BibSonomy publications for /https://www.bibsonomy.org/BibSonomy RSS feed for /2017-09-23T00:38:22+02:00MOND as a regime of quantum gravityhttps://www.bibsonomy.org/bibtex/252983345401d71af2c8200917a1ce205/vrepovrepo2017-09-22T17:03:17+02:00astronomy cosmology mond_theory quantum_gravity <span class="authorEditorList"><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Lee Smolin" itemprop="url" href="/person/1f053fae205bb537918d85f13fdf945d9/author/0"><span itemprop="name">L. Smolin</span></a></span>. </span>(<em><span>2017<meta content="2017" itemprop="datePublished"/></span></em>)<em>cite arxiv:1704.00780Comment: LaTex 22 pages, one figure. Thee revision contains many small improvements.</em>Fri Sep 22 17:03:17 CEST 2017cite arxiv:1704.00780Comment: LaTex 22 pages, one figure. Thee revision contains many small improvementsMOND as a regime of quantum gravity2017astronomy cosmology mond_theory quantum_gravity We propose that there is a regime of quantum gravity phenomena, for the case
that the cosmological constant is small and positive, which concerns phenomena
at temperatures below the deSitter temperature, or length scales larger than
the horizon. We observe that the standard form of the equivalence principle
does not apply in this regime; we consider instead that a weakened form of the
equivalence principle might hold in which the ratio of gravitational to
inertial mass is a function of environmental and global parameters. We consider
possible principles to determine that function. These lead to behaviour that,
in the limit of hbar to zero and the speed of light is taken to infinity,
reproduces the modifications of Newtonian dynamics first proposed by Milgrom.
Thus MOND is elucidated as coding the physics of a novel regime of quantum
gravity phenomena.
We propose also an effective description of this regime in terms of a
bi-metric theory, valid in the approximation where the metric is static. This
predicts a new effect, which modifies gravity for radial motions.[1704.00780] MOND as a regime of quantum gravityMONDian predictions for Newtonian M/L ratios for ultrafaint dSphshttps://www.bibsonomy.org/bibtex/26f9cd2623c2f7b2767b8cd99e8589f0b/vrepovrepo2017-09-22T17:01:48+02:00astronomy dsphs dwarf galaxy mond_theory <span class="authorEditorList"><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="R. A. M. Cortes" itemprop="url" href="/person/151d886e20ab8a16ab73e88d429e6ab09/author/0"><span itemprop="name">R. Cortes</span></a></span>, und <span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="X. Hernandez" itemprop="url" href="/person/151d886e20ab8a16ab73e88d429e6ab09/author/1"><span itemprop="name">X. Hernandez</span></a></span>. </span>(<em><span>2017<meta content="2017" itemprop="datePublished"/></span></em>)<em>cite arxiv:1705.06337Comment: 6 pages, 3 figures, accepted for publication in MNRAS.</em>Fri Sep 22 17:01:48 CEST 2017cite arxiv:1705.06337Comment: 6 pages, 3 figures, accepted for publication in MNRASMONDian predictions for Newtonian M/L ratios for ultrafaint dSphs2017astronomy dsphs dwarf galaxy mond_theory Under Newtonian gravity total masses for dSph galaxies will scale as $M_{T}
\propto R_{e} \sigma^{2}$, with $R_{e}$ the effective radius and $\sigma$ their
velocity dispersion. When both of the above quantities are available, the
resulting masses are compared to observed stellar luminosities to derive
Newtonian mass to light ratios, given a physically motivated proportionality
constant in the above expression. For local dSphs and the growing sample of
ultrafaint such systems, the above results in the largest mass to light ratios
of any galactic systems known, with values in the hundreds and even thousands
being common. The standard interpretation is for a dominant presence of an as
yet undetected dark matter component. If however, reality is closer to a
MONDian theory at the extremely low accelerations relevant to such systems,
$\sigma$ will scale with { stellar mass} $M_{*}^{1/4}$. This yields an
expression for the mass to light ratio which will be obtained under Newtonian
assumptions of $(M/L)_{N}=120 R_{e}(\Upsilon_{*}/L)^{1/2}$. Here we compare
$(M/L)_{N}$ values from this expression to Newtonian inferences for this ratios
for the actual $(R_{e}, \sigma, L)$ observed values for a sample of recently
observed ultrafaint dSphs, obtaining good agreement. Then, for systems where no
$\sigma$ values have been reported, we give predictions for the $(M/L)_{N}$
values which under a MONDian scheme are expected once kinematical observations
become available. For the recently studied Dragonfly 44 { and Crater II
systems}, reported $(M/L)_{N}$ values are also in good agreement with MONDian
expectations.[1705.06337] MONDian predictions for Newtonian M/L ratios for ultrafaint dSphsThe imprint of the MOND external field effect on the Oort cloud comets
aphelia distributionhttps://www.bibsonomy.org/bibtex/2626abef3e3d422c7ece97b1698ec7997/vrepovrepo2017-09-22T17:00:08+02:00astronomy comets cosmology mond_theory oort_cloud <span class="authorEditorList"><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="R. Paučo" itemprop="url" href="/person/1d96adc1f0e280b2ad3a61b73e9ea7a67/author/0"><span itemprop="name">R. Paučo</span></a></span>, und <span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="J. Klačka" itemprop="url" href="/person/1d96adc1f0e280b2ad3a61b73e9ea7a67/author/1"><span itemprop="name">J. Klačka</span></a></span>. </span>(<em><span>2017<meta content="2017" itemprop="datePublished"/></span></em>)<em>cite arxiv:1705.09273Comment: 8 pages, 4 figures, 2 tables; submitted to A&A, comments are welcome.</em>Fri Sep 22 17:00:08 CEST 2017cite arxiv:1705.09273Comment: 8 pages, 4 figures, 2 tables; submitted to A&A, comments are welcomeThe imprint of the MOND external field effect on the Oort cloud comets
aphelia distribution2017astronomy comets cosmology mond_theory oort_cloud Milgromian dynamics (MD or MOND) is a promising physical description
excelling especially in galaxies. When formulated as a modified gravity theory,
it leads to the so called external field effect (EFE). In the case of the solar
system this means that bodies orbiting the Sun are influenced, beyond its tidal
effect, by the external gravitational field of the Galaxy with magnitude
$\sim2\times10^{-10}$ m s$^{-2}$ and time-varying direction. Aphelia of
intermediate outer Oort cloud (OC) comets ($30<X<60,~X\equiv
10^{6}/a[\text{au}]$, where $a$ is semimajor axis) are distributed
non-uniformly on the celestial sphere, showing an apparent concentration around
a great circle centered at Galactic longitudes $L=-45$ and 135 deg. Such
non-uniformity is beyond that attributable to the classical injectors of
comets, stellar encounters and the Galactic tides, as well as the expected
observational biases. We investigated a hypothesis that the great circle
concentration of aphelia is a consequence of the long-term action of EFE in the
framework of MD. We considered exclusively quasi-linear MOND (QUMOND) theory.
We built our model of the OC in MD on an analytical approximation of the QUMOND
potential for a point mass in the dominant external field of constant
magnitude. The model is well applicable at heliocentric distances
$r\gtrsim10~000$ au. Constraints on the strength of EFE found by the analysis
of the Cassini radio-tracking data were taken into account. We demonstrated
characteristic imprint of the EFE on the distribution of aphelia of candidate
outer OC comets that migrated down to $r=10~000$ au. By both analytical and
numerical calculations, we showed that the combined effect of EFE and the
Galactic tides could qualitatively account for the characteristic features seen
in the observed distribution of aphelia of the outer OC comets.[1705.09273] The imprint of the MOND external field effect on the Oort cloud comets aphelia distributionMOND as a modification of Newtonian inertiahttps://www.bibsonomy.org/bibtex/2d29c645814888e70b6abae2f8beb5064/vrepovrepo2017-09-22T16:59:00+02:00astronomy cosmology mond_theory <span class="authorEditorList"><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="Mohammed Alzain" itemprop="url" href="/person/15f5e3249683700c8b187481bdf4f1b80/author/0"><span itemprop="name">M. Alzain</span></a></span>. </span>(<em><span>2017<meta content="2017" itemprop="datePublished"/></span></em>)<em>cite arxiv:1708.05385Comment: Accepted for publication in the Journal of Astrophysics and Astronomy.</em>Fri Sep 22 16:59:00 CEST 2017cite arxiv:1708.05385Comment: Accepted for publication in the Journal of Astrophysics and AstronomyMOND as a modification of Newtonian inertia2017astronomy cosmology mond_theory We present a modified inertia formulation of MOND without retaining Galilean
invariance. Assuming that the existence of a universal upper bound, predicted
by MOND, to the acceleration produced by a dark halo is equivalent to a
violation of the hypothesis of locality (which states that an accelerated
observer is pointwise inertial), we will demonstrate that Milgrom's law is
invariant under a new space-time coordinate transformation. In light of the new
coordinate symmetry, we will address the deficiency of MOND in resolving the
mass discrepancy problem in clusters of galaxies.[1708.05385] MOND as a modification of Newtonian inertiaUnderstanding disk galaxy rotation velocities without dark matter
contribution--a physical process for MOND?https://www.bibsonomy.org/bibtex/2ea92c035a9a5d8981131071d504fa52f/vrepovrepo2017-09-22T16:58:03+02:00astronomy astrophysics dark_matter galaxy mond_theory <span class="authorEditorList"><span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="K. Wilhelm" itemprop="url" href="/person/1d6eca764e41a13ac0126119ce8493077/author/0"><span itemprop="name">K. Wilhelm</span></a></span>, und <span itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author"><a title="B. N. Dwivedi" itemprop="url" href="/person/1d6eca764e41a13ac0126119ce8493077/author/1"><span itemprop="name">B. Dwivedi</span></a></span>. </span>(<em><span>2017<meta content="2017" itemprop="datePublished"/></span></em>)<em>cite arxiv:1709.02387Comment: 9 Pages; 3 Figures; 2 Tables.</em>Fri Sep 22 16:58:03 CEST 2017cite arxiv:1709.02387Comment: 9 Pages; 3 Figures; 2 TablesUnderstanding disk galaxy rotation velocities without dark matter
contribution--a physical process for MOND?2017astronomy astrophysics dark_matter galaxy mond_theory An impact model of gravity designed to emulate Newton's law of gravitation is
applied to the radial acceleration of disk galaxies. Based on this model
(Wilhelm et al. 2013), the rotation velocity curves can be understood without
the need to postulate any dark matter contribution. The increased acceleration
in the plane of the disk is a consequence of multiple interactions of gravitons
(called "quadrupoles" in the original paper) and the subsequent propagation in
this plane and not in three-dimensional space. The concept provides a physical
process that relates the fit parameter of the acceleration scale defined by
McGaugh et al. (2016) to the mean free path length of gravitons in the disks of
galaxies. It may also explain the modification of the gravitational interaction
at low acceleration levels in MOND (Milgrom 1983, 1994, 2015, 2016). Three
examples are discussed in some detail: The spiral galaxies NGC 7814, NGC 6503
and M 33.[1709.02387] Understanding disk galaxy rotation velocities without dark matter contribution--a physical process for MOND?