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Most amino acids and sugars molecules occur in mirror, or chiral, images of each other, knowns as enantiomers. However, life on Earth is mostly homochiral: proteins contain almost exclusively L-amino acids, while only D-sugars appear in RNA and DNA. The mechanism behind this fundamental asymmetry of life remains unknown, despite much progress in the theoretical and experimental understanding of homochirality in the past decades. We review three potential mechanisms for the emergence of biological homochirality on primal Earth and explore their implications for astrobiology: the first, that biological homochirality is a stochastic process driven by local environmental fluctuations; the second, that it is driven by circularly-polarized ultraviolet radiation in star-forming regions; and the third, that it is driven by parity violation at the elementary particle level. We argue that each of these mechanisms leads to different observational consequences for the existence of enantiomeric excesses in our solar system and in exoplanets, pointing to the possibility that the search for life elsewhere will help elucidate the origins of homochirality on Earth., arXiv admin note: text overlap with arXiv:0802.1446

Every scientific endeavor begins with mystery. Scientists engage in their research for a variety of reasons-as diverse as their research interests are. But at the core, we find the same sense of awe and wonder that inspires spiritual ways to look at the world.

We introduce a new approach for cosmological parameter estimation based on the information-theoretical Jensen-Shannon divergence (${\cal D}_{\rm JS}$), calculating it for models in the restricted parameter space $\{H_0, w_0, w_a\}$, where $H_0$ is the value of the Hubble constant today, and $w_0$ and $w_a$ are dark energy parameters, with the other parameters held fixed at their best-fit values from the Planck 2018 data. As an application, we investigate the $H_0$ tension between the Planck temperature power spectrum data (TT) and the local astronomical data by comparing the $\Lambda$CDM model with the $w$CDM and the $w_0w_a$CDM dynamic dark energy models. We find agreement with other works using the standard Bayesian inference for parameter estimation; in addition, we show that while the ${\cal D}_{\rm JS}$ is equally minimized for both values of $H_0$ along the $(w_0,w_a)$ plane, the lines of degeneracy are different for each value of $H_0$. This allows for distinguishing between the two, once the value of either $w_0$ or $w_a$ is known., Comment: 5 pages, 3 figures. Final version accepted for publication in Physical Review D. Includes a new error analysis, a new figure, additional references, and a new author

We use an information-theoretic measure of shape complexity known as configurational entropy (CE) to investigate numerically the remarkably long lifetimes of spherically-symmetric ``resonant oscillons'' in three-dimensional and of azimuthally-symmetric oscillons in two-dimensional relativistic scalar field theories, which have been conjectured to be infinite. In 3d, we obtain a power law relating a stability measure derived from CE to the oscillons' lifetimes that, upon extrapolation to large times, offers support to this conjecture. In 2d, we obtain a three-way relation between the oscillons' energies, a CE-derived measure of their stability, and their radiation rates to support the conjecture that they asymptotically tend toward a classically-stable attractor solution., 9 pages, 9 figures

Einstein famously claimed that "the most incomprehensible thing about the universe is that it is comprehensible." This statement suggests that no amount of scientific explanation will suffice to make sense of the bizarre situation of the human mind within the universe. So what are the actual roles of awe and wonder within the framework of contemporary science? How, for instance, do awe and wonder inform scientists' understanding of the phenomena they are researching? What aspects of contemporary science are more likely to elicit wonder, and why? Is science rechanneling our innate thirst for knowledge and understanding toward more concrete and palpable realities, or is it aggravating the tension between truth and meaning by revealing the scope of our ignorance when it comes to probing the ultimate nature of reality? Physicist Marcelo Gleiser, experimental psychologist Tania Lombrozo, and physician Gavin Francis analyze the impact of awe and wonder on their own work and on the mindsets of their colleagues carrying out leading-edge scientific research.

We calculate the gravitational radiation background generated from boson star binaries formed in locally dense clusters with formation rate tracked by the regular star formation rate. We compute how the the frequency window in gravitational waves is affected by the boson field mass and repulsive self-coupling, anticipating constraints from EPTA and LISA. We also comment on the possible detectability of these binaries., 11 pages, 3 figures

We investigate the longevity of oscillons numerically, paying particular attention to radially-symmetric oscillons that have been conjectured to have an infinitely-long lifetime. In two spatial dimensions, oscillons have not been seen to decay. In three spatial dimensions, specific initial Gaussian configurations seem to lead to oscillons with spikes in lifetime that have been conjectured to be infinite. We study such ``resonant'' oscillons in two and three spatial dimensions, applying two tests to study their longevity: parametric resonance and virialization. Without offering a formal proof, our numerical results, within their precision, offer support for the conjecture that, in both dimensions, resonant oscillons may be infinitely long-lived., 15 pages, 14 figure. Version accepted for publication in Physical Review D. Two new figures, some comments added for clarification

We compute the configurational complexity (CC) for discrete soliton and rogue waves traveling along an Ablowitz-Ladik-Hirota (ALH) waveguide and modeled by a discrete nonlinear Schrodinger equation. We show that for a specific range of the soliton transverse direction κ propagating along the parametric time ζ ( t ) , CC reaches an evolving series of global minima. These minima represent maximum compressibility of information in the momentum modes along the Ablowitz-Ladik-Hirota waveguide. Computing the CC for rogue waves as a function of background amplitude modulation μ, we show that it displays two essential features: a maximum representing the optimal value for the rogue wave inception (the “gradient catastrophe”) and saturation representing the rogue wave dispersion into constituent wave modes. We show that saturation is achieved earlier for higher values of modulation amplitude as the discrete rogue wave evolves along time ζ ( t ) .

We extend the use of configurational information measures (CIMs) to instantons and vacuum decay in arbitrary spatial dimensions. We find that both the complexity and the information content in the shape of instanton solutions have distinct regions of behavior in parameter space, discriminating between qualitative thin- and thick-wall profiles. For Euclidean spaces of dimension D, we show that for D≥6 instantons undergo a qualitative change of behavior from their lower-dimensional counterparts, indicating that D=6 is a critical dimension. We also find a scaling law relating the different CIMs to the rate of vacuum decay, thus connecting the stability of the vacuum to the informational complexity stored in the shape of the related critical bounce.

Oscillons are long-lived, spherically symmetric, attractor scalar field configurations that emerge as certain field configurations evolve in time. It has been known for many years that there is a direct correlation between the initial configuration’s shape and the resulting oscillon lifetime: a shape memory. In this paper, we use an information-entropic measure of spatial complexity known as differential configurational entropy (DCE) to obtain estimates of oscillon lifetimes in scalar field theories with symmetric and asymmetric double-well potentials. The time-dependent DCE is built from the Fourier transform of the two-point correlation function of the energy density of the scalar field configuration. We obtain a scaling law correlating oscillon lifetimes and measures obtained from its evolving DCE. For the symmetric double well, for example, we show that we can apply DCE to predict an oscillon’s lifetime with an average accuracy of 6% or better. We also show that the DCE acts as a pattern discriminator, able to distinguish initial configurations that evolve into long-lived oscillons from other nonperturbative short-lived fluctuations.

The essence of physical reality-what the world consists of-has been a heated focus of contention for millennia. First with philosophers and then with physicists, the debate has been polarized since the beginning: while those loosely known as Platonists search for an underlying unity in nature, others caution that such unity is unachievable in practice and in principle. In this essay, we review both positions, arguing strongly for the latter in anticipation of experimental results from the Large Hadron Collider, the particle accelerator from the European Center for Nuclear Research. We further argue that, for the first time in history, the material essence of reality could be determined from an empirical standpoint as opposed to a purely dialectic one, settling the age-old debate.

The holy grail of physics has been to merge each of its fundamental branches into a unified "theory of everything" that would explain the functioning and existence of the universe. The last step toward this goal is to reconcile general relativity with the principles of quantum mechanics, a quest that has thus far eluded physicists. Will physics ever be able to develop an all-encompassing theory, or should we simply acknowledge that science will always have inherent limitations as to what can be known? Should new theories be validated solely on the basis of calculations that can never be empirically tested? Can we ever truly grasp the implications of modern physics when the basic laws of nature do not always operate according to our standard paradigms? These and other questions are discussed in this paper.

We show that a newly proposed Shannon-like entropic measure of shape complexity applicable to spatially-localized or periodic mathematical functions known as configurational entropy (CE) can be used as a predictor of spontaneous decay rates for one-electron atoms. The CE is constructed from the Fourier transform of the atomic probability density. For the hydrogen atom with degenerate states labeled with the principal quantum number n, we obtain a scaling law relating the n-averaged decay rates to the respective CE. The scaling law allows us to predict the n-averaged decay rate without relying on the traditional computation of dipole matrix elements. We tested the predictive power of our approach up to n=20, obtaining an accuracy better than 3.7% within our numerical precision, as compared to spontaneous decay tables listed in the literature., Comment: 19 pages, 3 figures

The reach of the scientific method is constrained by the limitations of our tools and the intrinsic impenetrability of some of nature’s deepest questions. The reach of the scientific method is constrained by the limitations of our tools and the intrinsic impenetrability of some of nature’s deepest questions.

Spatially-bound objects across diverse length and energy scales are characterized by a binding energy. We propose that their spatial structure is mathematically encoded as information in their momentum modes and described by a measure known as configurational entropy (CE). Investigating solitonic Q-balls and stars with a polytropic equation of state $P = K{\rho}^{\gamma}$, we show that objects with large binding energy have low CE, whereas those at the brink of instability (zero binding energy) have near maximal CE. In particular, we use the CE to find the critical charge allowing for classically stable Q-balls and the Chandrasekhar limit for white dwarfs $({\gamma} = 4/3)$ with an accuracy of a few percent., Comment: 4 figures

A key open question in the study of life is the origin of biomolecular homochirality: almost every life-form on Earth has exclusively levorotary amino acids and dextrorotary sugars. Will the same handedness be preferred if life is found elsewhere? We review some of the pertinent literature and discuss recent results suggesting that life's homochirality resulted from sequential chiral symmetry breaking triggered by environmental events. In one scenario, autocatalytic prebiotic reactions undergo stochastic fluctuations due to environmental disturbances. In another, chiral-selective polymerization reaction rates influenced by environmental effects lead to substantial chiral excess even in the absence of autocatalysis. Applying these arguments to other potentially life-bearing platforms has implications to the search for extraterrestrial life: we predict that a statistically representative sampling of extraterrestrial stereochemistry will be racemic (chirally neutral) on average., 12 pages, 7 figures. Plenary talk delivered at the S\~ao Paulo Advanced School of Astrobiology, S\~ao Paulo, December 2011. In press, Int. J. Astrobio. Added small clarification in conclusion section

The history of life on Earth and in other potential life-bearing planetary platforms is deeply linked to the history of the universe. Since life as we know it relies on chemical elements forged in dying heavy stars, the universe needs to be old enough for stars to form and evolve. Current cosmological theory indicates that the universe is 13.7$\pm 0.13$ billion years old and that the first stars formed hundreds of millions of years after the big bang. At least some stars formed with stable planetary systems wherein a set of biochemical reactions leading to life could have taken place. In this lecture, I argue that we can divide cosmological history into four ages, from the big bang to intelligent life. The Physical Age describes the origin of the universe, of matter, of cosmic nucleosynthesis, as well as the formation of the first stars and galaxies. The Chemical Age begun when heavy stars provided the raw ingredients for life through stellar nucleosynthesis and describes how heavier chemical elements collected in nascent planets and moons to give rise to prebiotic biomolecules. The Biological Age describes the origin of early life, its evolution through Darwinian natural selection, and the emergence of complex multicellular life forms. Finally, the Cognitive Age describes how complex life evolved into intelligent life capable of self-awareness and of developing technology through the directed manipulation of energy and materials. We conclude discussing whether we are the rule or the exception., 7 pages, Opening plenary talk delivered at the S\~ao Paulo Advanced School of Astrobiology, S\~ao Paulo, December 2011. In press, Int. J. Astrobio. Reference updated

We investigate the possibility that prebiotic homochirality can be achieved exclusively through chiral-selective reaction rate parameters without any other explicit mechanism for chiral bias. Specifically, we examine an open network of polymerization reactions, where the reaction rates can have chiral-selective values. The reactions are neither autocatalytic nor do they contain explicit enantiomeric cross-inhibition terms. We are thus investigating how rare a set of chiral-selective reaction rates needs to be in order to generate a reasonable amount of chiral bias. We quantify our results adopting a statistical approach: varying both the mean value and the rms dispersion of the relevant reaction rates, we show that moderate to high levels of chiral excess can be achieved with fairly small chiral bias, below 10%. Considering the various unknowns related to prebiotic chemical networks in early Earth and the dependence of reaction rates to environmental properties such as temperature and pressure variations, we argue that homochirality could have been achieved from moderate amounts of chiral selectivity in the reaction rates., 15 pages, 6 figures, accepted for publication in Origins of Life and Evolution of Biospheres

The activation-polymerization-epimerization-depolymerization (APED) model of Plasson et al. has recently been proposed as a mechanism for the evolution of homochirality on prebiotic Earth. The dynamics of the APED model in two-dimensional spatially-extended systems is investigated for various realistic reaction parameters. It is found that the APED system allows for the formation of isolated homochiral proto-domains surrounded by a racemate. A diffusive slowdown of the APED network such as induced through tidal motion or evaporating pools and lagoons leads to the stabilization of homochiral bounded structures as expected in the first self-assembled protocells., 10 pages, 5 figures

We use a novel measure of shape complexity known as configurational entropy to obtain stability bounds of various astrophysical objects. We apply the method to Newtonian polytropes, neutron stars with an Oppenheimer-Volkoff equation of state, and to self-gravitating configurations of complex scalar field (boson star) in ground and excited states. The versatility of this method has also been tested on hydrogen atom in comparison with boson stars. Configurational entropic measure locates critical stability regions obtained from perturbation method with accuracy of a few percent or better.

The holy grail of physics has been to merge each of its fundamental branches into a unified "theory of everything" that would explain the functioning and existence of the universe. The last step toward this goal is to reconcile general relativity with the principles of quantum mechanics, a quest that has thus far eluded physicists. Will physics ever be able to develop an all-encompassing theory, or should we simply acknowledge that science will always have inherent limitations as to what can be known? Should new theories be validated solely on the basis of calculations that can never be empirically tested? Can we ever truly grasp the implications of modern physics when the basic laws of nature do not always operate according to our standard paradigms? These and other questions are discussed in this paper.

We present a closed bouncing universe model where the value of coupling constants is set by the dynamics of a ghost-like dilatonic scalar field. We show that adding a periodic potential for the scalar field leads to a cyclic Friedmann universe where the values of the couplings vary randomly from one cycle to the next. While the shuffling of values for the couplings happens during the bounce, within each cycle their time-dependence remains safely within present observational bounds for physically-motivated values of the model parameters. Our model presents an alternative to solutions of the fine tuning problem based on string landscape scenarios., 5 pages, 2 figures

We obtain bounds on the stability of various self-gravitating astrophysical objects using a new measure of shape complexity known as configurational entropy. We apply the method to Newtonian polytropes, neutron stars with an Oppenheimer-Volkoff equation of state, and to self-gravitating configurations of complex scalar field (boson stars) with different self-couplings, showing that the critical stability region of these stellar configurations obtained from traditional perturbation methods correlates well with critical points of the configurational entropy with accuracy of a few percent or better., 10 pages, 12 figures