676 research outputs found
The Redshift-Space Cluster-Galaxy Cross-Correlation Function: I. Modeling Galaxy Infall onto Millennium Simulation Clusters and SDSS Groups
The large scale infall of galaxies around massive clusters provides a
potentially powerful diagnostic of structure growth, dark energy, and
cosmological deviations from General Relativity. We develop and test a method
to recover galaxy infall kinematics (GIK) from measurements of the
redshift-space cluster-galaxy cross-correlation function \xi_{cg}(r_p,r_\pi).
Using galaxy and halo samples from the Millennium simulation, we calibrate an
analytic model of the galaxy kinematic profiles comprised of a virialized
component with an isotropic Gaussian velocity distribution and an infall
component described by a skewed 2D t-distribution with a characteristic infall
velocity v_r and separate radial and tangential dispersions. We show that
convolving the real-space cross-correlation function with this velocity
distribution accurately predicts the redshift-space \xi_{cg}, and we show that
measurements of \xi_{cg} can be inverted to recover the four distinct elements
of the GIK profiles. These in turn provide diagnostics of cluster mass
profiles, and we expect the characteristic infall velocity v_r(r) in particular
to be insensitive to galaxy formation physics that can affect velocity
dispersions within halos. As a proof of concept we measure \xi_{cg} for rich
galaxy groups in the Sloan Digital Sky Survey and recover GIK profiles for
groups in two bins of central galaxy stellar mass. The higher mass bin has a
v_r(r) curve very similar to that of 10^{14} Msun halos in the Millennium
simulation, and the recovered kinematics follow the expected trends with mass.
GIK modeling of cluster-galaxy cross-correlations can be a valuable complement
to stacked weak lensing analyses, allowing novel tests of modified gravity
theories that seek to explain cosmic acceleration.Comment: Matched to the published version (adding one figure illustrating the
position and velocity vectors). For a brief video explaining the key result
of this paper, see https://www.youtube.com/watch?v=7RB49odfSGo, or
http://v.youku.com/v_show/id_XNDcxMDY3MTQ0.html in countries where YouTube is
not accessibl
Nodes and Spin Windings for Topological Transitions in Light-Matter Interactions: \\ Anisotropic Quantum Rabi Model as a Born Abstract Artist
By extracting different levels of topological information a new light is shed
on the energy spectrum of the anisotropic quantum Rabi model (QRM) which is the
fundamental model of light-matter interactions with indispensable
counter-rotating terms in ultra-strong couplings. Besides conventional
topological transitions (TTs) at gap closing, abundant unconventional TTs
including a particular one universal for different energy levels are unveiled
underlying level anticrossings without gap closing by tracking the
wave-function nodes. On the other hand, it is found that the nodes have a
correspondence to spin windings, which not only endows the nodes a more
explicit topological character in supporting single-qubit TTs but also turns
the topological information physically detectable. Furthermore, hidden
small-spin-knot transitions are exposed for the ground state, while more kinds
of spin-knot transitions emerge in excited states including unmatched node
numbers and spin winding numbers. As a surprise, frequently the spin windings
produce portraits in high spiritual similarity with abstract artistic works,
which demonstrates that the anisotropic QRM may be the Picasso of physical
models. This signifies that art is joining the dialogue between mathematics and
physics which was triggered by the milestone work of revealing integrability of
the QRM.Comment: 17 pages, 12 figure
Designing Electron Spin Textures and Spin Interferometers by Shape Deformations
We demonstrate that the spin orientation of an electron propagating in a
one-dimensional nanostructure with Rashba spin-orbit (SO) coupling can be
manipulated on demand by changing the geometry of the nanosystem. Shape
deformations that result in a non-uniform curvature give rise to complex
three-dimensional spin textures in space. We employ the paradigmatic example of
an elliptically deformed quantum ring to unveil the way to get an
all-geometrical and all-electrical control of the spin orientation. The
resulting spin textures exhibit a tunable topological character with windings
around the radial and the out-of-plane directions. We show that these
topologically non trivial spin patterns affect the spin interference effect in
the deformed ring, thereby resulting in different geometry-driven ballistic
electronic transport behaviors. Our results establish a deep connection between
electronic spin textures, spin transport and the nanoscale shape of the system.Comment: 8 pages, 4 figure
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