Posts Tagged confidence level

Recent Postings from confidence level

Imaging the redshifted 21-cm pattern around the first sources during the cosmic dawn using the SKA

Understanding properties of the first sources in the Universe using the redshifted \HI ~21-cm signal is one of the major aims of present and upcoming low-frequency experiments. We investigate the possibility of imaging the redshifted 21-cm pattern around the first sources during the cosmic dawn using the SKA1-low. We model the \HI ~21-cm image maps, appropriate for the SKA1-low, around the first sources consisting of stars and X-ray sources within galaxies. In addition to the system noise, we account also for the astrophysical foregrounds by adding them to the signal maps. We find that after subtracting the foregrounds using a polynomial fit and suppressing the noise by smoothing the maps over $10^{'} - 30^{'}$ angular scale, the isolated sources at $z \sim 15$ are detectable with $\sim 4 - 9 \, \sigma$ confidence level in 2000 h of observation with the SKA1-low. Although the 21-cm profiles around the sources get altered because of the Gaussian smoothing, the images can still be used to extract some of the source properties. We account for overlaps in the patterns of the individual sources by generating realistic \HI ~21-cm maps of the cosmic dawn that are based on $N$-body simulations and a one-dimensional radiative transfer code. We find that these sources should be detectable in the SKA1-low images at $z = 15$ with an SNR of $\sim 14 (4)$ in 2000 (200) h of observations. One possible observational strategy thus could be to observe multiple fields for shorter observation times, identify fields with SNR $\gtrsim 3$ and observe these fields for much longer duration. Such observations are expected to be useful in constraining the parameters related to the first sources.

Current and future constraints on Bekenstein-type models for varying couplings

Astrophysical tests of the stability of dimensionless fundamental couplings, such as the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu$, are an optimal probe of new physics. There is a growing interest in these tests, following indications of possible spacetime variations at the few parts per million level. Here we make use of the latest astrophysical measurements, combined with background cosmological observations, to obtain improved constraints on Bekenstein-type models for the evolution of both couplings. These are arguably the simplest models allowing for $\alpha$ and $\mu$ variations, and are characterized by a single free dimensionless parameter, $\zeta$, describing the coupling of the underlying dynamical degree of freedom to the electromagnetic sector. In the former case we find that this parameter is constrained to be $|\zeta_\alpha|<4.8\times10^{-6}$ (improving previous constraints by a factor of 6), while in the latter (which we quantitatively compare to astrophysical measurements for the first time) we find $\zeta_\mu=(2.7\pm3.1)\times10^{-7}$; both of these are at the $99.7\%$ confidence level. For $\zeta_\alpha$ this constraint is about 20 times stronger than the one obtained from local Weak Equivalence Principle tests, while for $\zeta_\mu$ it is about 2 orders of magnitude weaker. We also discuss the improvements on these constraints to be expected from the forthcoming ESPRESSO and ELT-HIRES spectrographs, conservatively finding a factor around 5 for the former and around 50 for the latter.

Current and future constraints on Bekenstein-type models for varying couplings [Cross-Listing]

Astrophysical tests of the stability of dimensionless fundamental couplings, such as the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu$, are an optimal probe of new physics. There is a growing interest in these tests, following indications of possible spacetime variations at the few parts per million level. Here we make use of the latest astrophysical measurements, combined with background cosmological observations, to obtain improved constraints on Bekenstein-type models for the evolution of both couplings. These are arguably the simplest models allowing for $\alpha$ and $\mu$ variations, and are characterized by a single free dimensionless parameter, $\zeta$, describing the coupling of the underlying dynamical degree of freedom to the electromagnetic sector. In the former case we find that this parameter is constrained to be $|\zeta_\alpha|<4.8\times10^{-6}$ (improving previous constraints by a factor of 6), while in the latter (which we quantitatively compare to astrophysical measurements for the first time) we find $\zeta_\mu=(2.7\pm3.1)\times10^{-7}$; both of these are at the $99.7\%$ confidence level. For $\zeta_\alpha$ this constraint is about 20 times stronger than the one obtained from local Weak Equivalence Principle tests, while for $\zeta_\mu$ it is about 2 orders of magnitude weaker. We also discuss the improvements on these constraints to be expected from the forthcoming ESPRESSO and ELT-HIRES spectrographs, conservatively finding a factor around 5 for the former and around 50 for the latter.

Current and future constraints on Bekenstein-type models for varying couplings [Cross-Listing]

Astrophysical tests of the stability of dimensionless fundamental couplings, such as the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu$, are an optimal probe of new physics. There is a growing interest in these tests, following indications of possible spacetime variations at the few parts per million level. Here we make use of the latest astrophysical measurements, combined with background cosmological observations, to obtain improved constraints on Bekenstein-type models for the evolution of both couplings. These are arguably the simplest models allowing for $\alpha$ and $\mu$ variations, and are characterized by a single free dimensionless parameter, $\zeta$, describing the coupling of the underlying dynamical degree of freedom to the electromagnetic sector. In the former case we find that this parameter is constrained to be $|\zeta_\alpha|<4.8\times10^{-6}$ (improving previous constraints by a factor of 6), while in the latter (which we quantitatively compare to astrophysical measurements for the first time) we find $\zeta_\mu=(2.7\pm3.1)\times10^{-7}$; both of these are at the $99.7\%$ confidence level. For $\zeta_\alpha$ this constraint is about 20 times stronger than the one obtained from local Weak Equivalence Principle tests, while for $\zeta_\mu$ it is about 2 orders of magnitude weaker. We also discuss the improvements on these constraints to be expected from the forthcoming ESPRESSO and ELT-HIRES spectrographs, conservatively finding a factor around 5 for the former and around 50 for the latter.

Current and future constraints on Bekenstein-type models for varying couplings [Cross-Listing]

Astrophysical tests of the stability of dimensionless fundamental couplings, such as the fine-structure constant $\alpha$ and the proton-to-electron mass ratio $\mu$, are an optimal probe of new physics. There is a growing interest in these tests, following indications of possible spacetime variations at the few parts per million level. Here we make use of the latest astrophysical measurements, combined with background cosmological observations, to obtain improved constraints on Bekenstein-type models for the evolution of both couplings. These are arguably the simplest models allowing for $\alpha$ and $\mu$ variations, and are characterized by a single free dimensionless parameter, $\zeta$, describing the coupling of the underlying dynamical degree of freedom to the electromagnetic sector. In the former case we find that this parameter is constrained to be $|\zeta_\alpha|<4.8\times10^{-6}$ (improving previous constraints by a factor of 6), while in the latter (which we quantitatively compare to astrophysical measurements for the first time) we find $\zeta_\mu=(2.7\pm3.1)\times10^{-7}$; both of these are at the $99.7\%$ confidence level. For $\zeta_\alpha$ this constraint is about 20 times stronger than the one obtained from local Weak Equivalence Principle tests, while for $\zeta_\mu$ it is about 2 orders of magnitude weaker. We also discuss the improvements on these constraints to be expected from the forthcoming ESPRESSO and ELT-HIRES spectrographs, conservatively finding a factor around 5 for the former and around 50 for the latter.

Cosmological and astrophysical constraints on tachyon dark energy models

Rolling tachyon field models are among the candidates suggested as explanations for the recent acceleration of the Universe. In these models the field is expected to interact with gauge fields and lead to variations of the fine-structure constant $\alpha$. Here we take advantage of recent observational progress and use a combination of background cosmological observations of Type Ia supernovas and astrophysical and local measurements of $\alpha$ to improve constraints on this class of models. We show that the constraints on $\alpha$ imply that the field dynamics must be extremely slow, leading to a constraint of the present-day dark energy equation of state $(1+w_0)<2.4\times10^{-7}$ at the $99.7\%$ confidence level. Therefore current and forthcoming standard background cosmology observational probes can't distinguish this class of models from a cosmological constant, while detections of $\alpha$ variations could possibly do so since they would have a characteristic redshift dependence.

Cosmological and astrophysical constraints on tachyon dark energy models [Cross-Listing]

Rolling tachyon field models are among the candidates suggested as explanations for the recent acceleration of the Universe. In these models the field is expected to interact with gauge fields and lead to variations of the fine-structure constant $\alpha$. Here we take advantage of recent observational progress and use a combination of background cosmological observations of Type Ia supernovas and astrophysical and local measurements of $\alpha$ to improve constraints on this class of models. We show that the constraints on $\alpha$ imply that the field dynamics must be extremely slow, leading to a constraint of the present-day dark energy equation of state $(1+w_0)<2.4\times10^{-7}$ at the $99.7\%$ confidence level. Therefore current and forthcoming standard background cosmology observational probes can't distinguish this class of models from a cosmological constant, while detections of $\alpha$ variations could possibly do so since they would have a characteristic redshift dependence.

Cosmological and astrophysical constraints on tachyon dark energy models [Cross-Listing]

Rolling tachyon field models are among the candidates suggested as explanations for the recent acceleration of the Universe. In these models the field is expected to interact with gauge fields and lead to variations of the fine-structure constant $\alpha$. Here we take advantage of recent observational progress and use a combination of background cosmological observations of Type Ia supernovas and astrophysical and local measurements of $\alpha$ to improve constraints on this class of models. We show that the constraints on $\alpha$ imply that the field dynamics must be extremely slow, leading to a constraint of the present-day dark energy equation of state $(1+w_0)<2.4\times10^{-7}$ at the $99.7\%$ confidence level. Therefore current and forthcoming standard background cosmology observational probes can't distinguish this class of models from a cosmological constant, while detections of $\alpha$ variations could possibly do so since they would have a characteristic redshift dependence.

Cosmological and astrophysical constraints on tachyon dark energy models [Cross-Listing]

Rolling tachyon field models are among the candidates suggested as explanations for the recent acceleration of the Universe. In these models the field is expected to interact with gauge fields and lead to variations of the fine-structure constant $\alpha$. Here we take advantage of recent observational progress and use a combination of background cosmological observations of Type Ia supernovas and astrophysical and local measurements of $\alpha$ to improve constraints on this class of models. We show that the constraints on $\alpha$ imply that the field dynamics must be extremely slow, leading to a constraint of the present-day dark energy equation of state $(1+w_0)<2.4\times10^{-7}$ at the $99.7\%$ confidence level. Therefore current and forthcoming standard background cosmology observational probes can't distinguish this class of models from a cosmological constant, while detections of $\alpha$ variations could possibly do so since they would have a characteristic redshift dependence.

Testing dark energy models with $H(z)$ data [Cross-Listing]

$Om(z)$ is a diagnostic approach to distinguish dark energy models. However, there are few articles to discuss what is the distinguishing criterion. In this paper, firstly we smooth the latest observational $H(z)$ data using a model-independent method -- Gaussian processes, and then reconstruct the $Om(z)$ and its fist order derivative $\mathcal{L}^{(1)}_m$. Such reconstructions not only could be the distinguishing criteria, but also could be used to estimate the authenticity of models. We choose some popular models to study, such as $\Lambda$CDM, generalized Chaplygin gas (GCG) model, Chevallier-Polarski-Linder (CPL) parametrization and Jassal-Bagla-Padmanabhan (JBP) parametrization. We plot the trajectories of $Om(z)$ and $\mathcal{L}^{(1)}_m$ with $1 \sigma$ confidence level of these models, and compare them to the reconstruction from $H(z)$ data set. The result indicates that the $H(z)$ data does not favor the CPL and JBP models at $1 \sigma$ confidence level. Strangely, in high redshift range, the reconstructed $\mathcal{L}^{(1)}_m$ has a tendency of deviation from theoretical value, which demonstrates these models are disagreeable with high redshift $H(z)$ data. This result supports the conclusions of \citet{sahni2014model} and \citet{ding2015there} that the $\Lambda$CDM may not be the best description of our universe.

Testing dark energy models with $H(z)$ data

$Om(z)$ is a diagnostic approach to distinguish dark energy models. However, there are few articles to discuss what is the distinguishing criterion. In this paper, firstly we smooth the latest observational $H(z)$ data using a model-independent method -- Gaussian processes, and then reconstruct the $Om(z)$ and its fist order derivative $\mathcal{L}^{(1)}_m$. Such reconstructions not only could be the distinguishing criteria, but also could be used to estimate the authenticity of models. We choose some popular models to study, such as $\Lambda$CDM, generalized Chaplygin gas (GCG) model, Chevallier-Polarski-Linder (CPL) parametrization and Jassal-Bagla-Padmanabhan (JBP) parametrization. We plot the trajectories of $Om(z)$ and $\mathcal{L}^{(1)}_m$ with $1 \sigma$ confidence level of these models, and compare them to the reconstruction from $H(z)$ data set. The result indicates that the $H(z)$ data does not favor the CPL and JBP models at $1 \sigma$ confidence level. Strangely, in high redshift range, the reconstructed $\mathcal{L}^{(1)}_m$ has a tendency of deviation from theoretical value, which demonstrates these models are disagreeable with high redshift $H(z)$ data. This result supports the conclusions of \citet{sahni2014model} and \citet{ding2015there} that the $\Lambda$CDM may not be the best description of our universe.

Testing dark energy models with $H(z)$ data [Replacement]

$Om(z)$ is a diagnostic approach to distinguish dark energy models. However, there are few articles to discuss what is the distinguishing criterion. In this paper, firstly we smooth the latest observational $H(z)$ data using a model-independent method -- Gaussian processes, and then reconstruct the $Om(z)$ and its fist order derivative $\mathcal{L}^{(1)}_m$. Such reconstructions not only could be the distinguishing criteria, but also could be used to estimate the authenticity of models. We choose some popular models to study, such as $\Lambda$CDM, generalized Chaplygin gas (GCG) model, Chevallier-Polarski-Linder (CPL) parametrization and Jassal-Bagla-Padmanabhan (JBP) parametrization. We plot the trajectories of $Om(z)$ and $\mathcal{L}^{(1)}_m$ with $1 \sigma$ confidence level of these models, and compare them to the reconstruction from $H(z)$ data set. The result indicates that the $H(z)$ data does not favor the CPL and JBP models at $1 \sigma$ confidence level. Strangely, in high redshift range, the reconstructed $\mathcal{L}^{(1)}_m$ has a tendency of deviation from theoretical value, which demonstrates these models are disagreeable with high redshift $H(z)$ data. This result supports the conclusions of Sahni et al. \citep{sahni2014model} and Ding et al. \citep{ding2015there} that the $\Lambda$CDM may not be the best description of our universe.

Testing dark energy models with $H(z)$ data [Replacement]

$Om(z)$ is a diagnostic approach to distinguish dark energy models. However, there are few articles to discuss what is the distinguishing criterion. In this paper, firstly we smooth the latest observational $H(z)$ data using a model-independent method -- Gaussian processes, and then reconstruct the $Om(z)$ and its fist order derivative $\mathcal{L}^{(1)}_m$. Such reconstructions not only could be the distinguishing criteria, but also could be used to estimate the authenticity of models. We choose some popular models to study, such as $\Lambda$CDM, generalized Chaplygin gas (GCG) model, Chevallier-Polarski-Linder (CPL) parametrization and Jassal-Bagla-Padmanabhan (JBP) parametrization. We plot the trajectories of $Om(z)$ and $\mathcal{L}^{(1)}_m$ with $1 \sigma$ confidence level of these models, and compare them to the reconstruction from $H(z)$ data set. The result indicates that the $H(z)$ data does not favor the CPL and JBP models at $1 \sigma$ confidence level. Strangely, in high redshift range, the reconstructed $\mathcal{L}^{(1)}_m$ has a tendency of deviation from theoretical value, which demonstrates these models are disagreeable with high redshift $H(z)$ data. This result supports the conclusions of Sahni et al. \citep{sahni2014model} and Ding et al. \citep{ding2015there} that the $\Lambda$CDM may not be the best description of our universe.

Testing CCDM Cosmology with the Radiation Temperature-Redshift Relation

The standard $\Lambda$CDM model can be mimicked at the background and perturbative levels (linear and non-linear) by a class of gravitationally induced particle production cosmology dubbed CCDM cosmology. However, the radiation component in the CCDM model follows a slightly different temperature-redshift $T(z)$-law which depends on an extra parameter, $\nu_r$, describing the subdominant photon production rate. Here we perform a statistical analysis based on a compilation of 36 recent measurements of $T(z)$ at low and intermediate redshifts. The likelihood of the production rate in CCDM cosmologies is constrained by $\nu_r = 0.023 \pm 0.027$ ($1\sigma$ confidence level, thereby showing that $\Lambda$CDM ($\nu_r=0$) is still compatible with the adopted data sample. Although being hardly differentiated in the dynamic sector (cosmic history and matter fluctuations), the so-called thermal sector (temperature law, abundances of thermal relics and CMB power spectrum) offers a clear possibility for crucial tests confronting $\Lambda$CDM and CCDM cosmologies.

Testing CCDM Cosmology with the Radiation Temperature-Redshift Relation [Cross-Listing]

The standard $\Lambda$CDM model can be mimicked at the background and perturbative levels (linear and non-linear) by a class of gravitationally induced particle production cosmology dubbed CCDM cosmology. However, the radiation component in the CCDM model follows a slightly different temperature-redshift $T(z)$-law which depends on an extra parameter, $\nu_r$, describing the subdominant photon production rate. Here we perform a statistical analysis based on a compilation of 36 recent measurements of $T(z)$ at low and intermediate redshifts. The likelihood of the production rate in CCDM cosmologies is constrained by $\nu_r = 0.023 \pm 0.027$ ($1\sigma$ confidence level, thereby showing that $\Lambda$CDM ($\nu_r=0$) is still compatible with the adopted data sample. Although being hardly differentiated in the dynamic sector (cosmic history and matter fluctuations), the so-called thermal sector (temperature law, abundances of thermal relics and CMB power spectrum) offers a clear possibility for crucial tests confronting $\Lambda$CDM and CCDM cosmologies.

First complete study of hadroproduction of a $\Upsilon$ meson associated with a prompt $J/\psi$ [Cross-Listing]

We present the first complete study of $\Upsilon$ and prompt $J/\psi$ production from single-parton scattering, including the complete $\mathcal{O}(\alpha_S^6)$ color-singlet contribution, the $\mathcal{O}(\alpha_S^2\alpha^2)$ electroweak contribution, the complete non-relativistic S-wave and P-wave color-octet contribution as well as the feeddown contribution. Our study motivated by the recent evidence reported by D0 collaboration of prompt $J/\psi$ and $\Upsilon$ simultaneous production at the Tevatron. With our complete evaluation, we are able to refine the determination of the double parton scattering contribution made by D0. We find that the effective cross section characterizing the importance of double-parton scatterings is $\sigma_{\rm eff}\le 8.2$ mb at $68\%$ confidence level from D0 measurement.

First complete study of hadroproduction of a $\Upsilon$ meson associated with a prompt $J/\psi$ [Cross-Listing]

We present the first complete study of $\Upsilon$ and prompt $J/\psi$ production from single-parton scattering, including the complete $\mathcal{O}(\alpha_S^6)$ color-singlet contribution, the $\mathcal{O}(\alpha_S^2\alpha^2)$ electroweak contribution, the complete non-relativistic S-wave and P-wave color-octet contribution as well as the feeddown contribution. Our study motivated by the recent evidence reported by D0 collaboration of prompt $J/\psi$ and $\Upsilon$ simultaneous production at the Tevatron. With our complete evaluation, we are able to refine the determination of the double parton scattering contribution made by D0. We find that the effective cross section characterizing the importance of double-parton scatterings is $\sigma_{\rm eff}\le 8.2$ mb at $68\%$ confidence level from D0 measurement.

First complete study of hadroproduction of a $\Upsilon$ meson associated with a prompt $J/\psi$

We present the first complete study of $\Upsilon$ and prompt $J/\psi$ production from single-parton scattering, including the complete $\mathcal{O}(\alpha_S^6)$ color-singlet contribution, the $\mathcal{O}(\alpha_S^2\alpha^2)$ electroweak contribution, the complete non-relativistic S-wave and P-wave color-octet contribution as well as the feeddown contribution. Our study motivated by the recent evidence reported by D0 collaboration of prompt $J/\psi$ and $\Upsilon$ simultaneous production at the Tevatron. With our complete evaluation, we are able to refine the determination of the double parton scattering contribution made by D0. We find that the effective cross section characterizing the importance of double-parton scatterings is $\sigma_{\rm eff}\le 8.2$ mb at $68\%$ confidence level from D0 measurement.

First complete study of hadroproduction of a $\Upsilon$ meson associated with a prompt $J/\psi$ [Cross-Listing]

We present the first complete study of $\Upsilon$ and prompt $J/\psi$ production from single-parton scattering, including the complete $\mathcal{O}(\alpha_S^6)$ color-singlet contribution, the $\mathcal{O}(\alpha_S^2\alpha^2)$ electroweak contribution, the complete non-relativistic S-wave and P-wave color-octet contribution as well as the feeddown contribution. Our study motivated by the recent evidence reported by D0 collaboration of prompt $J/\psi$ and $\Upsilon$ simultaneous production at the Tevatron. With our complete evaluation, we are able to refine the determination of the double parton scattering contribution made by D0. We find that the effective cross section characterizing the importance of double-parton scatterings is $\sigma_{\rm eff}\le 8.2$ mb at $68\%$ confidence level from D0 measurement.

A candidate optical counterpart to the middle-aged gamma-ray pulsar PSR J1741-2054 [Replacement]

We carried out deep optical observations of the middle-aged $\gamma$-ray pulsar PSR J1741-2054 with the Very Large Telescope (VLT). We identified two objects, of magnitudes $m_v=23.10\pm0.05$ and $m_v=25.32\pm0.08$, at positions consistent with the very accurate Chandra coordinates of the pulsar, the faintest of which is more likely to be its counterpart. From the VLT images we also detected the known bow-shock nebula around PSR J1741-2054. The nebula is displaced by $\sim 0\farcs9$ (at the $3\sigma$ confidence level) with respect to its position measured in archival data, showing that the shock propagates in the interstellar medium consistently with the pulsar proper motion. Finally, we could not find evidence of large-scale extended optical emission associated with the pulsar wind nebula detected by Chandra, down to a surface brightness limit of $\sim 28.1$ magnitudes arcsec$^{-2}$. Future observations are needed to confirm the optical identification of PSR J1741-2054 and characterise the spectrum of its counterpart.

A candidate optical counterpart to the middle-aged gamma-ray pulsar PSR J1741-2054

We carried out deep optical observations of the middle-aged $\gamma$-ray pulsar PSR J1741-2054 with the Very Large Telescope (VLT). We identified two objects, of magnitudes $m_v=23.10\pm0.05$ and $m_v=25.32\pm0.08$, at positions consistent with the very accurate Chandra coordinates of the pulsar, the faintest of which is more likely to be its counterpart. From the VLT images we also detected the known bow-shock nebula around PSR J1741-2054. The nebula is displaced by $\sim 0\farcs9$ (at the $3\sigma$ confidence level) with respect to its position measured in archival data, showing that the shock propagates in the interstellar medium consistently with the pulsar proper motion. Finally, we could not find evidence of large-scale extended optical emission associated with the pulsar wind nebula detected by Chandra, down to a surface brightness limit of $\sim 28.1$ magnitudes arcsec$^{-2}$. Future observations are needed to confirm the optical identification of \psr\ and characterise the spectrum of its counterpart.

Structural analysis of the Sextans dwarf spheroidal galaxy

We present wide-field $g$ and $i$ band stellar photometry of the Sextans dwarf spheroidal galaxy and its surrounding area out to four times its half-light radius ($r_h=695\,$pc), based on images obtained with the Dark Energy Camera at the 4-m Blanco telescope at CTIO. We find clear evidence of stellar substructure associated with the galaxy, extending to a distance of $82\arcmin$ (2\,kpc) from its centre. We perform a statistical analysis of the over-densities and find three distinct features, as well as an extended halo-like structure, to be significant at the $99.7\%$ confidence level or higher. Unlike the extremely elongated and extended substructures surrounding the Hercules dwarf spheroidal galaxy, the over-densities seen around Sextans are distributed evenly about its centre, and do not appear to form noticeable tidal tails. Fitting a King model to the radial distribution of Sextans stars yields a tidal radius $r_t =83.2\arcmin\pm7.1\arcmin$ (2.08$\pm$0.18\,kpc), which implies the majority of detected substructure is gravitationally bound to the galaxy. This finding suggests that Sextans is not undergoing significant tidal disruption from the Milky Way, supporting the scenario in which the orbit of Sextans has a low eccentricity.

Broadband short term variability of the quasar PDS 456

We present a detailed analysis of a recent $500$ ks net exposure \textit{Suzaku} observation, carried out in 2013, of the nearby ($z=0.184$) luminous (L$_{\rm bol}\sim10^{47}$ erg s$^{-1}$) quasar PDS 456 in which the X-ray flux was unusually low. The short term X-ray spectral variability has been interpreted in terms of variable absorption and/or intrinsic continuum changes. In the former scenario, the spectral variability is due to variable covering factors of two regions of partially covering absorbers. We find that these absorbers are characterised by an outflow velocity comparable to that of the highly ionised wind, i.e. $\sim0.25$ c, at the $99.9\%$ $(3.26\sigma)$ confidence level. This suggests that the partially absorbing clouds may be the denser clumpy part of the inhomogeneous wind. Following an obscuration event we obtained a direct estimate of the size of the X-ray emitting region, to be not larger than $20~R_{\rm g}$ in PDS 456.

Constraints on dark-matter properties from large-scale structure [Replacement]

We use large-scale cosmological observations to place constraints on the dark-matter pressure, sound speed and viscosity, and infer a limit on the mass of warm-dark-matter particles. Measurements of the cosmic microwave background (CMB) anisotropies constrain the equation of state and sound speed of the dark matter at last scattering at the per mille level. Since the redshifting of collisionless particles universally implies that these quantities scale like $a^{-2}$ absent shell crossing, we infer that today $w_{\rm (DM)}< 10^{-10.0}$, $c_{\rm s,(DM)}^2 < 10^{-10.7}$ and $c_{\rm vis, (DM)}^{2} < 10^{-10.3}$ at the $99\%$ confidence level. This very general bound can be translated to model-dependent constraints on dark-matter models: for warm dark matter these constraints imply $m> 70$ eV, assuming it decoupled while relativistic around the same time as the neutrinos; for a cold relic, we show that $m>100$ eV. We separately constrain the properties of the DM fluid on linear scales at late times, and find upper bounds $c_{\rm s, (DM)}^2<10^{-5.9}$, $c_{\rm vis, (DM)}^{2} < 10^{-5.7}$, with no detection of non-dust properties for the DM.

Constraints on dark-matter properties from large-scale structure [Replacement]

We use large-scale cosmological observations to place constraints on the dark-matter pressure, sound speed and viscosity, and infer a limit on the mass of warm-dark-matter particles. Measurements of the cosmic microwave background (CMB) anisotropies constrain the equation of state and sound speed of the dark matter at last scattering at the per mille level. Since the redshifting of collisionless particles universally implies that these quantities scale like $a^{-2}$ absent shell crossing, we infer that today $w_{\rm (DM)}< 10^{-10.0}$, $c_{\rm s,(DM)}^2 < 10^{-10.7}$ and $c_{\rm vis, (DM)}^{2} < 10^{-10.3}$ at the $99\%$ confidence level. This very general bound can be translated to model-dependent constraints on dark-matter models: for warm dark matter these constraints imply $m> 70$ eV, assuming it decoupled while relativistic around the same time as the neutrinos; for a cold relic, we show that $m>100$ eV. We separately constrain the properties of the DM fluid on linear scales at late times, and find upper bounds $c_{\rm s, (DM)}^2<10^{-5.9}$, $c_{\rm vis, (DM)}^{2} < 10^{-5.7}$, with no detection of non-dust properties for the DM.

Study of the rare decays of $B^0_s$ and $B^0$ into muon pairs from data collected during the LHC Run 1 with the ATLAS detector

A study of the decays $B^0\to \mu^+\mu^-$ and $B^0_s\to \mu^+\mu^-$ has been performed using data corresponding to an integrated luminosity of $25$ fb$^{-1}$ of $7$ TeV and $8$ TeV proton--proton collisions collected with the ATLAS detector during the LHC Run 1. For $B^0$, an upper limit on the branching fraction is set at ${\cal B}(B^0 \to \mu^+\mu^-) < 4.2 \times 10^{-10}$ at $95\%$ confidence level. For $B^0_s$, the branching fraction ${\cal B}(B^0_s \to \mu^+\mu^-) = \left( 0.9^{+1.1}_{-0.8} \right) \times 10^{-9}$ is measured. The results are consistent with the Standard Model expectation with a $p$-value of $4.8\%$, corresponding to $2.0$ standard deviations.

Measurement of the Double-Beta Decay Half-Life and Search for the Neutrinoless Double-Beta Decay of $^{48}{\rm Ca}$ with the NEMO-3 Detector [Replacement]

The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$\beta$ decay of $^{48}{\rm Ca}$. Using $5.25$ yr of data recorded with a $6.99\,{\rm g}$ sample of $^{48}{\rm Ca}$, approximately $150$ double-$\beta$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$\beta$ decay of $^{48}{\rm Ca}$ has been measured to be $T^{2\nu}_{1/2}\,=\,[6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)}] \times 10^{19}\,{\rm yr}$. A search for neutrinoless double-$\beta$ decay of $^{48}{\rm Ca}$ yields a null result and a corresponding lower limit on the half-life is found to be $T^{0\nu}_{1/2} > 2.0 \times 10^{22}\,{\rm yr}$ at $90\%$ confidence level, translating into an upper limit on the effective Majorana neutrino mass of $< m_{\beta\beta} > < 6.0 - 26$ ${\rm eV}$, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.

Measurement of the Double-Beta Decay Half-Life and Search for the Neutrinoless Double-Beta Decay of $^{48}{\rm Ca}$ with the NEMO-3 Detector

The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$\beta$ decay of $^{48}{\rm Ca}$. Using $5.25$\,yr of data recorded with a $6.99\,{\rm g}$ sample of $^{48}{\rm Ca}$, approximately $150$ double-$\beta$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$\beta$ decay of $^{48}{\rm Ca}$ has been measured to be \mbox{$T^{2\nu}_{1/2}\,=\,[6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)}] \times 10^{19}\,{\rm yr}$}. A search for neutrinoless double-$\beta$ decay of $^{48}{\rm Ca}$ yields a null result and a corresponding lower limit on the half-life is found to be $T^{0\nu}_{1/2} > 2.0 \times 10^{22}\,{\rm yr}$ at $90\%$ confidence level, translating into an upper limit on the effective Majorana neutrino mass of $< m_{\beta\beta} > < 6.0 - 26$\,${\rm eV}$, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.

Measurement of the Double-Beta Decay Half-Life and Search for the Neutrinoless Double-Beta Decay of $^{48}{\rm Ca}$ with the NEMO-3 Detector [Cross-Listing]

The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$\beta$ decay of $^{48}{\rm Ca}$. Using $5.25$\,yr of data recorded with a $6.99\,{\rm g}$ sample of $^{48}{\rm Ca}$, approximately $150$ double-$\beta$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$\beta$ decay of $^{48}{\rm Ca}$ has been measured to be \mbox{$T^{2\nu}_{1/2}\,=\,[6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)}] \times 10^{19}\,{\rm yr}$}. A search for neutrinoless double-$\beta$ decay of $^{48}{\rm Ca}$ yields a null result and a corresponding lower limit on the half-life is found to be $T^{0\nu}_{1/2} > 2.0 \times 10^{22}\,{\rm yr}$ at $90\%$ confidence level, translating into an upper limit on the effective Majorana neutrino mass of $< m_{\beta\beta} > < 6.0 - 26$\,${\rm eV}$, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.

Measurement of the double-beta decay half-life and search for the neutrinoless double-beta decay of $^{48}{\rm Ca}$ with the NEMO-3 detector [Replacement]

The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$\beta$ decay of $^{48}{\rm Ca}$. Using $5.25$ yr of data recorded with a $6.99\,{\rm g}$ sample of $^{48}{\rm Ca}$, approximately $150$ double-$\beta$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$\beta$ decay of $^{48}{\rm Ca}$ has been measured to be $T^{2\nu}_{1/2}\,=\,[6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)}] \times 10^{19}\,{\rm yr}$. A search for neutrinoless double-$\beta$ decay of $^{48}{\rm Ca}$ yields a null result and a corresponding lower limit on the half-life is found to be $T^{0\nu}_{1/2} > 2.0 \times 10^{22}\,{\rm yr}$ at $90\%$ confidence level, translating into an upper limit on the effective Majorana neutrino mass of $< m_{\beta\beta} > < 6.0 - 26$ ${\rm eV}$, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.

Measurement of the Double-Beta Decay Half-Life and Search for the Neutrinoless Double-Beta Decay of $^{48}{\rm Ca}$ with the NEMO-3 Detector [Replacement]

The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$\beta$ decay of $^{48}{\rm Ca}$. Using $5.25$ yr of data recorded with a $6.99\,{\rm g}$ sample of $^{48}{\rm Ca}$, approximately $150$ double-$\beta$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$\beta$ decay of $^{48}{\rm Ca}$ has been measured to be $T^{2\nu}_{1/2}\,=\,[6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)}] \times 10^{19}\,{\rm yr}$. A search for neutrinoless double-$\beta$ decay of $^{48}{\rm Ca}$ yields a null result and a corresponding lower limit on the half-life is found to be $T^{0\nu}_{1/2} > 2.0 \times 10^{22}\,{\rm yr}$ at $90\%$ confidence level, translating into an upper limit on the effective Majorana neutrino mass of $< m_{\beta\beta} > < 6.0 - 26$ ${\rm eV}$, with the range reflecting different nuclear matrix element calculations. Limits are also set on models involving Majoron emission and right-handed currents.

An optical transmission spectrum of the giant planet WASP-36 b

We present broad-band photometry of five transits in the planetary system WASP-36, totaling 17 high-precision light curves. Four of the transits were simultaneously observed in four passbands (g, r, i, z), using the telescope-defocussing technique, and achieving scatters of less than 1 mmag per observation. We used these data to improve the measured orbital and physical properties of the system, and obtain an optical transmission spectrum of the planet. We measured a decreasing radius from bluer to redder passbands with a confidence level of more than 5 sigma. The radius variation is roughly 11 pressure scale heights between the g and the z bands. This is too strong to be Rayleigh scattering in the planetary atmosphere, and implies the presence of a species which absorbs strongly at bluer wavelengths.

Search for QCD Instanton-Induced Processes at HERA in the High-$Q^2$ Domain [Cross-Listing]

Signals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$ GeV$^2$. The search is performed using H1 data corresponding to an integrated luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between $1.5$~pb and $6$~pb, at $95\%$~ confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging theory predictions.

Search for QCD Instanton-Induced Processes at HERA in the High-$Q^2$ Domain [Replacement]

Signals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$ GeV$^2$. The search is performed using H1 data corresponding to an integrated luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between $1.5$~pb and $6$~pb, at $95\%$~ confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging theory predictions.

Search for QCD Instanton-Induced Processes at HERA in the High-$Q^2$ Domain [Cross-Listing]

Signals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$ GeV$^2$. The search is performed using H1 data corresponding to an integrated luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between $1.5$~pb and $6$~pb, at $95\%$~ confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging theory predictions.

Search for QCD Instanton-Induced Processes at HERA in the High-$Q^2$ Domain [Replacement]

Signals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$ GeV$^2$. The search is performed using H1 data corresponding to an integrated luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between $1.5$~pb and $6$~pb, at $95\%$~ confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging theory predictions.

Search for QCD Instanton-Induced Processes at HERA in the High-$Q^2$ Domain

Signals of QCD instanton-induced processes are searched for in neutral current deep-inelastic scattering at the electron-proton collider HERA in the kinematic region defined by the Bjorken-scaling variable $x > 10^{-3}$, the inelasticity $0.2< y < 0.7$ and the photon virtuality $150 < Q^2 < 15000$ GeV$^2$. The search is performed using H1 data corresponding to an integrated luminosity of ~$351$ pb$^{-1}$. No evidence for the production of QCD instanton-induced events is observed. Upper limits on the cross section for instanton-induced processes between $1.5$~pb and $6$~pb, at $95\%$~ confidence level, are obtained depending on the kinematic domain in which instantons could be produced. Compared to earlier publications, the limits are improved by an order of magnitude and for the first time are challenging theory predictions.

Updated constraints on spatial variations of the fine-structure constant

Recent work by Webb {\it et al.} has provided indications of spatial variations of the fine-structure constant, $\alpha$, at a level of a few parts per million. Using a dataset of 293 archival measurements, they further show that a dipole provides a statistically good fit to the data, a result subsequently confirmed by other authors. Here we show that a more recent dataset of dedicated measurements further constrains these variations: although there are only 10 such measurements, their uncertainties are considerably smaller. We find that a dipolar variation is still a good fit to the combined dataset, but the amplitude of such a dipole must be somewhat smaller: $8.1\pm1.7$ ppm for the full dataset, versus $9.4\pm2.2$ ppm for the Webb {\it et al.} data alone, both at the $68.3\%$ confidence level. Constraints on the direction on the sky of such a dipole are also significantly improved. On the other hand the data can't yet discriminate between a pure spatial dipole and one with an additional redshift dependence.

Updated constraints on spatial variations of the fine-structure constant [Cross-Listing]

Recent work by Webb {\it et al.} has provided indications of spatial variations of the fine-structure constant, $\alpha$, at a level of a few parts per million. Using a dataset of 293 archival measurements, they further show that a dipole provides a statistically good fit to the data, a result subsequently confirmed by other authors. Here we show that a more recent dataset of dedicated measurements further constrains these variations: although there are only 10 such measurements, their uncertainties are considerably smaller. We find that a dipolar variation is still a good fit to the combined dataset, but the amplitude of such a dipole must be somewhat smaller: $8.1\pm1.7$ ppm for the full dataset, versus $9.4\pm2.2$ ppm for the Webb {\it et al.} data alone, both at the $68.3\%$ confidence level. Constraints on the direction on the sky of such a dipole are also significantly improved. On the other hand the data can't yet discriminate between a pure spatial dipole and one with an additional redshift dependence.

Updated constraints on spatial variations of the fine-structure constant [Cross-Listing]

Recent work by Webb {\it et al.} has provided indications of spatial variations of the fine-structure constant, $\alpha$, at a level of a few parts per million. Using a dataset of 293 archival measurements, they further show that a dipole provides a statistically good fit to the data, a result subsequently confirmed by other authors. Here we show that a more recent dataset of dedicated measurements further constrains these variations: although there are only 10 such measurements, their uncertainties are considerably smaller. We find that a dipolar variation is still a good fit to the combined dataset, but the amplitude of such a dipole must be somewhat smaller: $8.1\pm1.7$ ppm for the full dataset, versus $9.4\pm2.2$ ppm for the Webb {\it et al.} data alone, both at the $68.3\%$ confidence level. Constraints on the direction on the sky of such a dipole are also significantly improved. On the other hand the data can't yet discriminate between a pure spatial dipole and one with an additional redshift dependence.

Measurements of the Soft Gamma-ray Emission from SN2014J with Suzaku

The hard X-ray detector (HXD) onboard {\it Suzaku} measured soft $\gamma$-rays from the Type Ia supernova SN2014J at $77\pm2$ days after the explosion. Although the confidence level of the signal is about 90\% (i.e., $2 \sigma$), the $3 \sigma$ upper limit has been derived at $< 2.2 \times10^{-4}$ ph s$^{-1}$ cm$^{-2}$ in the 170 -- 250 keV band as the first independent measurement of soft $\gamma$-rays with an instrument other than {\it INTEGRAL}. For this analysis, we have examined the reproducibility of the NXB model of HXD/GSO using blank sky data. We find that the residual count rate in the 90 -- 500 keV band is distributed around an average of 0.19\% with a standard deviation of 0.42\% relative to the NXB rate. The averaged residual signals are consistent with that expected from the cosmic X-ray background. The flux of SN2014J derived from {\it Suzaku} measurements taken in one snapshot at $t=77\pm2$ days after the explosion is consistent with the {\it INTEGRAL} values averaged over the period between $t=$50 and 100 days and also with explosion models of single or double degenerate scenarios. Being sensitive to the total ejecta mass surrounding the radioactive material, the ratio between continuum and line flux in the soft gamma-ray regime might distinguish different progenitor models. The {\it Suzaku} data have been examined with this relation at $t=77\pm2$ days, but could not distinguish models between single and double degenerate-progenitors. We disfavor explosion models with larger $^{56}$Ni masses than 1 $M_\odot$, from our $1 \sigma$ error on the 170-250 keV X-ray flux of $(1.2\pm0.7) \times10^{-4}$ ph s$^{-1}$ cm$^{-2}$.

Constraining cosmic isotropy with type Ia supernovae

We investigate the validity of the Cosmological Principle by constraining the cosmological parameters $H_0$ and $q_0$ through the celestial sphere. Our analyses are performed in a low-redshift regime in order to follow a model independent approach, using both Union2.1 and JLA Type Ia Supernovae (SNe) compilations. We find that the preferred direction of the $H_0$ parameter in the sky is consistent with the bulk flow motion of our local Universe in the Union2.1 case, while the $q_0$ directional analysis seem to be anti-correlated with the $H_0$ for both data sets. Furthermore, we test the consistency of these results with Monte Carlo (MC) realisations, finding that the anisotropy on both parameters are significant within $2-3\sigma$ confidence level, albeit we find a significant correlation between the $H_0$ and $q_0$ mapping with the angular distribution of SNe from the JLA compilation. Therefore, we conclude that the detected anisotropies are either of local origin, or induced by the non-uniform celestial coverage of the SNe data set.

Constraining cosmic isotropy with type Ia supernovae [Cross-Listing]

We investigate the validity of the Cosmological Principle by constraining the cosmological parameters $H_0$ and $q_0$ through the celestial sphere. Our analyses are performed in a low-redshift regime in order to follow a model independent approach, using both Union2.1 and JLA Type Ia Supernovae (SNe) compilations. We find that the preferred direction of the $H_0$ parameter in the sky is consistent with the bulk flow motion of our local Universe in the Union2.1 case, while the $q_0$ directional analysis seem to be anti-correlated with the $H_0$ for both data sets. Furthermore, we test the consistency of these results with Monte Carlo (MC) realisations, finding that the anisotropy on both parameters are significant within $2-3\sigma$ confidence level, albeit we find a significant correlation between the $H_0$ and $q_0$ mapping with the angular distribution of SNe from the JLA compilation. Therefore, we conclude that the detected anisotropies are either of local origin, or induced by the non-uniform celestial coverage of the SNe data set.

Detection of a possible X-ray Quasi-periodic Oscillation in the Active Galactic Nucleus 1H~0707-495

Quasi-periodic oscillation (QPO) detected in the X-ray radiation of black hole X-ray binaries (BHXBs) is thought to originate from dynamical processes in the close vicinity of the black holes (BHs), and thus carries important physical information therein. Such a feature is extremely rare in active galactic nuclei (AGNs) with supermassive BHs. Here we report on the detection of a possible X-ray QPO signal with a period of 3800\,s at a confidence level $>99.99\%$ in the narrow-line Seyfert 1 galaxy (NLS1) 1H~0707-495 in one data set in 0.2-10\,keV taken with {\it XMM-Newton}. The statistical significance is higher than that of most previously reported QPOs in AGNs. The QPO is highly coherent (quality factor $Q=\nu/\Delta\nu \geqslant 15$) with a high rms fractional variability ($\sim15\%$). A comprehensive analysis of the optical spectra of this AGN is also performed, yielding a central BH mass $5.2\times10^6\,M_{\odot}$ from the broad emission lines based on the scaling relation. The QPO follows closely the known frequency-BH mass relation, which spans from stellar-mass to supermassive BHs. The absence of the QPO in other observations of the object suggests it a transient phenomenon. We suggest that the (high-frequency) QPOs tend to occur in highly accreting BH systems, from BHXBs to supermassive BHs. Future precise estimation of the BH mass may be used to infer the BH spin from the QPO frequency.

Neutrino observables from predictive flavour patterns

We look for predictive flavour patterns of the effective Majorana neutrino mass matrix that are compatible with current neutrino oscillation data. Our search is based on the assumption that the neutrino mass matrix contains equal elements and a minimal number of parameters, in the flavour basis where the charged lepton mass matrix is diagonal and real. Three unique patterns that can successfully explain neutrino observables at the $3\sigma$ confidence level with just three physical parameters are presented. Neutrino textures described by four and five parameters are also studied. The predictions for the lightest neutrino mass, the effective mass parameter in neutrinoless double beta decays and the CP-violating phases in the leptonic mixing are given.

Neutrino observables from predictive flavour patterns [Replacement]

We look for predictive flavour patterns of the effective Majorana neutrino mass matrix that are compatible with current neutrino oscillation data. Our search is based on the assumption that the neutrino mass matrix contains equal elements and a minimal number of parameters, in the flavour basis where the charged lepton mass matrix is diagonal and real. Three unique patterns that can successfully explain neutrino observables at the $3\sigma$ confidence level with just three physical parameters are presented. Neutrino textures described by four and five parameters are also studied. The predictions for the lightest neutrino mass, the effective mass parameter in neutrinoless double beta decays and the CP-violating phases in the leptonic mixing are given.

Dodging the cosmic curvature to probe the constancy of the speed of light [Cross-Listing]

We develop a new model-independent method to probe the constancy of the speed of light $c$. In our method, the degeneracy between the cosmic curvature and the speed of light can be eliminated, which makes the test more natural and general. Combining the independent observations of Hubble parameter $H(z)$ and luminosity distance $d_L(z)$, we use the model-independent smoothing technique, Gaussian processes, to reconstruct them and then detect variation of the speed of light. We find no signal of deviation from the present value of the speed of light $c_0$. Moreover, to demonstrate the improvement in probing the constancy of the speed of light from future experiments, we produce a series of simulated data. The Dark Energy Survey will be able to detect $\Delta c /c_0 \sim 4\%$ at $2\sigma$ confidence level. If the errors are reduced to one-tenth of the expected DES ones, it is easy to detect a $\Delta c /c_0 \sim 0.1\%$ variation at $2\sigma$ confidence level.

Dodging the cosmic curvature to probe the constancy of the speed of light

We develop a new model-independent method to probe the constancy of the speed of light $c$. In our method, the degeneracy between the cosmic curvature and the speed of light can be eliminated, which makes the test more natural and general. Combining the independent observations of Hubble parameter $H(z)$ and luminosity distance $d_L(z)$, we use the model-independent smoothing technique, Gaussian processes, to reconstruct them and then detect variation of the speed of light. We find no signal of deviation from the present value of the speed of light $c_0$. Moreover, to demonstrate the improvement in probing the constancy of the speed of light from future experiments, we produce a series of simulated data. The Dark Energy Survey will be able to detect $\Delta c /c_0 \sim 4\%$ at $2\sigma$ confidence level. If the errors are reduced to one-tenth of the expected DES ones, it is easy to detect a $\Delta c /c_0 \sim 0.1\%$ variation at $2\sigma$ confidence level.

The inflation models 2015

We provide the latest constraints on the power spectra of both scalar and tensor perturbations from the CMB data (including \textit{Planck}~2015, BICEP2 \& \textit{Keck Array} experiments) and the new BAO scales from SDSS-III BOSS observation. We find that the inflation model with a concave potential is preferred and both the inflation model with a monomial potential and the natural inflation model are marginally disfavored at around $95\%$ confidence level. But both the Brane inflation model and the Starobinsky inflation model fit the data quite well.

The inflation models 2015 [Cross-Listing]

We provide the latest constraints on the power spectra of both scalar and tensor perturbations from the CMB data (including \textit{Planck}~2015, BICEP2 \& \textit{Keck Array} experiments) and the new BAO scales from SDSS-III BOSS observation. We find that the inflation model with a concave potential is preferred and both the inflation model with a monomial potential and the natural inflation model are marginally disfavored at around $95\%$ confidence level. But both the Brane inflation model and the Starobinsky inflation model fit the data quite well.

 

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