arXiv subjects

Jarah Evslin

Publications and source records attributed to Jarah Evslin.

At least 91 records · Page 5Linked to original sources

arXiv2017

Isolating the Lyman Alpha Forest BAO Anomaly

A 2.5-3 sigma discrepancy has been reported between the baryonic acoustic oscillation peak (BAO) in the Lyman $α$ forest at $z\sim 2.34$ and the best fit Planck $Λ$CDM cosmology. To isolate the origin of the tension, we consider unanchored BAO, in which the standard BAO ruler is not calibrated, eliminating any dependence on cosmology before redshift $z\sim 2.34$. We consider BOSS BAO measurements at $z\sim 0.32$, 0.57 and 2.34, using the full 2-dimensional constraints on the angular and line of sight BAO scale, as well as isotropic BAO measurements by 6dF and SDSS at $z\sim 0.106$ and $z\sim 0.15$. We find that the $z>0.43$ data alone is in 2.9 sigma of tension with $Λ$CDM with or without the Planck best fit values of the mass fraction $Ω_m$ and the BAO scale $r_d H_0$, indicating that the tension arises not from the $Λ$CDM parameters but from the dark energy evolution itself at 0.57<z<2.34. This conclusion is supported when the acoustic scale measured by the CMB is included, which further increases the tension and excludes a solution with a constant dark energy equation of state. Including the low $z$ BAO data, which is itself consistent with $Λ$CDM, reduces the tension to just over 2 sigma, however in this case a CPL parametrization of the dark energy evolution yields only a modest improvement.

astro-ph.CO↗

arXiv2016

Calibrating Effective Ia Supernova Magnitudes using the Distance Duality Relation

Using only Ia supernova (SN) observations, it is not possible to distinguish the evolution of the SN absolute magnitude $M_B$ from an arbitrary evolution of the Hubble parameter H(z). However, using Etherington's distance-duality relation, which relates the angular and luminosity distances, together with the observed angular baryon acoustic oscillation (BAO) scale at any redshift z, one may calibrate an effective M(z). This calibration involves a scale which depends on the cosmological model, however the evolution of the effective M(z) between two redshifts with BAO observations is independent of this scale. The line of sight BAO scale can be used to extend this calibration to redshifts near z. As an application, using BOSS BAO at z=0.32 and 2.34, JLA supernova at low $z$ and Hubble Space Telescope SN at z>1.7, we find a statistically insignificant downward shift M(2.34)-M(0.32)=-0.08$\pm$0.15. Replacing BOSS data with the best fit Planck LCDM BAO expectations, we find a shift of -0.24$\pm$0.13. With the SN that will be observed by the James Webb Space Telescope, such a calibration at z=2.34 will be more precise, and it will serve as an anchor for cosmological analyses with the SN that it will observe at yet higher z.

astro-ph.CO↗

arXiv2016

A Robust Measure of Dark Matter Halo Ellipticities

In simulations of the standard cosmological model (LCDM), dark matter halos are aspherical. However, so far the asphericity of an individual galaxy's halo has never been robustly established. We use the Jeans equations to define a quantity which robustly characterizes a deviation from rotational symmetry. This quantity is essentially the gravitational torque and it roughly provides the ellipticity projected along the line of sight. We show that the Thirty Meter Telescope (TMT), with a single epoch of observations combined with those of the Gaia space telescope, can distinguish the LCDM value of the torque from zero for each Sculptor-like dwarf galaxy with a confidence between 0 and 5 sigma, depending on the orientation of each halo. With two epochs of observations, TMT will achieve a 5 sigma discovery of torque and so asphericity for most such galaxies, and so will provide a new and powerful test of the LCDM model.

astro-ph.GA↗

arXiv2016

Symmetry Group and Group Representations Associated to the Thermodynamic Covariance Principle (TCP)

We describe the Lie group and the group representations associated to the nonlinear Thermodynamic Coordinate Transformations (TCT). The TCT guarantee the validity of the Thermodynamic Covariance Principle (TCP) : {\it The nonlinear closure equations, i.e. the flux-force relations, everywhere and in particular outside the Onsager region, must be covariant under TCT}. In other terms, the fundamental laws of thermodynamics should be manifestly covariant under transformations between the admissible thermodynamic forces, i.e. under TCT. The TCP ensures the validity of the fundamental theorems for systems far from equilibrium. The symmetry properties of a physical system are intimately related to the conservation laws characterizing that system. Noether's theorem gives a precise description of this relation. We derive the conserved (thermodynamic) currents and, as an example of calculation, a simple system out of equilibrium where the validity of TCP is imposed at the level of the kinetic equations is also analyzed.

cond-mat.mtrl-sci↗

arXiv2016

Sensitivity to the Neutrino Mass Hierarchy

In the next decade, a number of experiments will attempt to determine the neutrino mass hierarchy. Feasibility studies for such experiments generally determine the expected value of Delta chi^2. As the hierarchy is a discrete choice, Delta chi^2 does not obey a one degree of freedom chi^2 distribution and so the number of sigmas of confidence of the hierarchy determination is not the square root of the expected Delta chi^2. We present a simple formula for the sensitivity to the hierarchy that can be expected from the median experiment as a function of the expected Delta chi^2.

hep-ph↗

arXiv2016

Model-Independent Dark Energy Equation of State from Unanchored Baryon Acoustic Oscillations

Ratios of line of sight baryon acoustic oscillation (BAO) peaks at two redshifts only depend upon the average dark energy equation of states between those redshifts, as the dependence on anchors such as the BAO scale or the Hubble constant is canceled in a ratio. As a result, BAO ratios provide a probe of dark energy which is independent of both the cosmic distance ladder and the early evolution of universe. In this note, we use ratios to demonstrate that the known tension between the Lyman alpha forest BAO measurement and other probes arises entirely from recent (0.57<z<2.34) cosmological expansion. Using ratios of the line of sight Lyman alpha forest and BOSS CMASS BAO scales, we show that there is already more than 3 sigma tension with the standard LambdaCDM cosmological model which implies that either (i) The BOSS Lyman alpha forest measurement of the Hubble parameter was too low as a result of a statistical fluctuation or systematic error or else (ii) the dark energy equation of state falls steeply at high redshift.

astro-ph.CO↗

arXiv2016

The Leptonic CP Phase from T2(H)K and Muon Decay at Rest

Combining neutrino oscillations at T2K or T2HK with antineutrinos oscillations from muon decay at rest (DAR) allows a determination of the leptonic CP-violating phase delta. The degeneracies of this phase with theta13 and theta23 are broken and delta can be reliably distinguished from 180-delta. We present the sensitivity to delta of T2(H)K together with a muon DAR experiment using Super-K as a near detector and Hyper-K at the Tochibora site as a far detector.

hep-ph↗

arXiv2015

Neutrino Physics with Accelerator Driven Subcritical Reactors

Accelerator driven system (ADS) subcritical nuclear reactors are under development around the world. They will be intense sources of free, 30-50 MeV antimuon decay at rest antimuon neutrinos. These ADS reactor neutrinos can provide a robust test of the LSND anomaly and a precise measurement of the leptonic CP-violating phase delta, including sign(cos(delta)). The first phase of many ADS programs includes the construction of a low energy, high intensity proton or deuteron accelerator, which can yield competitive bounds on sterile neutrinos.

hep-ph↗

arXiv2015

Global two-monopoles

Global two-monopoles are unstable in their simplest formulation. We construct a model with a metric-like prefactor which we show can stabilize the global two-monopoles. The stabilizing construction is realized with a Skyrme sector where the metric-like prefactor is a function of the Skyrmion profile.

hep-th↗

arXiv2015

Determination of the Dynamic ITER Energy Confinement Time Scalings

We derive the differential equation, which is satisfied by the ITER scalings for the dynamic energy confinement time. We show that this differential equation can also be obtained from the differential equation for the energy confinement time, derived from the energy balance equation, when the plasma is near the steady state. We find that the values of the scaling parameters are linked to the second derivative of the power loss, estimated at the steady state. As an example of an application, the solution of the differential equation for the energy confinement time is compared with the profile obtained by solving numerically the balance equations (closed by a transport model) for a concrete Tokamak-plasma.

physics.plasm-ph↗

arXiv2015

Geometry and Dynamics of a Coupled 4D-2D Quantum Field Theory

Geometric and dynamical aspects of a coupled 4D-2D interacting quantum field theory - the gauged nonAbelian vortex - are investigated. The fluctuations of the internal 2D nonAbelian vortex zeromodes excite the massless 4D Yang-Mills modes and in general give rise to divergent energies. This means that the well-known 2D CP(N-1) zeromodes associated with a nonAbelian vortex become nonnormalizable. Moreover, all sorts of global, topological 4D effects such as the nonAbelian Aharonov-Bohm effect come into play. These topological global features and the dynamical properties associated with the fluctuation of the 2D vortex moduli modes are intimately correlated, as shown concretely here in a U(1) x SU(N) x SU(N) model with scalar fields in a bifundamental representation of the two SU(N) factor gauge groups.

hep-th↗

arXiv2015

Minimum Dissipation Principle in Nonlinear Transport

We extend Onsager's minimum dissipation principle to stationary states that are only subject to local equilibrium constraints, even when the transport coefficients depend on the thermodynamic forces. Crucial to this generalization is a decomposition of the thermodynamic forces into those that are held fixed by the boundary conditions, and the subspace which is orthogonal with respect to the metric defined by the transport coefficients. We are then able to apply Onsager and Machlup's proof to the second set of forces. As an example we consider two-dimensional nonlinear diffusion coupled to two reservoirs at different temperatures. Our extension differs from that of Bertini et al. in that we assume microscopic irreversibility and we allow a nonlinear dependence of the fluxes on the forces.

cond-mat.stat-mech↗

arXiv2015

Measuring theta12 Despite an Uncertain Reactor Neutrino Spectrum

The recently discovered 5 MeV bump highlights that the uncertainty in the reactor neutrino spectrum is far greater than some theoretical estimates. Medium baseline reactor neutrino experiments will deliver by far the most precise ever measurements of theta12. However, as a result of the bump, such a determination of theta12 using the theoretical spectrum would yield a value of sin^2(2theta12) which is more than 1% higher than the true value. We show that by using recent measurements of the reactor neutrino spectrum the precision of a measurement of theta12 at a medium baseline reactor neutrino experiment can be improved appreciably. We estimate this precision as a function of the 9Li spallation background veto efficiency and dead time.

hep-ph↗

arXiv2015

Vetoing Cosmogenic Muons in A Large Liquid Scintillator

At upcoming medium baseline reactor neutrino experiments the spallation 9Li background will be somewhat larger than the inverse beta decay reactor neutrino signal. We use new FLUKA simulations of spallation backgrounds to optimize a class of veto strategies and find that surprisingly the optimal veto for the mass hierarchy determination has a rejection efficiency below 90%. The unrejected background has only a modest effect on the physics goals. For example $Δχ^2$ for the hierarchy determination falls by 1.4 to 3 points depending on the muon tracking ability. The optimal veto strategy is essentially insensitive to the tracking ability, consisting of 2 meter radius, 1.1 second cylindrical vetoes of well tracked muons with showering energies above 3 to 4 GeV and 0.7 second full detector vetoes for poorly tracked muons above 15 to 18 GeV. On the other hand, as the uncertainty in theta12 will be dominated by the uncertainty in the reactor neutrino spectrum and not statistical fluctuations, the optimal rejection efficiency for the measurement of theta12 is 93% in the case of perfect tracking.

physics.ins-det↗

arXiv2015

What can Gaia (with TMT) say about Sculptor's Core?

Walker et al.'s Magellan/MMFS Survey survey identified 1355 red giant candidates in the dwarf spheroidal galaxy Sculptor. We find that the Gaia satellite will be able to measure the proper motions of 139 of these with a precision of between 13 and 20 km/s. Using a Jeans analysis and 5-parameter density model we show that this allows a determination of the mass within the deprojected half-light radius to within 16% and a measurement of the dark matter density exponent gamma to within 0.68 within that radius. If, even at first light, the TMT observes Sculptor then the combined observations will improve the precision on these proper motions to about 5 km/s, about 5 years earlier than would be possible without Gaia, further improving the precision of gamma to 0.27. Using a bimodal stellar population model for Sculptor the precision of gamma improves by about 30%. This suggests that Gaia (with TMT) is capable of excluding a cored profile of the kind predicted by CDM simulations with 2 sigma (4 sigma) of confidence.

astro-ph.GA↗

arXiv2014

Spherical T-duality II: An infinity of spherical T-duals for non-principal SU(2)-bundles

Recently we initiated the study of spherical T-duality for spacetimes that are principal SU(2)-bundles. In this paper, we extend spherical T-duality to spacetimes that are oriented non-principal SU(2)-bundles. There are several interesting new examples in this case and a new phenomenon appearing in the non-principal case is the existence of infinitely many spherical T-duals.

hep-th↗

arXiv2014

Showering Cosmogenic Muons in A Large Liquid Scintillator

We present the results of FLUKA simulations of the propagation of cosmogenic muons in a 20 kton spherical liquid scintillator detector underneath 700 to 900 meters of rock. A showering muon is one which deposits at least 3 GeV in the detector in addition to ionization energy. We find that 20 percent of muons are showering and a further 10 percent of muon events are muon bundles of which more than one muon enters the detector. In this range the showering and bundle fractions are robust against changes in the depth and topography, thus the total shower and bundle rate for a given experiment can be obtained by combining our results with an estimate for the total muon flux. One consequence is that a straightforward adaptation of the full detector showering muon cuts used by KamLAND to JUNO or RENO 50 would yield a nearly vanishing detector efficiency.

physics.ins-det↗

arXiv2014

The Leptonic CP Phase from Muon Decay at Rest with Two Detectors

We propose a novel experimental setup for the determination of the leptonic CP-violating phase delta using the decay at rest (DAR) of mu+ from a single source located at distances of 10 and 30 km from two 20 kton organic liquid scintillator detectors. The mu+ are created by bombarding a target with a 9 mA beam of 800 MeV protons. With this proposal delta can be determined with a precision of about 20 (15) degrees in 6 (12) years. In contrast with the DAEdALUS project, only a single source is required and it runs with a duty factor of 100 percent. Therefore 9 mA is the maximum instanteous current, greatly reducing both the technological challenges and the costs.

hep-ph↗