LIVIVO - The Search Portal for Life Sciences

zur deutschen Oberfläche wechseln
Advanced search

Search results

Result 1 - 10 of total 15

Search options

  1. Article: Neutrino masses and the dark energy equation of state: relaxing the cosmological neutrino mass bound.

    Hannestad, Steen

    Physical review letters

    2005  Volume 95, Issue 22, Page(s) 221301

    Abstract: At present, cosmology provides the nominally strongest constraint on the masses of standard model neutrinos. However, this constraint is extremely dependent on the nature of the dark energy component of the Universe. When the dark energy equation of ... ...

    Abstract At present, cosmology provides the nominally strongest constraint on the masses of standard model neutrinos. However, this constraint is extremely dependent on the nature of the dark energy component of the Universe. When the dark energy equation of state parameter is taken as a free (but constant) parameter, the neutrino mass bound is sigma m(v) < or = 1.48 eV (95% C.L.), compared with sigma m(v) < or = 0.65 eV (95% C.L.) in the standard model where the dark energy is in the form of a cosmological constant. This has important consequences for future experiments aimed at the direct measurement of neutrino masses. We also discuss prospects for future cosmological measurements of neutrino masses.
    Language English
    Publishing date 2005-11-25
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.95.221301
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Bonn / Germany

    Z 4' 58/153: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  2. Book ; Online: Efficient calculation of cosmological neutrino clustering with both linear and non-linear gravity

    Archidiacono, Maria / Hannestad, Steen

    2015  

    Abstract: We study in detail how neutrino perturbations can be followed in linear theory by using only terms up to $l=2$ in the Boltzmann hierarchy. We provide a new approximation to the third moment and demonstrate that the neutrino power spectrum can be ... ...

    Abstract We study in detail how neutrino perturbations can be followed in linear theory by using only terms up to $l=2$ in the Boltzmann hierarchy. We provide a new approximation to the third moment and demonstrate that the neutrino power spectrum can be calculated to a precision of better than $\sim$ 5% for masses up to $\sim$ 1 eV. The matter and CMB power spectra can be calculated far more precisely and typically at least a factor of a few better than with existing approximations. We then proceed to study how the neutrino power spectrum can be reliably calculated even in the presence of non-linear gravitational clustering by using the full non-linear gravitational potential derived from semi-analytic methods based on $N$-body simulations in the Boltzmann evolution hierarchy. Our results agree extremely well with results derived from $N$-body simulations.

    Comment: 12 pages, 7 figures
    Keywords Astrophysics - Cosmology and Nongalactic Astrophysics
    Subject code 621
    Publishing date 2015-10-10
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  3. Article ; Online: New constraints on neutrino physics from BOOMERANG data

    Hannestad

    Physical review letters

    2000  Volume 85, Issue 20, Page(s) 4203–4206

    Abstract: We have performed a likelihood analysis of the recent data on the cosmic microwave background radiation anisotropy from the BOOMERANG experiment. These data place a strong upper bound on the radiation density present at recombination. Expressed in terms ... ...

    Abstract We have performed a likelihood analysis of the recent data on the cosmic microwave background radiation anisotropy from the BOOMERANG experiment. These data place a strong upper bound on the radiation density present at recombination. Expressed in terms of the equivalent number of neutrino species the 2sigma bound is N(nu)</=13. This bound is not flavor sensitive. It also applies to the Universe at a much later epoch, and as such places severe limits on scenarios with decaying neutrinos. The bound also yields a firm upper limit on the lepton asymmetry in the Universe.<br />
    Language English
    Publishing date 2000-11-13
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.85.4203
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Bonn / Germany

    Z 4' 58/153: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  4. Article ; Online: How self-interactions can reconcile sterile neutrinos with cosmology.

    Hannestad, Steen / Hansen, Rasmus Sloth / Tram, Thomas

    Physical review letters

    2014  Volume 112, Issue 3, Page(s) 31802

    Abstract: Short baseline neutrino oscillation experiments have shown hints of the existence of additional sterile neutrinos in the eV mass range. However, such neutrinos seem incompatible with cosmology because they have too large of an impact on cosmic structure ... ...

    Abstract Short baseline neutrino oscillation experiments have shown hints of the existence of additional sterile neutrinos in the eV mass range. However, such neutrinos seem incompatible with cosmology because they have too large of an impact on cosmic structure formation. Here we show that new interactions in the sterile neutrino sector can prevent their production in the early Universe and reconcile short baseline oscillation experiments with cosmology.
    Language English
    Publishing date 2014-01-24
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.112.031802
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Bonn / Germany

    Z 4' 58/153: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  5. Article: New supernova limit on large extra dimensions: bounds on Kaluza-Klein graviton production.

    Hannestad, S / Raffelt, G G

    Physical review letters

    2001  Volume 87, Issue 5, Page(s) 51301

    Abstract: If large extra dimensions exist in nature, supernova (SN) cores will emit large fluxes of Kaluza-Klein gravitons, producing a cosmic background of these particles with energies and masses up to about 100 MeV. Radiative decays then give rise to a diffuse ... ...

    Abstract If large extra dimensions exist in nature, supernova (SN) cores will emit large fluxes of Kaluza-Klein gravitons, producing a cosmic background of these particles with energies and masses up to about 100 MeV. Radiative decays then give rise to a diffuse cosmic gamma-ray background with E(gamma) approximately less than 100 MeV which is well in excess of the observations if more than 0.5%-1% of the SN energy is emitted into the new channel. For two extra dimensions we derive a conservative bound on their radius of R approximately less than 0.9 x 10(-4) mm; for three extra dimensions it is R approximately less than 1.9 x 10(-7) mm.
    Language English
    Publishing date 2001-07-30
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.87.051301
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Bonn / Germany

    Z 4' 58/153: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  6. Book ; Online: $\nu\scriptstyle{\rm CO}N{\rm CEPT}$

    Dakin, Jeppe / Brandbyge, Jacob / Hannestad, Steen / Haugbølle, Troels / Tram, Thomas

    Cosmological neutrino simulations from the non-linear Boltzmann hierarchy

    2017  

    Abstract: In this paper the non-linear effect of massive neutrinos on cosmological structures is studied in a conceptually new way. We have solved the non-linear continuity and Euler equations for the neutrinos on a grid in real space in $N$-body simulations, and ... ...

    Abstract In this paper the non-linear effect of massive neutrinos on cosmological structures is studied in a conceptually new way. We have solved the non-linear continuity and Euler equations for the neutrinos on a grid in real space in $N$-body simulations, and closed the Boltzmann hierarchy at the non-linear Euler equation using the stress and pressure perturbations from linear theory. By comparing with state-of-the art cosmological neutrino simulations, we are able to simulate the non-linear neutrino power spectrum very accurately. This translates into a negligible error in the matter power spectrum, and so our $\scriptstyle{\rm CO}N{\rm CEPT}$ code is ideally suited for extracting the neutrino mass from future high precision non-linear observational probes such as Euclid.

    Comment: Accepted for publication in JCAP. 29 pages, 10 figures
    Keywords Astrophysics - Cosmology and Nongalactic Astrophysics ; High Energy Physics - Phenomenology
    Subject code 621
    Publishing date 2017-12-11
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  7. Book ; Online: Grid Based Linear Neutrino Perturbations in Cosmological N-body Simulations

    Brandbyge, Jacob / Hannestad, Steen

    2008  

    Abstract: We present a novel, fast and precise method for including the effect of light neutrinos in cosmological N-body simulations. The effect of the neutrino component is included by using the linear theory neutrino perturbations in the calculation of the ... ...

    Abstract We present a novel, fast and precise method for including the effect of light neutrinos in cosmological N-body simulations. The effect of the neutrino component is included by using the linear theory neutrino perturbations in the calculation of the gravitational potential in the N-body simulation. By comparing this new method with the full non-linear evolution first presented in \cite{Brandbyge1}, where the neutrino component was treated as particles, we find that the new method calculates the matter power spectrum with an accuracy better than 1% for \sum m_\nu \lesssim 0.5 eV at z = 0. This error scales approximately as (\sum m_\nu)^2, making the new linear neutrino method extremely accurate for a total neutrino mass in the range 0.05 - 0.3 eV. At z = 1 the error is below 0.3% for \sum m_\nu \lesssim 0.5 eV and becomes negligible at higher redshifts. This new method is computationally much more efficient than representing the neutrino component by N-body particles.

    Comment: 17 pages, 15 figures
    Keywords Astrophysics
    Subject code 621
    Publishing date 2008-12-17
    Publishing country us
    Document type Book ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

    Full text online

    More links

    Kategorien

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  8. Article: Stringent neutron-star limits on large extra dimensions.

    Hannestad, Steen / Raffelt, Georg G

    Physical review letters

    2002  Volume 88, Issue 7, Page(s) 71301

    Abstract: Supernovae (SNe) are copious sources for Kaluza-Klein (KK) gravitons which are generic for theories with large extra dimensions. These massive particles are produced with average velocities approximately 0.5c so that many of them are gravitationally ... ...

    Abstract Supernovae (SNe) are copious sources for Kaluza-Klein (KK) gravitons which are generic for theories with large extra dimensions. These massive particles are produced with average velocities approximately 0.5c so that many of them are gravitationally retained by the SN core. Every neutron star thus has a halo of KK gravitons which decay into nu(nu), e(+)e(-), and gammagamma on time scales approximately 10(9) years. The EGRET gamma-flux limits (E(gamma) approximately 100 MeV) for nearby neutron stars constrain the compactification scale for n = 2 extra dimensions to M > or = 500 TeV, and M > or = 30 TeV for n = 3. The requirement that neutron stars are not excessively heated by KK decays implies M > or = 1700 TeV for n = 2, and M > or = 60 TeV for n = 3.
    Language English
    Publishing date 2002-02-18
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.88.071301
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Bonn / Germany

    Z 4' 58/153: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  9. Article: Seesaw mechanism for scalar fields as possible basis for dark energy.

    Enqvist, Kari / Hannestad, Steen / Sloth, Martin S

    Physical review letters

    2007  Volume 99, Issue 3, Page(s) 31301

    Abstract: We propose a novel mechanism for dark energy, based on an extended seesaw for scalar fields, which does not require any new physics at energies below the TeV scale. A very light quintessence mass is usually considered to be technically unnatural, unless ... ...

    Abstract We propose a novel mechanism for dark energy, based on an extended seesaw for scalar fields, which does not require any new physics at energies below the TeV scale. A very light quintessence mass is usually considered to be technically unnatural, unless it is protected by some symmetry broken at the new very light scale. We propose that one can use an extended seesaw mechanism to construct technically natural models for very light fields, protected by supersymmetry softly broken above a TeV.
    Language English
    Publishing date 2007-07-20
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.99.031301
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Bonn / Germany

    Z 4' 58/153: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

  10. Article ; Online: Nucleosynthesis and the mass of the tau neutrino.

    Hannestad / Madsen

    Physical review letters

    1996  Volume 76, Issue 16, Page(s) 2848–2851

    Language English
    Publishing date 1996-04-15
    Publishing country United States
    Document type Journal Article
    ZDB-ID 208853-8
    ISSN 1079-7114 ; 0031-9007
    ISSN (online) 1079-7114
    ISSN 0031-9007
    DOI 10.1103/PhysRevLett.76.2848
    Database MEDical Literature Analysis and Retrieval System OnLINE

    More links

    Kategorien

    In stock of ZB MED Bonn / Germany

    Z 4' 58/153: Show issues

    Order via subito

    This service is chargeable due to the Delivery terms set by subito. Orders including an article and supplementary material will be classified as separate orders. In these cases, fees will be demanded for each order.

    Inter-library loan at ZB MED

    Your chosen title can be delivered directly to ZB MED Cologne location if you are registered as a user at ZB MED Cologne.

To top