double β decay; (ii) the lightest neutrino is massless; and (iii) there are no primordial long-wavelength gravitational waves. (Abstract excerpt)