Nuclear astrophysics of worlds in the string landscape

Hogan, Craig J.

doi:10.1103/physrevd.74.123514

Cited by 45 publications

(101 citation statements)

References 45 publications

(76 reference statements)

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“…In particular, values of p > 0:1 become more accessible. Our results for current pulsar timing experiments are substantially less constraining than the estimates of Hogan [14], which relied on a less conservative pulsar timing bound [24], and did not include effects of late-time acceleration. Currently, the pulsar limit is the most constraining, but Advanced LIGO, LISA, and future pulsar timing experiments are expected to explore all of this parameter space.…”

Section: 111101 (2007) P H Y S I C a L R E V I E W L E T T E R S mentioning

confidence: 77%

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Gravitational-Wave Stochastic Background from Cosmic Strings

2007

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We consider the stochastic background of gravitational waves produced by a network of cosmic strings and assess their accessibility to current and planned gravitational wave detectors, as well as to big bang nucleosynthesis (BBN), cosmic microwave background (CMB), and pulsar timing constraints. We find that current data from interferometric gravitational wave detectors, such as Laser Interferometer Gravitational Wave Observatory (LIGO), are sensitive to areas of parameter space of cosmic string models complementary to those accessible to pulsar, BBN, and CMB bounds. Future more sensitive LIGO runs and interferometers such as Advanced LIGO and Laser Interferometer Space Antenna (LISA) will be able to explore substantial parts of the parameter space.

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Section: 111101 (2007) P H Y S I C a L R E V I E W L E T T E R S mentioning

confidence: 77%

“…The latter generalization allows us to compute the background when string loops are large when they are formed and thus long lived, a possibility suggested by recent numerical simulations [12,13]. Recently, Hogan [14] has made analytic estimates for the case when the size of loops at formation is about a tenth of the horizon.…”

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confidence: 99%

Gravitational-Wave Stochastic Background from Cosmic Strings

2007

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“…(18). This boundary corresponds to the stability of a deuteron under strong interactions, which requires…”

Section: Stability Boundaries For Neutrons Deuterons and Complex Nucleimentioning

confidence: 99%

“…Such a neutron-stable world would not have dense astrophysical objects fueled by nuclear energy release, such as main-sequence stars in our universe [18]. Another example of violent boundaries is that of vanishing deuteron binding energy…”

Section: The Relevant Complex Structuresmentioning

confidence: 99%

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Evidence for the multiverse in the standard model and beyond

Hall

Nomura

2008

Phys. Rev. D

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In any theory it is unnatural if the observed values of parameters lie very close to special values that determine the existence of complex structures necessary for observers. A naturalness probability, P , is introduced to numerically evaluate the degree of unnaturalness. If P is very small in all known theories, corresponding to a high degree of fine-tuning, then there is an observer naturalness problem. In addition to the well-known case of the cosmological constant, we argue that nuclear stability and electroweak symmetry breaking represent significant observer naturalness problems. The naturalness probability associated with nuclear stability depends on the theory of flavor, but for all known theories is conservatively estimated as P nuc < ∼ (10 −3 -10 −2 ), and for simple theories of electroweak symmetry breaking P EWSB < ∼ (10 −2 -10 −1 ). This pattern of unnaturalness in three different arenas, cosmology, nuclear physics, and electroweak symmetry breaking, provides evidence for the multiverse, since each problem may be easily solved by environmental selection. In the nuclear case the problem is largely solved even if the multiverse distribution for the relevant parameters is relatively flat. With somewhat strongly varying distributions, it is possible to understand both the close proximity to neutron stability and the values of m e and m d − m u in terms of the electromagnetic mass difference between the proton and neutron, δ EM ≃ 1 ± 0.5 MeV. It is reasonable that multiverse distributions are strong functions of Lagrangian parameters, since they depend not only on the landscape of vacua, but also on the population mechanism, "integrating out" other parameters, and on a density of observers factor. In any theory with mass scale M that is the origin of electroweak symmetry breaking, strongly varying multiverse distributions typically lead either to a little hierarchy, v/M ≈ (10 −2 -10 −1 ), or to a large hierarchy, v ≪ M . In certain multiverses, where electroweak symmetry breaking occurs only if M is below some critical value, we find that a little hierarchy develops with the value of v 2 /M 2 suppressed by an extra loop factor, as well as by the strength of the distribution. Since the correct theory of electroweak symmetry breaking is unknown, our estimate for P EWSB is theoretical. The LHC will lead to a much more robust determination of P EWSB , and, depending on which theory is indicated by the data, the observer naturalness problem of electroweak symmetry breaking may be removed or strengthened. For each of the three arenas, the discovery of a natural theory would eliminate the evidence for the multiverse; but in the absence of such a theory, the multiverse provides a provisional understanding of the data.

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Formation & evolution of cosmic superstrings: a short review

Sakellariadou

2010

Fortschritte der Physik

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Nuclear astrophysics of worlds in the string landscape

Cited by 45 publications

References 45 publications

Gravitational-Wave Stochastic Background from Cosmic Strings

Gravitational-Wave Stochastic Background from Cosmic Strings

Evidence for the multiverse in the standard model and beyond

Formation & evolution of cosmic superstrings: a short review

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