Kooperativer Bibliotheksverbund

Berlin Brandenburg

and
and

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Astrophysics
Type of Medium
Language
Year
  • 1
    Language: English
    In: Physical review letters, 10 January 2014, Vol.112(1), pp.011302
    Description: Multifield models of inflation with nonminimal couplings are in excellent agreement with the recent results from Planck. Across a broad range of couplings and initial conditions, such models evolve along an effectively single-field attractor solution and predict values of the primordial spectral index and its running, the tensor-to-scalar ratio, and non-Gaussianities squarely in the observationally most-favored region. Such models can also amplify isocurvature perturbations, which could account for the low power recently observed in the cosmic microwave background power spectrum at low multipoles. Future measurements of primordial isocurvature perturbations could distinguish between the currently viable possibilities.
    Keywords: Astrophysics - Cosmology And Extragalactic Astrophysics;
    ISSN: 00319007
    E-ISSN: 1079-7114
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Language: English
    In: Science, 11 February 2005, Vol.307(5711), pp.884-890
    Description: Understanding the behavior of the universe at large depends critically on insights about the smallest units of matter and their fundamental interactions. Inflationary cosmology is a highly successful framework for exploring these interconnections between particle physics and gravitation. Inflation makes several predictions about the present state of the universe-such as its overall shape, large-scale smoothness, and smaller scale structure-which are being tested to unprecedented accuracy by a new generation of astronomical measurements. The agreement between these predictions and the latest observations is extremely promising. Meanwhile, physicists are busy trying to understand inflation's ultimate implications for the nature of matter, energy, and spacetime.
    Keywords: Physical sciences -- Astronomy -- Astronomical cosmology ; Physical sciences -- Physics -- Astronomical cosmology ; Physical sciences -- Astronomy -- Astronomical cosmology ; Physical sciences -- Astronomy -- Energy ; Physical sciences -- Physics -- Mathematical physics ; Physical sciences -- Physics -- Linear algebra ; Mathematics -- Pure mathematics -- Fundamental forces ; Physical sciences -- Physics -- Matter ; Physical sciences -- Physics -- Astrophysics ; Physical sciences -- Astronomy -- Astrophysics
    ISSN: 00368075
    E-ISSN: 10959203
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Description: Models of cosmic inflation suggest that our universe underwent an early phase of accelerated expansion, driven by the dynamics of one or more scalar fields. Inflationary models make specific, quantitative predictions for several observable quantities, including particular patterns of temperature anistropies in the cosmic microwave background radiation. Realistic models of high-energy physics include many scalar fields at high energies. Moreover, we may expect these fields to have nonminimal couplings to the spacetime curvature. Such couplings are quite generic, arising as renormalization counterterms when quantizing scalar fields in curved spacetime. In this chapter I review recent research on a general class of multifield inflationary models with nonminimal couplings. Models in this class exhibit a strong attractor behavior: across a wide range of couplings and initial conditions, the fields evolve along a single-field trajectory for most of inflation. Across large regions of phase space and parameter space, therefore, models in this general class yield robust predictions for observable quantities that fall squarely within the "sweet spot" of recent observations. Comment: 17pp, 2 figs. References added to match the published version. Published in {\it At the Frontier of Spacetime: Scalar-Tensor Theory, Bell's Inequality, Mach's Principle, Exotic Smoothness}, ed. T. Asselmeyer-Maluga (Springer, 2016), pp. 41-57, in honor of Carl Brans's 80th birthday
    Keywords: Astrophysics - Cosmology And Nongalactic Astrophysics ; General Relativity And Quantum Cosmology
    Source: Cornell University
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Language: English
    In: Physical Review. D, Particles Fields, 15 April 2010, Vol.81(8)
    Description: Many interesting models incorporate scalar fields with nonminimal couplings to the spacetime Ricci curvature scalar. As is well known, if only one scalar field is nonminimally coupled, then one may perform a conformal transformation to a new frame in which both the gravitational portion of the Lagrangian and the kinetic term for the (rescaled) field assume canonical form. We examine under what conditions the gravitational and kinetic terms in the Lagrangian may be brought into canonical form when more than one scalar field has nonminimal coupling. A particular class of two-field models admits such a transformation, but models with more than two nonminimally coupled fields, in general, do not.
    Keywords: Physics Of Elementary Particles And Fields ; Coupling ; Lagrangian Function ; Scalar Fields ; Simulation ; Space-Time ; Transformations ; Functions ; Physics
    ISSN: 0556-2821
    ISSN: 15507998
    E-ISSN: 1089-4918
    E-ISSN: 15502368
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Language: English
    In: Physical Review D, 01 September 2018, Vol.98(6)
    Description: Not provided.
    Keywords: Astronomy & Astrophysics ; Physics ; Astronomy & Astrophysics ; Physics
    ISSN: 2470-0010
    E-ISSN: 2470-0029
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Language: English
    In: Physical review letters, 10 February 2017, Vol.118(6), pp.060401
    Description: Bell's theorem states that some predictions of quantum mechanics cannot be reproduced by a local-realist theory. That conflict is expressed by Bell's inequality, which is usually derived under the assumption that there are no statistical correlations between the choices of measurement settings and anything else that can causally affect the measurement outcomes. In previous experiments, this "freedom of choice" was addressed by ensuring that selection of measurement settings via conventional "quantum random number generators" was spacelike separated from the entangled particle creation. This, however, left open the possibility that an unknown cause affected both the setting choices and measurement outcomes as recently as mere microseconds before each experimental trial. Here we report on a new experimental test of Bell's inequality that, for the first time, uses distant astronomical sources as "cosmic setting generators." In our tests with polarization-entangled photons, measurement settings were chosen using real-time observations of Milky Way stars while simultaneously ensuring locality. Assuming fair sampling for all detected photons, and that each stellar photon's color was set at emission, we observe statistically significant ≳7.31σ and ≳11.93σ violations of Bell's inequality with estimated p values of ≲1.8×10^{-13} and ≲4.0×10^{-33}, respectively, thereby pushing back by ∼600  years the most recent time by which any local-realist influences could have engineered the observed Bell violation.
    Keywords: Quantum Physics ; Astrophysics - Cosmology And Nongalactic Astrophysics;
    ISSN: 00319007
    E-ISSN: 1079-7114
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Language: English
    In: Physical Review. D, Particles Fields, 15 June 2010, Vol.81(12)
    Description: Realistic models of particle physics include many scalar fields. These fields generically have nonminimal couplings to the Ricci curvature scalar, either as part of a generalized Einstein theory or as necessary counterterms for renormalization in curved background spacetimes. We develop a gauge-invariant formalism for calculating primordial perturbations in models with multiple nonminimally coupled fields. We work in the Jordan frame (in which the nonminimal couplings remain explicit) and identify two distinct sources of entropy perturbations for such models. One set of entropy perturbations arises from interactions among the multiple fields. The second set arises from the presence of nonminimal couplings. Neither of these varieties of entropy perturbations will necessarily be suppressed in the long-wavelength limit, and hence they can amplify the curvature perturbation {zeta}, even for modes that have crossed outside the Hubble radius. Models that overproduce long-wavelength entropy perturbations endanger the close fit between predicted inflationary spectra and empirical observations.
    Keywords: Physics Of Elementary Particles And Fields ; Astrophysics, Cosmology And Astronomy ; Coupling ; Disturbances ; Entropy ; Gauge Invariance ; Hubble Effect ; Inflationary Universe ; Interactions ; Perturbation Theory ; Renormalization ; Scalar Fields ; Space-Time ; Spectra ; Wavelengths ; Cosmological Models ; Invariance Principles ; Mathematical Models ; Physical Properties ; Thermodynamic Properties ; Physics
    ISSN: 0556-2821
    E-ISSN: 1089-4918
    E-ISSN: 15502368
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    Language: English
    In: Physical Review D, 05 March 2013, Vol.87(6)
    Description: Realistic models of high-energy physics include multiple scalar fields. Renormalization requires that the fields have nonminimal couplings to the spacetime Ricci curvature scalar, and the couplings can be large at the energy scales of early-universe inflation. The nonminimal couplings induce a nontrivial field-space manifold in the Einstein frame, and they also yield an effective potential in the Einstein frame with nontrivial curvature. The ridges or bumps in the Einstein-frame potential can lead to primordial non-Gaussianities of observable magnitude. We develop a covariant formalism to study perturbations in such models and calculate the primordial bispectrum. As in previous studies of non-Gaussianities in multifield models, our results for the bispectrum depend sensitively on the fields' initial conditions. Comment: 41 pages, 11 figures. Minor changes and references added to match published version
    Keywords: Physics
    ISSN: 1550-7998
    E-ISSN: 1550-2368
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Language: English
    In: Physical Review D, 3/2014, Vol.89(6)
    Description: Recent measurements by the {\it Planck} experiment of the power spectrum of temperature anisotropies in the cosmic microwave background radiation (CMB) reveal a deficit of power in low multipoles compared to the predictions from best-fit $\Lambda$CDM cosmology. The low-$\ell$ anomaly may be explained by the presence of primordial isocurvature perturbations in addition to the usual adiabatic spectrum, and hence may provide the first robust evidence that early-universe inflation involved more than one scalar field. In this paper we explore the production of isocurvature perturbations in nonminimally coupled two-field inflation. We find that this class of models readily produces enough power in the isocurvature modes to account for the \emph{Planck} low-$\ell$ anomaly, while also providing excellent agreement with the other {\it Planck} results. Comment: 19 pages, 15 figures. Minor edits to match published version
    Keywords: Astrophysics - Cosmology And Nongalactic Astrophysics;
    ISSN: 1550-7998
    E-ISSN: 1550-2368
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Language: English
    In: Physics Letters B, 02 June 2014, Vol.733, pp.112-119
    Description: Models of cosmic inflation posit an early phase of accelerated expansion of the universe, driven by the dynamics of one or more scalar fields in curved spacetime. Though detailed assumptions about fields and couplings vary across models, inflation makes specific, quantitative predictions for several observable quantities, such as the flatness parameter ( ) and the spectral tilt of primordial curvature perturbations ( ), among others—predictions that match the latest observations from the satellite to very good precision. In the light of data from as well as recent theoretical developments in the study of eternal inflation and the multiverse, we address recent criticisms of inflation by Ijjas, Steinhardt, and Loeb. We argue that their conclusions rest on several problematic assumptions, and we conclude that cosmic inflation is on a stronger footing than ever before.
    Keywords: Physics
    ISSN: 0370-2693
    E-ISSN: 1873-2445
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. Further information can be found on the KOBV privacy pages