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  • 1
    Book
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    L' altra faccia dell'universo : i segreti della materia e dell'energia oscura (2018)
    Bologna : Il Mulino
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    UID:
    (DE-602)gbv_1030786496
    Format: 167 Seiten, 4 ungezählte Blätter , Illustrationen , 21 cm
    ISBN: 9788815279514
    Series Statement: Intersezioni 510
    Note: L. Amendola teaches at the University of Heidelberg
    Language: Italian
    Keywords: Dunkle Materie ; Dunkle Energie
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  • 2
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    Variation of fundamental parameters and dark energy : a principal component approach (2012)
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    UID:
    (DE-627)1565258479
    Format: 10
    Content: We discuss methods based on Principal Component Analysis to constrain the dark energy equation of state using a combination of Type Ia supernovae at low redshift and spectroscopic measurements of varying fundamental couplings at higher redshifts. We discuss the performance of this method when future better-quality datasets are available, focusing on two forthcoming ESO spectrographs - ESPRESSO for the VLT and CODEX for the E-ELT - which include these measurements as a key part of their science cases. These can realize the prospect of a detailed characterization of dark energy properties almost all the way up to redshift 4.
    Note: Gesehen am 13.11.2017
    In: De.arxiv.org, [Erscheinungsort nicht ermittelbar] : Arxiv.org, 1991, (2012) Artikel-Nummer 1109.6793, 10 Seiten
    In: year:2012
    In: extent:10
    Language: English
    URL: Volltext  (kostenfrei)
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  • 3
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    Measuring our peculiar velocity on the CMB with high-multipole off-diagonal correlations (2011)
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    UID:
    (DE-627)1565264452
    Format: 20
    Content: Our peculiar velocity with respect to the CMB rest frame is known to induce a large dipole in the CMB. However, the motion of an observer has also the effect of distorting the anisotropies at all scales, as shown by Challinor and Van Leeuwen (2002), due to aberration and Doppler effects. We propose to measure independently our local motion by using off-diagonal two-point correlation functions for high multipoles. We study the observability of the signal for temperature and polarization anisotropies. We point out that Planck can measure the velocity $\beta$ with an error of about 30% and the direction with an error of about 20 degrees. This method constitutes a cross-check, which can be useful to verify that our CMB dipole is due mainly to our velocity or to disentangle the velocity from other possible intrinsic sources. Although in this paper we focus on our peculiar velocity, a similar effect would result also from other intrinsic vectorial distortion of the CMB which would induce a dipolar lensing. Measuring the off-diagonal correlation terms is therefore a test for a preferred direction on the CMB sky.
    Note: Gesehen am 13.11.2017
    In: De.arxiv.org, [Erscheinungsort nicht ermittelbar] : Arxiv.org, 1991, (2011) Artikel-Nummer 1008.1183, 20 Seiten
    In: year:2011
    In: extent:20
    Language: English
    URL: Volltext  (kostenfrei)
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  • 4
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    Is it possible to observationally distinguish adiabatic quartessence from [lambda]CDM ? (2006)
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    UID:
    (DE-627)1565372123
    Format: 5
    Content: The equation of state (EOS) in quartessence models interpolates between two stages:
    Note: Im Titel ist das Lambda als griechischer Buchstabe dargestellt , Gesehen am 15.11.2017
    In: De.arxiv.org, [Erscheinungsort nicht ermittelbar] : Arxiv.org, 1991, (2006) Artikel-Nummer 0604013, 5 Seiten
    In: year:2006
    In: extent:5
    Language: English
    URL: Volltext  (kostenfrei)
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  • 5
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    Phantom energy mediates a long-range repulsive force (2004)
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    UID:
    (DE-627)1565420128
    Format: 4
    Content: Scalar field models with non-standard kinetic terms have been proposed in the context of k-inflation, of Born-Infeld lagrangians, of phantom energy and, more in general, of low-energy string theory. In general, scalar fields are expected to couple to matter inducing a new interaction. In this paper I derive the cosmological perturbation equations and the Yukawa correction to gravity for such general models. I find three interesting results: first, when the field behaves as phantom energy (equation of state less than -1) then the coupling strength is negative, inducing a long-range repulsive force; second, the dark energy field might cluster on astrophysical scales; third, applying the formalism to a Brans-Dicke theory with general kinetic term it is shown that its Newtonian effects depend on a single parameter that generalizes the Brans-Dicke constant.
    Note: Gesehen am 16.11.2017
    In: De.arxiv.org, [Erscheinungsort nicht ermittelbar] : Arxiv.org, 1991, (2005) Artikel-Nummer 0506222, 4 Seiten
    In: year:2005
    In: extent:4
    Language: English
    URL: Volltext  (kostenfrei)
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  • 6
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    Cosmic microwave background as a gravity probe (2003)
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    UID:
    (DE-627)1565450949
    Format: 4
    ISSN: 2041-8213
    Content: We show that cosmic microwave background (CMB) observations have a strong potentiality not only as a test of cosmic kinematics but also as a gravity probe. We compare the recent high-resolution CMB data to models with a direct coupling of dark energy to dark matter. This extra interaction violates the equivalence principle, acts as an additional scalar gravity on dark matter fluctuations, and imprints a characteristic signature on the CMB spectra. Defining the ratio β of the dark energy interaction to gravity, we that β 〈 0.16 (95% confidence level [c.l.]) from the current CMB data set, regardless of the potential. This implies that the effective equation of state between equivalence and tracking has been close to the pure matter equation of state within 1% and that scalar gravity is at least 40 times weaker than tensor gravity. Furthermore, we show that an ideal CMB experiment limited by cosmic variance only can put an upper bound β 〈 0.05 (95% c.l.), comparable to the best limits provided by local gravity experiments on the coupling to baryons.
    Note: Gesehen am 17.11.2017
    In: The astrophysical journal. Part 2, Letters, London : Institute of Physics Publ., 1995, 583(2003,2) Seite L53-L56, 2041-8213
    In: volume:583
    In: year:2003
    In: number:2
    In: extent:4
    Language: English
    DOI: 10.1086/368064
    URL: Volltext
    URL: Volltext
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  • 7
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    First order phase transitions in cosmology (8)
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    UID:
    (DE-627)156549766X
    Format: 13
    Content: We review the observable effects produced by phase transitions occurring along with inflation. Firstly, we present a model which is able to generate a locally open universe as the result of a very early phase transition peaked at a precise epoch. Then, we show how the same model can produce primordial voids on the large scale structure, able to imprint in an observable way the microwave background. Finally, we speculate on the possibility of merging the two mechanisms in the same process.
    Note: Gesehen am 20.11.2017
    In: New astronomy, [Amsterdam] : Elsevier Science, 1996, 4(1999), 4, Seite 339-351
    In: volume:4
    In: year:1999
    In: number:4
    In: pages:339-351
    In: extent:13
    Language: English
    DOI: 10.1016/S1384-1076(99)00019-6
    URL: Volltext
    URL: Volltext
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  • 8
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    Statistical properties of the LEDA redshift database (1997)
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    UID:
    (DE-627)1565504011
    Format: 61
    Content: We present the statistical properties of large scale galaxy distribution in the LEDA redshift database. This catalog contains more than 40,000 redshifts over all the sky. We find that LEDA, although seriously affected by incompleteness, shows quite stable statistical properties. In particular, we have considered the behaviour of the two points correlation function and of the power spectrum of the density fluctuations, and we have done several tests to check whether the incompleteness of the catalog affect these statistical quantities. Our conclusion is that galaxy distribution in this catalog has fractal properties up to the distance 200 Mpc with D = 2.1 \pm 0.2, with no sign towards homogeneity: this result is statistically stable. We analyze also the properties of the angular distributions, finding a complete agreement with the results obtained in redshift space. Finally, we compare these results with those obtained in other redshift surveys, finding that this sample well reproduces the properties of galaxy distribution found in the different catalogs.
    Note: Gesehen am 20.11.2017
    In: De.arxiv.org, [Erscheinungsort nicht ermittelbar] : Arxiv.org, 1991, (1997) Artikel-Nummer 9711148, 61 Seiten
    In: year:1997
    In: extent:61
    Language: English
    URL: Volltext  (kostenfrei)
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  • 9
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    Reconstruction of the bubble nucleating potential (1996)
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    UID:
    (DE-627)1565537912
    Format: 19
    Content: We calculate analytically the bubble nucleation rate in a model of first order inflation which is able to produce large scale structure. The computation includes the first-order departure from the thin-wall limit, the explicit derivation of the pre-exponential factor, and the gravitational correction. The resulting bubble spectrum is then compared with constraints from the large scale structure and the microwave background. We show that there are models which pass all the constraints and produce bubble-like perturbations of interesting size. Furthermore, we show that it is in principle possible to reconstruct completely the inflationary two-field potential from observations.
    Note: Gesehen am 21.11.2017
    In: De.arxiv.org, [Erscheinungsort nicht ermittelbar] : Arxiv.org, 1991, (1996) Artikel-Nummer 9610038, 19 Seiten
    In: year:1996
    In: extent:19
    Language: English
    URL: Volltext  (kostenfrei)
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  • 10
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    Stochastic inflation : scaling solution for N fields (1993)
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    UID:
    (DE-627)1565551850
    Format: 18
    ISSN: 1361-6382
    Content: The Fokker-Planck equation for the primordial inflationary fluctuations is solved in the scaling approximation, when the classical drift dominates over the quantum diffusion. The scaling procedure is generalized to the case in which several fields are involved. The conditions imposed on the Kramers-Moyal coefficients in order to derive the scaling variables turn out to be fulfilled in some simple multi-field case. An analytical solution in the case of a two-field inflationary model is worked out.
    Note: Gesehen am 21.11.2017
    In: Classical and quantum gravity, Bristol : IOP Publ., 1984, 10(1993), 7, Seite 1267-1283, 1361-6382
    In: volume:10
    In: year:1993
    In: number:7
    In: pages:1267-1283
    In: extent:18
    Language: English
    DOI: 10.1088/0264-9381/10/7/006
    URL: Volltext
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