7,726 research outputs found
Resource-Efficient Chemistry on Quantum Computers with the Variational Quantum Eigensolver and the Double Unitary Coupled-Cluster Approach.
Applications of quantum simulation algorithms to obtain electronic energies of molecules on noisy intermediate-scale quantum (NISQ) devices require careful consideration of resources describing the complex electron correlation effects. In modeling second-quantized problems, the biggest challenge confronted is that the number of qubits scales linearly with the size of the molecular basis. This poses a significant limitation on the size of the basis sets and the number of correlated electrons included in quantum simulations of chemical processes. To address this issue and enable more realistic simulations on NISQ computers, we employ the double unitary coupled-cluster (DUCC) method to effectively downfold correlation effects into the reduced-size orbital space, commonly referred to as the active space. Using downfolding techniques, we demonstrate that properly constructed effective Hamiltonians can capture the effect of the whole orbital space in small-size active spaces. Combining the downfolding preprocessing technique with the variational quantum eigensolver, we solve for the ground-state energy of H2, Li2, and BeH2 in the cc-pVTZ basis using the DUCC-reduced active spaces. We compare these results to full configuration-interaction and high-level coupled-cluster reference calculations
A New Supersymmetric Compactification of Chiral IIB Supergravity
We present a new compactification of chiral, N=2 ten-dimensional supergravity
down to five dimensions and show that it corresponds to the N=2 supersymmetric
critical point of five-dimensional, N=8 gauged supergravity found in [KPW].
This solution presented here is of particular significance because it involves
non-zero tensor gauge fields and, via the AdS/CFT correspondence, is dual to
the non-trivial N=1 supersymmetric fixed point of N=4 Yang-Mills theory.Comment: 14 pages, references added, some typos correcte
Error-proof programmable self-assembly of DNA-nanoparticle clusters
We study theoretically a new generic scheme of programmable self-assembly of
nanoparticles into clusters of desired geometry. The problem is motivated by
the feasibility of highly selective DNA-mediated interactions between colloidal
particles. By analyzing both a simple generic model and a more realistic
description of a DNA-colloidal system, we demonstrate that it is possible to
suppress the glassy behavior of the system, and to make the self-assembly
nearly error-proof. This regime requires a combination of stretchable
interparticle linkers (e.g. sufficiently long DNA), and a soft repulsive
potential. The jamming phase diagram and the error probability are computed for
several types of clusters. The prospects for the experimental implementation of
our scheme are also discussed. PACS numbers: 81.16.Dn, 87.14.Gg, 36.40.EiComment: 6 pages, 4 figures, v2: substantially revised version, added journal
re
New Vacua of Gauged N=8 Supergravity
We analyze a particular SU(2) invariant sector of the scalar manifold of
gauged N=8 supergravity in five dimensions, and find all the critical points of
the potential within this sector. The critical points give rise to Anti-de
Sitter vacua, and preserve at least an SU(2) gauge symmetry. Consistent
truncation implies that these solutions correspond to Anti-de Sitter
compactifications of IIB supergravity, and hence to possible near-horizon
geometries of 3-branes. Thus we find new conformal phases of softly broken N=4
Yang--Mills theory. One of the critical points preserves N=2 supersymmetry in
the bulk and is therefore completely stable, and corresponds to an N=1
superconformal fixed point of the Yang--Mills theory. The corresponding
renormalization group flow from the N=4 point has c_{IR}/c_{UV} = 27/32. We
also discuss the ten-dimensional geometries corresponding to these critical
points.Comment: 14 pages, 1 table, harvma
Cx26 keratitis ichthyosis deafness syndrome mutations trigger alternative splicing of Cx26 to prevent expression and cause toxicity in vitro
The Cx26 mRNA has not been reported to undergo alternative splicing. In expressing a series of human keratitis ichthyosis deafness (KID) syndrome mutations of Cx26 (A88V, N14K and A40V), we found the production of a truncated mRNA product. These mutations, although not creating a cryptic splice site, appeared to activate a pre-existing cryptic splice site. The alternative splicing of the mutant Cx26 mRNA could be prevented by mutating the predicted 3′, 5′ splice sites and the branch point. The presence of a C-terminal fluorescent protein tag (mCherry or Clover) was necessary for this alternative splicing to occur. Strangely, Cx26A88V could cause the alternative splicing of co-expressed WT Cx26—suggesting a trans effect. The alternative splicing of Cx26A88V caused cell death, and this could be prevented by the 3′, 5′ and branch point mutations. Expression of the KID syndrome mutants could be rescued by combining them with removal of the 5′ splice site. We used this strategy to enable expression of Cx26A40V-5′ and demonstrate that this KID syndrome mutation removed CO2 sensitivity from the Cx26 hemichannel. This is the fourth KID syndrome mutation found to abolish the CO2-sensitivity of the Cx26 hemichannel, and suggests that the altered CO2-sensitivity could contribute to the pathology of this mutation. Future research on KID syndrome mutations should take care to avoid using a C-terminal tag to track cellular localization and expression or if this is unavoidable, combine this mutation with removal of the 5′ splice site
Statistical Mechanics of DNA-Mediated Colloidal Aggregation
We present a statistical mechanical model of aggregation in colloidal systems
with DNA mediated interactions. We obtain a general result for the two-particle
binding energy in terms of the hybridization free energy of DNA and
two model dependent properties: the average number of available DNA bridges
\left and the effective DNA conccentration . We calculate
these parameters for a particular DNA bridging scheme. The fraction of all the
-mers, including the infinite aggregate, are shown to be universal functions
of a single parameter directly related to the two-particle binding energy. We
explicitly take into account the partial ergodicity of the problem resulting
from the slow DNA binding-unbinding dynamics, and introduce the concept of
angular localization of DNA linkers. In this way, we obtain a direct link
between DNA thermodynamics and the global aggregation and melting properties in
DNA-colloidal systems. The results of the theory are shown to be in
quantitative agreement with two recent experiments with particles of micron and
nanometer size.
PACS numbers: 81.16.Dn, 82.20.Db, 68.65.-k, 87.14.GgComment: 12 pages, 6 figures, v2: added reference, expanded conclusion, added
journal re
An upper limit to the dry merger rate at <z> ~ 0.55
We measure the fraction of Luminous Red Galaxies (LRGs) in dynamically close
pairs (with projected separation less than 20 kpc and velocity
difference less than 500 km s) to estimate the dry merger rate for
galaxies with and
in the 2dF-SDSS LRG and QSO (2SLAQ) redshift survey. For galaxies with a
luminosity ratio of or greater we determine a upper limit to
the merger fraction of 1.0% and a merger rate of
Mpc Gyr (assuming that all pairs merge on the shortest possible
timescale set by dynamical friction). This is significantly smaller than
predicted by theoretical models and suggests that major dry mergers do not
contribute to the formation of the red sequence at .Comment: 8 pages emulateapj style, 3 figures, accepted by AJ (March 2010
The Two-Point Correlation of 2QZ Quasars and 2SLAQ LRGs: From a Quasar Fueling Perspective
Public data from the 2dF quasar survey (2QZ) and 2dF/SDSS LRG & QSO (2SLAQ),
with their vast reservoirs of spectroscopically located and identified sources,
afford us the chance to more accurately study their real space correlations in
the hopes of identifying the physical processes that trigger quasar activity.
We have used these two public databases to measure the projected cross
correlation, , between quasars and luminous red galaxies. We find the
projected two-point correlation to have a fitted clustering radius of and a slope, on scales from
0.7-27Mpc.
We attempt to understand this strong correlation by separating the LRG sample
into 2 populations of blue and red galaxies. We measure at the cross
correlation with each population. We find that these quasars have a stronger
correlation amplitude with the bluer, more recently starforming population in
our sample than the redder passively evolving population, which has a
correlation that is much more noisy and seems to flatten on scales Mpc. We compare this result to published work on hierarchical models.
The stronger correlation of bright quasars with LRGs that have undergone a
recent burst of starformation suggests that the physical mechanisms that
produce both activities are related and that minor mergers or tidal effects may
be important triggers of bright quasar activity and/or that bright quasars are
less highly biased than faint quasars.Comment: Accepted for publication in Ap
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