60,115 research outputs found
Effective potentials for atom-atom interaction at low temperatures
We discuss the concept and design of effective atom-atom potentials that
accurately describe any physical processes involving only states around the
threshold. The existence of such potentials gives hope to a quantitative, and
systematic, understanding of quantum few-atom and quantum many-atom systems at
relatively low temperatures.Comment: 4 pages, 4 figure
From Electrons to Finite Elements: A Concurrent Multiscale Approach for Metals
We present a multiscale modeling approach that concurrently couples quantum
mechanical, classical atomistic and continuum mechanics simulations in a
unified fashion for metals. This approach is particular useful for systems
where chemical interactions in a small region can affect the macroscopic
properties of a material. We discuss how the coupling across different scales
can be accomplished efficiently, and we apply the method to multiscale
simulations of an edge dislocation in aluminum in the absence and presence of H
impurities.Comment: 4 page
Probabilistic teleportation of unknown two-particle state via POVM
We propose a scheme for probabilistic teleportation of unknown two-particle
state with partly entangled four-particle state via POVM. In this scheme the
teleportation of unknown two-particle state can be realized with certain
probability by performing two Bell state measurements, a proper POVM and a
unitary transformation.Comment: 5 pages, no figur
Compact Circularly Polarized Patch Antenna Using a Composite Right/Left-Handed Transmission Line Unit-Cell
A compact circularly polarized (CP) patch antenna using a composite right/left-handed (CRLH) transmission line (TL) unit-cell is proposed. The CRLH TL unit-cell includes a complementary split ring resonator (CSRR) for shunt inductance and a gap loaded with a circular-shaped slot for series capacitance. The CSRR can decrease the TM10 mode resonance frequency, thus reducing the electrical size of the proposed antenna. In addition, the asymmetry of the CSRR brings about the TM01 mode, which can be combined with the TM10 mode by changing the slot radius. The combination of these two orthogonal modes with 90° phase shift makes the proposed antenna provide a CP property. The experimental results show that the proposed antenna has a wider axial ratio bandwidth and a smaller electrical size than the reported CP antennas. Moreover, the proposed antenna is designed without impedance transformer, 90° phase shift, dual feed and ground via
Entropy in the NUT-Kerr-Newman Black Holes Due to an Arbitrary Spin Field
Membrane method is used to compute the entropy of the NUT-Kerr-Newman black
holes. It is found that even though the Euler characteristic is greater than
two, the Bekenstein-Hawking area law is still satisfied. The formula relating the entropy and the Euler characteristic becomes inapplicable for
non-extreme four dimensional NUT-Kerr-Newman black holes
A conjecture on the origin of dark energy
The physical origin of holographic dark energy (HDE) is investigated. The
main existing explanations, namely the UV/IR connection argument of Cohen et
al, Thomas' bulk holography argument, and Ng's spacetime foam argument, are
shown to be not satisfactory. A new explanation of the HDE model is then
proposed based on the ideas of Thomas and Ng. It is suggested that the dark
energy might originate from the quantum fluctuations of spacetime limited by
the event horizon of the universe. Several potential problems of the
explanation are also discussed.Comment: 11 pages, no figure
Search for Spin-Dependent Short-Range Force Using Optically Polarized He Gas
We propose a new method to detect short-range \textit{P-} and \textit{T-}
violating interactions between nucleons, based on measuring the precession
frequency shift of polarized He nuclei in the presence of an unpolarized
mass. To maximize the sensitivity, a high-pressure He cell with thin glass
windows (250 ) is used to minimize the distance between the mass and
He. The magnetic field fluctuation is suppressed by using the He gas in
a different region of the cell as a magnetometer. Systematic uncertainties from
the magnetic properties of the mass are suppressed by flipping both the
magnetic field and spin directions. Without any magnetic shielding, our result
has already reached the sensitivity of the current best limit. With improvement
in uniformity and stability of the field, we can further improve the
sensitivity by two orders of magnitude over the force range from
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