Quark Masses: An Environmental Impact Statement
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In this article, the authors investigate worlds that lie on a slice through the parameter space of the standard model over which quark masses vary, and identify the region in quark mass space where nuclei would be made from three or more baryon species.Abstract:
We investigate worlds that lie on a slice through the parameter space of the standard model over which quark masses vary. We allow as many as three quarks to participate in nuclei, while fixing the mass of the electron and the average mass of the lightest baryon flavor multiplet. We classify as congenial worlds that satisfy the environmental constraint that the quark masses allow for stable nuclei with charge one, six, and eight, making organic chemistry possible. Whether a congenial world actually produces observers capable of measuring those quark masses depends on a multitude of historical contingencies, beginning with primordial nucleosynthesis and including other astrophysical processes, which we do not explore. Such constraints may be independently superimposed on our results. Environmental constraints such as the ones we study may be combined with information about the a priori distribution of quark masses over the landscape of possible universes to determine whether the measured values of the quark masses are determined environmentally, but our analysis is independent of such an anthropic approach. We estimate baryon masses as functions of quark masses via first-order perturbation theory in flavor SU(3) breaking. We estimate nuclear masses as functions of the baryon masses using two separatemore » tools: for a nucleus made of two baryon species, when possible we consider its analog in our world, a nucleus with a similar binding energy, up to Coulomb contributions. For heavy nuclei or nuclei made of more than two baryons, we develop a generalized Weizsaecker semiempirical mass formula, in which strong kinematic flavor symmetry violation is modeled by a degenerate Fermi gas . We check for the stability of nuclei against fission, strong particle emission (analogous to {alpha} decay), and weak nucleon emission. For two light quarks with charges 2/3 and -1/3 , we find a band of congeniality roughly 29 MeV wide in their mass difference, with our own world lying comfortably away from the edges. We also find another, less robust region of congeniality with one light, charge -1/3 quark, and two heavier, approximately degenerate quarks with charges -1/3 and 2/3. No other assignment of light quark charges yields congenial worlds with two baryons participating in nuclei. We identify the region in quark mass space where nuclei would be made from three or more baryon species. We discuss issues relevant to the congeniality of such worlds, but a full characterization of them is left for future investigation.« lessread more
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References
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Measurements of Omega and Lambda from 42 High-Redshift Supernovae
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TL;DR: In this paper, the mass density, Omega_M, and cosmological-constant energy density of the universe were measured using the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology project.
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Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
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TL;DR: In this article, the authors used spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 " z " 0.62.
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Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant
Adam G. Riess,Alexei V. Filippenko,Peter Challis,Alejandro Clocchiattia,Alan H. Diercks,Peter M. Garnavich,R. L. Gilliland,Craig J. Hogan,Saurabh Jha,Robert P. Kirshner,Bruno Leibundgut,Mark M. Phillips,David J Reiss,Brian P. Schmidt,Robert A. Schommer,R. Chris Smith,Jason Spyromilio,Christopher W. Stubbs,Nicholas B. Suntzeff,John L. Tonry +19 more
TL;DR: In this paper, the authors present observations of 10 type Ia supernovae (SNe Ia) between 0.16 0 and 4.0 sigma confidence levels, for two fitting methods respectively.
Journal ArticleDOI
Measurements of Omega and Lambda from 42 High-Redshift Supernovae
Saul Perlmutter,Greg Aldering,G. Goldhaber,R. A. Knop,Peter Nugent,P. G. Castro,Susana E. Deustua,Sebastien Fabbro,A. Goobar,D. E. Groom,I. M. Hook,A. G. Kim,M. Y. Kim,Julia C. Lee,Nelson J. Nunes,Reynald Pain,C. R. Pennypacker,R. M. Quimby,C. Lidman,Richard S. Ellis,Michael G. Irwin,Richard G. McMahon,P. Ruiz-Lapuente,Nicholas A. Walton,Bradley E. Schaefer,B. J. Boyle,Alexei V. Filippenko,Thomas Matheson,A. S. Fruchter,Nino Panagia,Heidi Jo Newberg,W. J. Couch +31 more
TL;DR: In this paper, the mass density, Omega_M, and cosmological-constant energy density of the universe were measured by the analysis of 42 Type Ia supernovae discovered by the Supernova Cosmology Project.
Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant To Appear in the Astronomical Journal
Adam G. Riess,Alexei V. Filippenko,Peter Challis,A. Clocchiatti,Alan H. Diercks,R. L. Gilliland,Craig J. Hogan,Saurabh Jha,Robert P. Kirshner,Bruno Leibundgut,David J Reiss,Brian P. Schmidt,Robert A. Schommer,R. Chris Smith,Jason Spyromilio,Christopher W. Stubbs,Nicholas B. Suntzeff,John L. Tonry +17 more
TL;DR: The spectral and photometric observations of 10 type Ia supernovae (SNe Ia) in the redshift range 0.16 � z � 0.62 were presented in this paper.