The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Sandhya Choubey - One of the best experts on this subject based on the ideXlab platform.
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updated bounds on sum of Neutrino Masses in various cosmological scenarios
Journal of Cosmology and Astroparticle Physics, 2018Co-Authors: Shouvik Roy Choudhury, Sandhya ChoubeyAbstract:We present strong bounds on the sum of three active Neutrino Masses (∑mν) using selected cosmological datasets and priors in various cosmological models. We use the following baseline datasets: Cosmic Microwave Background (CMB) temperature data from Planck 2015, Baryon Acoustic Oscillations measurements from SDSS-III BOSS DR12, the newly released Type Ia supernovae (SNe Ia) dataset from Pantheon Sample, and a prior on the optical depth to reionization from 2016 Planck Intermediate results. We constrain cosmological parameters with these datasets with a Bayesian analysis in the background of ΛCDM model with 3 massive active Neutrinos. For this minimal ΛCDM + ∑mν model we find a upper bound of ∑mν < 0.152 eV at 95% C.L. Adding the high-l polarization data from Planck strengthens this bound to ∑mν < 0.118 eV, which is very close to the minimum required mass of ∑mν 0.1 eV for inverted hierarchy. This bound is reduced to ∑mν < 0.110 eV when we also vary r, the tensor to scalar ratio (Λ CDM + r + ∑mν model), and add an additional dataset, BK14, the latest data released from the Bicep-Keck collaboration (which we add only when r is varied). This bound is further reduced to ∑mν < 0.101 eV in a cosmology with non-phantom dynamical dark energy (w0waCDM + ∑mν model with w(z)≥ −1 for all z). Considering the w0waCDM + r + ∑mν model and adding the BK14 data again, the bound can be even further reduced to ∑mν < 0.093 eV . For the w0wa CDM+∑mν model without any constraint on w(z), the bounds however relax to ∑mν < 0.276 eV . Adding a prior on the Hubble constant (H0 = 73.24±1.74 km/sec/Mpc) from Hubble Space Telescope (HST), the above mentioned bounds further improve to ∑mν < 0.117 eV, 0.091 eV, 0.085 eV, 0.082 eV, 0.078 eV and 0.247 eV respectively. This substantial improvement is mostly driven by a more than 3σ tension between Planck 2015 and HST measurements of H0 and should be taken cautiously.
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updated bounds on sum of Neutrino Masses in various cosmological scenarios
arXiv: Cosmology and Nongalactic Astrophysics, 2018Co-Authors: Shouvik Roy Choudhury, Sandhya ChoubeyAbstract:We present strong bounds on the sum of three active Neutrino Masses ($\sum m_{\nu}$) in various cosmological models. We use the following baseline datasets: CMB temperature data from Planck 2015, BAO measurements from SDSS-III BOSS DR12, the newly released SNe Ia dataset from Pantheon Sample, and a prior on the optical depth to reionization from 2016 Planck Intermediate results. We constrain cosmological parameters in $\Lambda CDM$ model with 3 massive active Neutrinos. For this $\Lambda CDM+\sum m_{\nu}$ model we find a upper bound of $\sum m_{\nu} <$ 0.152 eV at 95$\%$ C.L. Adding the high-$l$ polarization data from Planck strengthens this bound to $\sum m_{\nu} <$ 0.118 eV, which is very close to the minimum required mass of $\sum m_{\nu} \simeq$ 0.1 eV for inverted hierarchy. This bound is reduced to $\sum m_{\nu} <$ 0.110 eV when we also vary r, the tensor to scalar ratio ($\Lambda CDM+r+\sum m_{\nu}$ model), and add an additional dataset, BK14, the latest data released from the Bicep-Keck collaboration. This bound is further reduced to $\sum m_{\nu} <$ 0.101 eV in a cosmology with non-phantom dynamical dark energy ($w_0 w_a CDM+\sum m_{\nu}$ model with $w(z)\geq -1$ for all $z$). Considering the $w_0 w_a CDM+r+\sum m_{\nu}$ model and adding the BK14 data again, the bound can be even further reduced to $\sum m_{\nu} <$ 0.093 eV. For the $w_0 w_a CDM+\sum m_{\nu}$ model without any constraint on $w(z)$, the bounds however relax to $\sum m_{\nu} <$ 0.276 eV. Adding a prior on the Hubble constant ($H_0 = 73.24\pm 1.74$ km/sec/Mpc) from Hubble Space Telescope (HST), the above mentioned bounds further improve to $\sum m_{\nu} <$ 0.117 eV, 0.091 eV, 0.085 eV, 0.082 eV, 0.078 eV and 0.247 eV respectively. This substantial improvement is mostly driven by a more than 3$\sigma$ tension between Planck 2015 and HST measurements of $H_0$ and should be taken cautiously. (abstract abridged)
Irene Valenzuela - One of the best experts on this subject based on the ideXlab platform.
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constraining Neutrino Masses the cosmological constant and bsm physics from the weak gravity conjecture
Journal of High Energy Physics, 2017Co-Authors: Luis E. Ibáñez, Victor Martinlozano, Irene ValenzuelaAbstract:It is known that there are AdS vacua obtained from compactifying the SM to 2 or 3 dimensions. The existence of such vacua depends on the value of Neutrino Masses through the Casimir effect. Using the Weak Gravity Conjecture, it has been recently argued by Ooguri and Vafa that such vacua are incompatible with the SM embedding into a consistent theory of quantum gravity. We study the limits obtained for both the cosmological constant Λ4 and Neutrino Masses from the absence of such dangerous 3D and 2D SM AdS vacua. One interesting implication is that Λ4 is bounded to be larger than a scale of order m 4 , as observed experimentally. Interestingly, this is the first argument implying a non-vanishing Λ4 only on the basis of particle physics, with no cosmological input. Conversely, the observed Λ4 implies strong constraints on Neutrino Masses in the SM and also for some BSM extensions including extra Weyl or Dirac spinors, gravitinos and axions. The upper bounds obtained for Neutrino Masses imply (for fixed Neutrino Yukawa and Λ4) the existence of upper bounds on the EW scale. In the case of massive Majorana Neutrinos with a see-saw mechanism associated to a large scale M ≃ 1010 − 14 GeV and Yν1 ≃ 10−3, one obtains that the EW scale cannot exceed MEW ≲ 102 − 104 GeV. From this point of view, the delicate fine-tuning required to get a small EW scale would be a mirage, since parameters yielding higher EW scales would be in the swampland and would not count as possible consistent theories. This would bring a new perspective into the issue of the EW hierarchy.
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constraining Neutrino Masses the cosmological constant and bsm physics from the weak gravity conjecture
arXiv: High Energy Physics - Theory, 2017Co-Authors: Luis E. Ibáñez, Victor Martinlozano, Irene ValenzuelaAbstract:It is known that there are AdS vacua obtained from compactifying the SM to 2 or 3 dimensions. The existence of such vacua depends on the value of Neutrino Masses through the Casimir effect. Using the Weak Gravity Conjecture, it has been recently argued by Ooguri and Vafa that such vacua are incompatible with the SM embedding into a consistent theory of quantum gravity. We study the limits obtained for both the cosmological constant $\Lambda_4$ and Neutrino Masses from the absence of such dangerous 3D and 2D SM AdS vacua. One interesting implication is that $\Lambda_4$ is bounded to be larger than a scale of order $m_\nu^4$, as observed experimentally. Interestingly, this is the first argument implying a non-vanishing $\Lambda_4$ only on the basis of particle physics, with no cosmological input. Conversely, the observed $\Lambda_4$ implies strong constraints on Neutrino Masses in the SM and also for some BSM extensions including extra Weyl or Dirac spinors, gravitinos and axions. The upper bounds obtained for Neutrino Masses imply (for fixed Neutrino Yukawa and $\Lambda_4$) the existence of upper bounds on the EW scale. In the case of massive Majorana Neutrinos with a see-saw mechanism associated to a large scale $M\simeq 10^{10-14}$ GeV and $Y_{\nu_1}\simeq 10^{-3}$, one obtains that the EW scale cannot exceed $M_{EW}\lesssim 10^2-10^4$ GeV. From this point of view, the delicate fine-tuning required to get a small EW scale would be a mirage, since parameters yielding higher EW scales would be in the swampland and would not count as possible consistent theories. This would bring a new perspective into the issue of the EW hierarchy.
Luis E. Ibáñez - One of the best experts on this subject based on the ideXlab platform.
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constraining Neutrino Masses the cosmological constant and bsm physics from the weak gravity conjecture
arXiv: High Energy Physics - Theory, 2017Co-Authors: Luis E. Ibáñez, Victor Martinlozano, Irene ValenzuelaAbstract:It is known that there are AdS vacua obtained from compactifying the SM to 2 or 3 dimensions. The existence of such vacua depends on the value of Neutrino Masses through the Casimir effect. Using the Weak Gravity Conjecture, it has been recently argued by Ooguri and Vafa that such vacua are incompatible with the SM embedding into a consistent theory of quantum gravity. We study the limits obtained for both the cosmological constant $\Lambda_4$ and Neutrino Masses from the absence of such dangerous 3D and 2D SM AdS vacua. One interesting implication is that $\Lambda_4$ is bounded to be larger than a scale of order $m_\nu^4$, as observed experimentally. Interestingly, this is the first argument implying a non-vanishing $\Lambda_4$ only on the basis of particle physics, with no cosmological input. Conversely, the observed $\Lambda_4$ implies strong constraints on Neutrino Masses in the SM and also for some BSM extensions including extra Weyl or Dirac spinors, gravitinos and axions. The upper bounds obtained for Neutrino Masses imply (for fixed Neutrino Yukawa and $\Lambda_4$) the existence of upper bounds on the EW scale. In the case of massive Majorana Neutrinos with a see-saw mechanism associated to a large scale $M\simeq 10^{10-14}$ GeV and $Y_{\nu_1}\simeq 10^{-3}$, one obtains that the EW scale cannot exceed $M_{EW}\lesssim 10^2-10^4$ GeV. From this point of view, the delicate fine-tuning required to get a small EW scale would be a mirage, since parameters yielding higher EW scales would be in the swampland and would not count as possible consistent theories. This would bring a new perspective into the issue of the EW hierarchy.
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constraining Neutrino Masses the cosmological constant and bsm physics from the weak gravity conjecture
Journal of High Energy Physics, 2017Co-Authors: Luis E. Ibáñez, Victor Martinlozano, Irene ValenzuelaAbstract:It is known that there are AdS vacua obtained from compactifying the SM to 2 or 3 dimensions. The existence of such vacua depends on the value of Neutrino Masses through the Casimir effect. Using the Weak Gravity Conjecture, it has been recently argued by Ooguri and Vafa that such vacua are incompatible with the SM embedding into a consistent theory of quantum gravity. We study the limits obtained for both the cosmological constant Λ4 and Neutrino Masses from the absence of such dangerous 3D and 2D SM AdS vacua. One interesting implication is that Λ4 is bounded to be larger than a scale of order m 4 , as observed experimentally. Interestingly, this is the first argument implying a non-vanishing Λ4 only on the basis of particle physics, with no cosmological input. Conversely, the observed Λ4 implies strong constraints on Neutrino Masses in the SM and also for some BSM extensions including extra Weyl or Dirac spinors, gravitinos and axions. The upper bounds obtained for Neutrino Masses imply (for fixed Neutrino Yukawa and Λ4) the existence of upper bounds on the EW scale. In the case of massive Majorana Neutrinos with a see-saw mechanism associated to a large scale M ≃ 1010 − 14 GeV and Yν1 ≃ 10−3, one obtains that the EW scale cannot exceed MEW ≲ 102 − 104 GeV. From this point of view, the delicate fine-tuning required to get a small EW scale would be a mirage, since parameters yielding higher EW scales would be in the swampland and would not count as possible consistent theories. This would bring a new perspective into the issue of the EW hierarchy.
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Neutrino Masses and Mixings from String Theory Instantons
Journal of High Energy Physics, 2007Co-Authors: Stefan Antusch, Luis E. Ibáñez, Tommaso MacrìAbstract:We study possible patterns of Neutrino Masses and mixings in string models in which Majorana Neutrino Masses are generated by a certain class of string theory instantons recently considered in the literature. These instantons may generate either directly the dim=5 Weinberg operator or right-handed Neutrino Majorana Masses, both with a certain flavour-factorised form. A hierarchy of Neutrino Masses naturally appears from the exponentially suppressed contributions of different instantons. The flavour structure is controlled by string amplitudes involving Neutrino fields and charged instanton zero modes. For some simple choices for these amplitudes one finds Neutrino mixing patterns consistent with experimental results. In particular, we find that a tri-bimaximal mixing pattern is obtained for simple symmetric values of the string correlators.
Steen Hannestad - One of the best experts on this subject based on the ideXlab platform.
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Neutrino Masses and cosmic radiation density combined analysis
Journal of Cosmology and Astroparticle Physics, 2006Co-Authors: Steen Hannestad, Georg G RaffeltAbstract:We determine the range of Neutrino Masses and cosmic radiation content allowed by the most recent CMB and large-scale structure data. In contrast to other recent works, we vary these parameters simultaneously and provide likelihood contours in the two-dimensional parameter space of Neff, the usual effective number of Neutrino species measuring the radiation density, and ??m?. The allowed range of ??m? has shrunk significantly compared to previous studies. The previous degeneracy between these parameters has disappeared, largely thanks to the baryon acoustic oscillation data. The likelihood contours differ significantly if ??m? resides in a single species instead of the standard case of being equally distributed among all flavours. For ??m??=?0 we find 2.7?
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Neutrino Masses and cosmic radiation density combined analysis
arXiv: Astrophysics, 2006Co-Authors: Steen Hannestad, Georg G RaffeltAbstract:We determine the range of Neutrino Masses and cosmic radiation content allowed by the most recent CMB and large-scale structure data. In contrast to other recent works, we vary these parameters simultaneously and provide likelihood contours in the two-dimensional parameter space of N_eff}, the usual effective number of Neutrino species measuring the radiation density, and \sum m_nu. The allowed range of \sum m_nu and N_eff has shrunk significantly compared to previous studies. The previous degeneracy between these parameters has disappeared, largely thanks to the baryon acoustic oscillation data. The likelihood contours differ significantly if \sum m_nu resides in a single species instead of the standard case of being equally distributed among all flavors. For \sum m_nu=0 we find 2.7 < N_eff < 4.6 at 95% CL while \sum m_nu < 0.62 eV at 95% CL for the standard radiation content.
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measuring Neutrino Masses and dark energy with weak lensing tomography
Journal of Cosmology and Astroparticle Physics, 2006Co-Authors: Steen Hannestad, Huitzu Tu, Yvonne Y Y WongAbstract:Surveys of weak gravitational lensing of distant galaxies will be one of the key cosmological probes in the future. We study the ability of such surveys to constrain Neutrino Masses and the equation of state parameter of dark energy, focusing on how tomographic information can improve the sensitivity to these parameters. We also provide a detailed discussion of systematic effects pertinent to weak lensing surveys, and the possible degradation of sensitivity to cosmological parameters due to these effects. For future probes such as the Large Synoptic Survey Telescope survey, we find that, when combined with cosmic microwave background data from the Planck satellite, a sensitivity to Neutrino Masses of can be reached. These results are not affected by variations in the running of the scalar spectral index, the time-dependence of the dark energy equation of state, and/or the number of relativistic degrees of freedom.
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measuring Neutrino Masses and dark energy with weak lensing tomography
arXiv: Astrophysics, 2006Co-Authors: Steen Hannestad, Yvonne Y Y WongAbstract:Surveys of weak gravitational lensing of distant galaxies will be one of the key cosmological probes in the future. We study the ability of such surveys to constrain Neutrino Masses and the equation of state parameter of the dark energy, focussing on how tomographic information can improve the sensitivity to these parameters. We also provide a detailed discussion of systematic effects pertinent to weak lensing surveys, and the possible degradation of sensitivity to cosmological parameters due to these effects. For future probes such as the Large Synoptic Survey Telescope survey, we find that, when combined with cosmic microwave background data from the Planck satellite, a sensitivity to Neutrino Masses of sigma(sum m_nu) < 0.05 eV can be reached. This results is robust against variations in the running of the scalar spectral index, the time-dependence of dark energy equation of state, and/or the number of relativistic degrees of freedom.
Tommaso Macrì - One of the best experts on this subject based on the ideXlab platform.
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Neutrino Masses and Mixings from String Theory Instantons
Journal of High Energy Physics, 2007Co-Authors: Stefan Antusch, Luis E. Ibáñez, Tommaso MacrìAbstract:We study possible patterns of Neutrino Masses and mixings in string models in which Majorana Neutrino Masses are generated by a certain class of string theory instantons recently considered in the literature. These instantons may generate either directly the dim=5 Weinberg operator or right-handed Neutrino Majorana Masses, both with a certain flavour-factorised form. A hierarchy of Neutrino Masses naturally appears from the exponentially suppressed contributions of different instantons. The flavour structure is controlled by string amplitudes involving Neutrino fields and charged instanton zero modes. For some simple choices for these amplitudes one finds Neutrino mixing patterns consistent with experimental results. In particular, we find that a tri-bimaximal mixing pattern is obtained for simple symmetric values of the string correlators.