59,042 research outputs found
Large collective Lamb shift of two distant superconducting artificial atoms
Virtual photons can mediate interaction between atoms, resulting in an energy
shift known as a collective Lamb shift. Observing the collective Lamb shift is
challenging, since it can be obscured by radiative decay and direct atom-atom
interactions. Here, we place two superconducting qubits in a transmission line
terminated by a mirror, which suppresses decay. We measure a collective Lamb
shift reaching 0.8% of the qubit transition frequency and exceeding the
transition linewidth. We also show that the qubits can interact via the
transmission line even if one of them does not decay into it.Comment: 7+5 pages, 4+2 figure
Maximizing the Total Resolution of Graphs
A major factor affecting the readability of a graph drawing is its
resolution. In the graph drawing literature, the resolution of a drawing is
either measured based on the angles formed by consecutive edges incident to a
common node (angular resolution) or by the angles formed at edge crossings
(crossing resolution). In this paper, we evaluate both by introducing the
notion of "total resolution", that is, the minimum of the angular and crossing
resolution. To the best of our knowledge, this is the first time where the
problem of maximizing the total resolution of a drawing is studied.
The main contribution of the paper consists of drawings of asymptotically
optimal total resolution for complete graphs (circular drawings) and for
complete bipartite graphs (2-layered drawings). In addition, we present and
experimentally evaluate a force-directed based algorithm that constructs
drawings of large total resolution
Computing the lower and upper bounds of Laplace eigenvalue problem: by combining conforming and nonconforming finite element methods
This article is devoted to computing the lower and upper bounds of the
Laplace eigenvalue problem. By using the special nonconforming finite elements,
i.e., enriched Crouzeix-Raviart element and extension , we get
the lower bound of the eigenvalue. Additionally, we also use conforming finite
elements to do the postprocessing to get the upper bound of the eigenvalue. The
postprocessing method need only to solve the corresponding source problems and
a small eigenvalue problem if higher order postprocessing method is
implemented. Thus, we can obtain the lower and upper bounds of the eigenvalues
simultaneously by solving eigenvalue problem only once. Some numerical results
are also presented to validate our theoretical analysis.Comment: 19 pages, 4 figure
Exact Scaling Functions for Self-Avoiding Loops and Branched Polymers
It is shown that a recently conjectured form for the critical scaling
function for planar self-avoiding polygons weighted by their perimeter and area
also follows from an exact renormalization group flow into the branched polymer
problem, combined with the dimensional reduction arguments of Parisi and
Sourlas. The result is generalized to higher-order multicritical points,
yielding exact values for all their critical exponents and exact forms for the
associated scaling functions.Comment: 5 pages; v2: factors of 2 corrected; v.3: relation with existing
theta-point results clarified, some references added/update
On The Orbital Evolution of Jupiter Mass Protoplanet Embedded in A Self-Gravity Disk
We performed a series of hydro-dynamic simulations to investigate the orbital
migration of a Jovian planet embedded in a proto-stellar disk. In order to take
into account of the effect of the disk's self gravity, we developed and adopted
an \textbf{Antares} code which is based on a 2-D Godunov scheme to obtain the
exact Reimann solution for isothermal or polytropic gas, with non-reflecting
boundary conditions. Our simulations indicate that in the study of the runaway
(type III) migration, it is important to carry out a fully self consistent
treatment of the gravitational interaction between the disk and the embedded
planet. Through a series of convergence tests, we show that adequate numerical
resolution, especially within the planet's Roche lobe, critically determines
the outcome of the simulations. We consider a variety of initial conditions and
show that isolated, non eccentric protoplanet planets do not undergo type III
migration. We attribute the difference between our and previous simulations to
the contribution of a self consistent representation of the disk's self
gravity. Nevertheless, type III migration cannot be completely suppressed and
its onset requires finite amplitude perturbations such as that induced by
planet-planet interaction. We determine the radial extent of type III migration
as a function of the disk's self gravity.Comment: 19 pages, 13 figure
Discovery of a binary icosahedral quasicrystal in ScZn
We report the discovery of a new binary icosahedral phase in a Sc-Zn alloy
obtained through solution-growth, producing millimeter-sized, facetted, single
grain, quasicrystals that exhibit different growth morphologies, pentagonal
dodecahedra and rhombic triacontahedra, under only marginally different growth
conditions. These two morphologies manifest different degrees of
quasicrystalline order, or phason strain. The discovery of i-ScZn
suggests that a reexamination of binary phase diagrams at compositions close to
crystalline approximant structures may reveal other, new binary
quasicrystalline phases.Comment: Incorrect spelling in author list resolve
Ricci flow for homogeneous compact models of the universe
Using quaternions, we give a concise derivation of the Ricci tensor for
homogeneous spaces with topology of the 3-dimensional sphere. We derive
explicit and numerical solutions for the Ricci flow PDE and discuss their
properties. In the collapse (or expansion) of these models, the interplay of
the various components of the Ricci tensor are studied. We dedicate this paper
to honor the work of Josh Goldberg.Comment: 18 pages, 2 figure
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