14,348 research outputs found
Bulk Connectedness and Boundary Entanglement
We prove, for any state in a conformal field theory defined on a set of
boundary manifolds with corresponding classical holographic bulk geometry, that
for any bipartition of the boundary into two non-clopen sets, the density
matrix cannot be a tensor product of the reduced density matrices on each
region of the bipartition. In particular, there must be entanglement across the
bipartition surface. We extend this no-go theorem to general, arbitrary
partitions of the boundary manifolds into non-clopen parts, proving that the
density matrix cannot be a tensor product. This result gives a necessary
condition for states to potentially correspond to holographic duals.Comment: 12 pages, 2 figure
Two-body and three-body substructures served as building blocks in small spin-3 condensates
It was found that stable few-body spin-structures, pairs and triplexes, may
exist as basic constituents in small spin-3 condensates, and they will play the
role as building blocks when the parameters of interaction are appropriate.
Specific method is designed to find out these constituents.Comment: 9 pages, 4 figure
Entanglement Conservation, ER=EPR, and a New Classical Area Theorem for Wormholes
We consider the question of entanglement conservation in the context of the
ER=EPR correspondence equating quantum entanglement with wormholes. In quantum
mechanics, the entanglement between a system and its complement is conserved
under unitary operations that act independently on each; ER=EPR suggests that
an analogous statement should hold for wormholes. We accordingly prove a new
area theorem in general relativity: for a collection of dynamical wormholes and
black holes in a spacetime satisfying the null curvature condition, the maximin
area for a subset of the horizons (giving the largest area attained by the
minimal cross section of the multi-wormhole throat separating the subset from
its complement) is invariant under classical time evolution along the outermost
apparent horizons. The evolution can be completely general, including horizon
mergers and the addition of classical matter satisfying the null energy
condition. This theorem is the gravitational dual of entanglement conservation
and thus constitutes an explicit characterization of the ER=EPR duality in the
classical limit.Comment: 16 pages, 2 figure
Splitting Spacetime and Cloning Qubits: Linking No-Go Theorems across the ER=EPR Duality
We analyze the no-cloning theorem in quantum mechanics through the lens of
the proposed ER=EPR (Einstein-Rosen = Einstein-Podolsky-Rosen) duality between
entanglement and wormholes. In particular, we find that the no-cloning theorem
is dual on the gravity side to the no-go theorem for topology change, violating
the axioms of which allows for wormhole stabilization and causality violation.
Such a duality between important no-go theorems elucidates the proposed
connection between spacetime geometry and quantum entanglement.Comment: 6 pages, 2 figure
Entanglement of Purification and Multiboundary Wormhole Geometries
We posit a geometrical description of the entanglement of purification for
subregions in a holographic CFT. The bulk description naturally generalizes the
two-party case and leads to interesting inequalities among multi-party
entanglements of purification that can be geometrically proven from the
conjecture. Further, we study the relationship between holographic
entanglements of purification in locally-AdS3 spacetimes and entanglement
entropies in multi-throated wormhole geometries constructed via quotienting by
isometries. In particular, we derive new holographic inequalities for
geometries that are locally AdS3 relating entanglements of purification for
subregions and entanglement entropies in the wormhole geometries.Comment: 23 pages, 12 figures; v2 added references; v3 fixed inequality
direction in Eq.(2), expanded discussion - reflects published versio
Improved Simulation of the Mass Charging for ASTROD I
The electrostatic charging of the test mass in ASTROD I (Astrodynamical Space
Test of Relativity using Optical Devices I) mission can affect the quality of
the science data as a result of spurious Coulomb and Lorentz forces. To
estimate the size of the resultant disturbances, credible predictions of
charging rates and the charging noise are required. Using the GEANT4 software
toolkit, we present a detailed Monte Carlo simulation of the ASTROD I test mass
charging due to exposure of the spacecraft to galactic cosmic-ray (GCR) protons
and alpha particles (3He, 4He) in the space environment. A positive charging
rate of 33.3 e+/s at solar minimum is obtained. This figure reduces by 50% at
solar maximum. Based on this charging rate and factoring in the contribution of
minor cosmic-ray components, we calculate the acceleration noise and stiffness
associated with charging. We conclude that the acceleration noise arising from
Coulomb and Lorentz effects are well below the ASTROD I acceleration noise
limit at 0.1 mHz both at solar minimum and maximum. The coherent Fourier
components due to charging are investigated, it needs to be studied carefully
in order to ensure that these do not compromise the quality of science data in
the ASTROD I mission.Comment: 20 pages, 14 figures, submitted to International Journal of Modern
Physics
Mapping the Dirac point in gated bilayer graphene
We have performed low temperature scanning tunneling spectroscopy
measurements on exfoliated bilayer graphene on SiO2. By varying the back gate
voltage we observed a linear shift of the Dirac point and an opening of a band
gap due to the perpendicular electric field. In addition to observing a shift
in the Dirac point, we also measured its spatial dependence using spatially
resolved scanning tunneling spectroscopy. The spatial variation of the Dirac
point was not correlated with topographic features and therefore we attribute
its shift to random charged impurities.Comment: 3 pages, 3 figure
Spatially resolved spectroscopy of monolayer graphene on SiO2
We have carried out scanning tunneling spectroscopy measurements on
exfoliated monolayer graphene on SiO to probe the correlation between its
electronic and structural properties. Maps of the local density of states are
characterized by electron and hole puddles that arise due to long range
intravalley scattering from intrinsic ripples in graphene and random charged
impurities. At low energy, we observe short range intervalley scattering which
we attribute to lattice defects. Our results demonstrate that the electronic
properties of graphene are influenced by intrinsic ripples, defects and the
underlying SiO substrate.Comment: 6 pages, 7 figures, extended versio
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