3,622 research outputs found
New Recursion Relations and a Flat Space Limit for AdS/CFT Correlators
We consider correlation functions of the stress-tensor or a conserved current
in AdS_{d+1}/CFT_d computed using the Hilbert or the Yang-Mills action in the
bulk. We introduce new recursion relations to compute these correlators at tree
level. These relations have an advantage over the BCFW-like relations described
in arXiv:1102.4724 and arXiv:1011.0780 because they can be used in all
dimensions including d=3. We also introduce a new method of extracting
flat-space S-matrix elements from AdS/CFT correlators in momentum space. We
show that the (d+1)-dimensional flat-space amplitude of gravitons or gluons can
be obtained as the coefficient of a particular singularity of the d-dimensional
correlator of the stress-tensor or a conserved current; this technique is valid
even at loop-level in the bulk. Finally, we show that our recursion relations
automatically generate correlators that are consistent with this observation:
they have the expected singularity and the flat-space gluon or graviton
amplitude appears as its coefficient.Comment: 22+6 pages (v2) typos fixe
Lessons from All Logs Summation in Yukawa Theories
Some features of old results in the total summation of all logarithmic
contributions of all diagrams in Yukawa theory are presented. We discuss some
lessons from this picture for the description of Pomeron, odderon, etc. in QCD.Comment: 6 pages, 2 figure
Hrs- and CD63-dependent competing mechanisms make different sized endosomal intraluminal vesicles.
Multivesicular endosomes/bodies (MVBs) contain intraluminal vesicles (ILVs) that bud away from the cytoplasm. Multiple mechanisms of ILV formation have been identified, but the relationship between different populations of ILVs and MVBs remains unclear. Here, we show in HeLa cells that different ILV subpopulations can be distinguished by size. EGF stimulation promotes the formation of large ESCRT-dependent ILVs, whereas depletion of the ESCRT-0 component, Hrs, promotes the formation of a uniformly sized population of small ILVs, the formation of which requires CD63. CD63 has previously been implicated in ESCRT-independent sorting of PMEL in MVBs and transfected PMEL is present on the small ILVs that form on Hrs depletion. Upregulation of CD63-dependent ILV formation by Hrs depletion indicates that Hrs and CD63 regulate competing machineries required for the generation of distinct ILV subpopulations. Taken together our results indicate that ILV size is influenced by their cargo and mechanism of formation and suggest a competitive relationship between ESCRT-dependent and -independent mechanisms of ILV formation within single MVBs
EGF receptor trafficking: consequences for signaling and cancer
The ligand-stimulated epidermal growth factor receptor (EGFR) has been extensively studied in the analysis of molecular mechanisms regulating endocytic traffic and the role of that traffic in signal transduction. Although such studies have largely focused on mitogenic signaling and dysregulated traffic in tumorigenesis, there is growing interest in the potential role of EGFR traffic in cell survival and the consequent response to cancer therapy. Here we review recent advances in our understanding of molecular mechanisms regulating ligand-stimulated EGFR activation, internalization, and post-endocytic sorting. The role of EGFR overexpression/mutation and new modulators of EGFR traffic in cancer and the response to cancer therapeutics are also discussed. Finally, we speculate on the relationship between EGFR traffic and cell survival
Estimated 2020 CO2 Emission Reductions in Virginia’s Transportation Sector from COVID-19
The initial lockdown phase of the COVID-19 pandemic presented an unfortunate opportunity to observe how abrupt, large-scale changes in traffic volume can reduce greenhouse gas emissions. This study explores how carbon dioxide (CO2) emissions from Virginia’s transportation sector may have been affected by the changes in activity stemming from COVID-19 to inform more carbon-neutral policies as the state recovers from the economic downfall. Emission savings were calculated by multiplying the percent change from 2019 to 2020 in traffic volume from the Virginia Department of Transportation with the business-as-usual 2020 U.S. Environmental Protection Agency estimate of CO2 emissions for Virginia’s transportation sector. We estimate Virginia’s 2020 COVID-19 transportation CO2 emissions reduction is around 15.0% (14.2 to 15.7%), with reduced passenger vehicle traffic making up the bulk of the inferred reduction. This study highlights the utility of reimagining our current transportation sector as a way to implement sustainable, state-level carbon reduction policies, such as the Clean Car Standards
Maximally Supersymmetric Planar Yang-Mills Amplitudes at Five Loops
We present an ansatz for the planar five-loop four-point amplitude in
maximally supersymmetric Yang-Mills theory in terms of loop integrals. This
ansatz exploits the recently observed correspondence between integrals with
simple conformal properties and those found in the four-point amplitudes of the
theory through four loops. We explain how to identify all such integrals
systematically. We make use of generalized unitarity in both four and D
dimensions to determine the coefficients of each of these integrals in the
amplitude. Maximal cuts, in which we cut all propagators of a given integral,
are an especially effective means for determining these coefficients. The set
of integrals and coefficients determined here will be useful for computing the
five-loop cusp anomalous dimension of the theory which is of interest for
non-trivial checks of the AdS/CFT duality conjecture. It will also be useful
for checking a conjecture that the amplitudes have an iterative structure
allowing for their all-loop resummation, whose link to a recent string-side
computation by Alday and Maldacena opens a new venue for quantitative AdS/CFT
comparisons.Comment: 52 pages, 20 figures, revte
Twistors, Harmonics and Holomorphic Chern-Simons
We show that the off-shell N=3 action of N=4 super Yang-Mills can be written
as a holomorphic Chern-Simons action whose Dolbeault operator is constructed
from a complex-real (CR) structure of harmonic space. We also show that the
local space-time operators can be written as a Penrose transform on the coset
SU(3)/(U(1) \times U(1)). We observe a strong similarity to ambitwistor space
constructions.Comment: 34 pages, 3 figures, v2: replaced with published version, v3: Added
referenc
Quantized Detector Networks: A review of recent developments
QDN (quantized detector networks) is a description of quantum processes in
which the principal focus is on observers and their apparatus, rather than on
states of SUOs (systems under observation). It is a realization of Heisenberg's
original instrumentalist approach to quantum physics and can deal with time
dependent apparatus, multiple observers and inter-frame physics. QDN is most
naturally expressed in the mathematical language of quantum computation, a
language ideally suited to describe quantum experiments as processes of
information exchange between observers and their apparatus. Examples in quantum
optics are given, showing how the formalism deals with quantum interference,
non-locality and entanglement. Particle decays, relativity and non-linearity in
quantum mechanics are discussed.Comment: 59 pages, 14 figures, to be published in Int. J. Mod. Phys.
AdS/SCFT in Superspace
A discussion of the AdS/CFT correspondence in IIB is given in a superspace
context. The main emphasis is on the properties of SCFT correlators on the
boundary which are studied using harmonic superspace techniques. These
techniques provide the easiest way of implementing the superconformal Ward
identities. The Ward identities, together with analyticity, can be used to give
a compelling argument in support of the non-renormalisation theorems for two-
and three-point functions, and to establish the triviality of extremal and
next-to-extremal correlation functions. The OPE in is also briefly discussed.Comment: 10 pages; talk given by PSH at 2nd Gursey Memorial Conference, June
200
On the Strong Coupling Scaling Dimension of High Spin Operators
We give an exact analytic solution of the strong coupling limit of the
integral equation which was recently proposed to describe the universal scaling
function of high spin operators in N = 4 gauge theory. The solution agrees with
the prediction from string theory, confirms the earlier numerical analysis and
provides a basis for developing a systematic perturbation theory around strong
coupling.Comment: 26 pages, 2 figure
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