Página 13 dos resultados de 3305 itens digitais encontrados em 0.013 segundos

## Streaming algorithms for recognizing nearly well-parenthesized expressions

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 01/06/2012

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We study the streaming complexity of the membership problem of 1-turn-Dyck2
and Dyck2 when there are a few errors in the input string.
1-turn-Dyck2 with errors: We prove that there exists a randomized one-pass
algorithm that given x checks whether there exists a string x' in 1-turn-Dyck2
such that x is obtained by flipping at most $k$ locations of x' using:
- O(k log n) space, O(k log n) randomness, and poly(k log n) time per item
and with error at most 1/poly(n). - O(k^{1+epsilon} + log n) space for every 0
<= epsilon <= 1, O(log n) randomness, O(polylog(n) + poly(k)) time per item,
with error at most 1/8.
Here, we also prove that any randomized one-pass algorithm that makes error
at most k/n requires at least Omega(k log(n/k)) space to accept strings which
are exactly k-away from strings in 1-turn-Dyck2 and to reject strings which are
exactly (k+2)-away from strings in 1-turn-Dyck2. Since 1-turn-Dyck2 and the
Hamming Distance problem are closely related we also obtain new upper and lower
bounds for this problem.
Dyck2 with errors: We prove that there exists a randomized one-pass algorithm
that given x checks whether there exists a string x' in Dyck2 such that x is
obtained from x' by changing (in some restricted manner) at most k positions
using:
- O(k log n + sqrt(n log n)) space...

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## The error-floor of LDPC codes in the Laplacian channel

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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We analyze the performance of Low-Density-Parity-Check codes in the
error-floor domain where the Signal-to-Noise-Ratio, s, is large, s >> 1. We
describe how the instanton method of theoretical physics, recently adapted to
coding theory, solves the problem of characterizing the error-floor domain in
the Laplacian channel. An example of the (155,64,20) LDPC code with four
iterations (each iteration consisting of two semi-steps: from bits-to-checks
and from checks-to-bits) of the min-sum decoding is discussed. A generalized
computational tree analysis is devised to explain the rational structure of the
leading instantons. The asymptotic for the symbol Bit-Error-Rate in the
error-floor domain is comprised of individual instanton contributions, each
estimated as ~ \exp(-l_{inst;L} s), where the effective distances, l_{inst;L},
of the the leading instantons are 7.6, 8.0 and 8.0 respectively. (The Hamming
distance of the code is 20.) The analysis shows that the instantons are
distinctly different from the ones found for the same coding/decoding scheme
performing over the Gaussian channel. We validate instanton results against
direct simulations and offer an explanation for remarkable performance of the
instanton approximation not only in the extremal...

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## Finding Tizen security bugs through whole-system static analysis

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 22/04/2015

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Tizen is a new Linux-based open source platform for consumer devices
including smartphones, televisions, vehicles, and wearables. While Tizen
provides kernel-level mandatory policy enforcement, it has a large collection
of libraries, implemented in a mix of C and C++, which make their own security
checks. In this research, we describe the design and engineering of a static
analysis engine which drives a full information flow analysis for apps and a
control flow analysis for the full library stack. We implemented these static
analyses as extensions to LLVM, requiring us to improve LLVM's native analysis
features to get greater precision and scalability, including knotty issues like
the coexistence of C++ inheritance with C function pointer use. With our tools,
we found several unexpected behaviors in the Tizen system, including paths
through the system libraries that did not have inline security checks. We show
how our tools can help the Tizen app store to verify important app properties
as well as helping the Tizen development process avoid the accidental
introduction of subtle vulnerabilities.

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## A qutrit Quantum Key Distribution protocol with better noise resistance

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 16/04/2014

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The Ekert quantum key distribution protocol uses pairs of entangled qubits
and performs checks based on a Bell inequality to detect eavesdropping. The
3DEB protocol uses instead pairs of entangled qutrits to achieve better noise
resistance than the Ekert protocol. It performs checks based on a Bell
inequality for qutrits named CHSH-3. In this paper, we present a new protocol,
which also uses pairs of entangled qutrits, but achieves even better noise
resistance than 3DEB. This gain of performance is obtained by using another
inequality called here hCHSH-3. As the hCHSH3 inequality involve products of
observables which become incompatible when using quantum states, we show how
the parties running the protocol can measure the violation of hCHSH3 in the
presence of noise, to ensure the secrecy of the key.; Comment: 11 pages

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## HD 50844: the new look of Delta Sct stars from CoRoT space photometry

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 15/06/2009

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It has also been suggested that the detection of a wealth of very low
amplitude modes in Delta Sct stars was only a matter of signal--to--noise
ratio. Access to this treasure, impossible from the ground, is one of the
scientific aims of the space mission CoRoT, a space mission developed and
operated by CNES. This work presents the results obtained on HD 50844: the
140,016 datapoints were analysed using independent approaches and several
checks performed. A level of 10^{-5} mag was reached in the amplitude spectra
of the CoRoT timeseries. The frequency analysis of the CoRoT timeseries
revealed hundreds of terms in the frequency range 0--30 d^{-1}. All the
cross--checks confirmed this new result. The initial guess that Delta Sct stars
have a very rich frequency content is confirmed. The spectroscopic mode
identification gives theoretical support since very high--degree modes (up to
ell=14) are identified. We also prove that cancellation effects are not
sufficient in removing the flux variations associated to these modes at the
noise level of the CoRoT measurements. The ground--based observations indicate
that HD 50844 is an evolved star that is slightly underabundant in heavy
elements, located on the Terminal Age Main Sequence. Probably due to this
unfavourable evolutionary status...

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## Simple and Effective Type Check Removal through Lazy Basic Block Versioning

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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Dynamically typed programming languages such as JavaScript and Python defer
type checking to run time. In order to maximize performance, dynamic language
VM implementations must attempt to eliminate redundant dynamic type checks.
However, type inference analyses are often costly and involve tradeoffs between
compilation time and resulting precision. This has lead to the creation of
increasingly complex multi-tiered VM architectures.
This paper introduces lazy basic block versioning, a simple JIT compilation
technique which effectively removes redundant type checks from critical code
paths. This novel approach lazily generates type-specialized versions of basic
blocks on-the-fly while propagating context-dependent type information. This
does not require the use of costly program analyses, is not restricted by the
precision limitations of traditional type analyses and avoids the
implementation complexity of speculative optimization techniques.
We have implemented intraprocedural lazy basic block versioning in a
JavaScript JIT compiler. This approach is compared with a classical flow-based
type analysis. Lazy basic block versioning performs as well or better on all
benchmarks. On average, 71% of type tests are eliminated, yielding speedups of
up to 50%. We also show that our implementation generates more efficient
machine code than TraceMonkey...

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## An introduction to Gravitational Lensing in TeVeS gravity

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 27/11/2006

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Bekenstein's (2004) TeVeS theory has added an interesting twist to the search
for dark matter and dark energy, modifying the landscape of gravity-related
astronomy day by day. Built bottom-up rather than top-down as most gravity
theories, TeVeS-like theories are healthily rooted on empirical facts, hence
immediately passing sanity checks on galaxy rotation curves, solar system
constraints, even bullet cluster of galaxies and cosmology with the help of 2eV
neutrinos. Nonetheless, empirical checks are far from perfect and complete, and
groups of different expertises are rapidly increasing the number of falsifiable
properties of the theory. The theory has also been made much simpler and more
general thanks to the work of Zlosnik, Ferreira, Starkman (gr-qc/0606039,
astro-ph/0607411). Here I attempt a tutorial of how to compute lensing
convergence, time delays etc in TeVeS-like theories for non-spherical lenses. I
gave examples to illustrate a few common caveats of Dark-Matter-guided
intuitions.; Comment: 7p, Lecture notes for Sicily Gravitational Lensing School, Oct 29-Nov
3. Comments Welcome

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## Form factors in the SS model and its RSOS restrictions

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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New integral representations for form factors in the two parametric SS model
are proposed. Some form factors in the parafermionic sine-Gordon model and in
an integrable perturbation of SU(2) coset conformal field theories are
straightforwardly obtained by different quantum group restrictions. Numerical
checks on the value of the central charge are performed.; Comment: 16 pages, 5 tables; v2:misprints corrected, clearer notations,
discussion extended; v4: formula for the SS trace operator corrected,
additional numerical checks on the central charge, proposal for p-function of
exponential fields now coherent with the trace, submitted to NPB. v5:table 1
added, references added, diverse comments including Comment on the energy of
the vacuum added

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## The Edinburgh/Durham Southern Galaxy Catalogue - IX. The Galaxy Catalogue

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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We announce here the public availability of the Edinburgh/Durham Southern
Galaxy Catalogue (EDSGC, http://www.edsgc.org). This objective galaxy catalogue
was constructed using the COSMOS micro-densitometer at the Royal Observatory
Edinburgh and constitutes one of the largest digitized galaxy surveys currently
in existence. The EDSGC contains a total of 1,495,877 galaxies (each with 27
image parameters) covering an contiguous area of 1182 sq deg centered on the
South Galactic Pole. The data consists of photographic bj magnitudes calibrated
via CCD sequences which provide a plate-to-plate accuracy of bj~0.1. Extensive
external checks have demonstrated that the global EDSGC photometry is free of
large-scale systematic gradients and is therefore, ideal for studying the
distribution of galaxies on large angular scales. Independent spectroscopy of
EDSGC galaxies has shown that the accuracy of the star-galaxy separation is
consistent with earlier visual checks and that only 12% of EDSGC galaxies are
potentially mis-classified. This paper is intended to provide a summary of the
essential details of the catalogue's design and construction as well as provide
a brief summary of the main scientific achievements using the EDSGC over the
last ten years.; Comment: Paper only published here on astro-ph. Paper is still valid and
describes the EDSGC. The data is available from the authors upon request...

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## IUPC: Identification and Unification of Process Constraints

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 18/04/2011

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Business Process Compliance (BPC) has gained significant momentum in research
and practice during the last years. Although many approaches address BPC, they
mostly assume the existence of some kind of unified base of process constraints
and focus on their verification over the business processes. However, it
remains unclear how such an inte- grated process constraint base can be built
up, even though this con- stitutes the essential prerequisite for all further
compliance checks. In addition, the heterogeneity of process constraints has
been neglected so far. Without identification and separation of process
constraints from domain rules as well as unification of process constraints,
the success- ful IT support of BPC will not be possible. In this technical
report we introduce a unified representation framework that enables the
identifica- tion of process constraints from domain rules and their later
unification within a process constraint base. Separating process constraints
from domain rules can lead to significant reduction of compliance checking
effort. Unification enables consistency checks and optimizations as well as
maintenance and evolution of the constraint base on the other side.; Comment: 13 pages, 4 figures, technical report

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## Detection of Configuration Vulnerabilities in Distributed (Web) Environments

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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Many tools and libraries are readily available to build and operate
distributed Web applications. While the setup of operational environments is
comparatively easy, practice shows that their continuous secure operation is
more difficult to achieve, many times resulting in vulnerable systems exposed
to the Internet. Authenticated vulnerability scanners and validation tools
represent a means to detect security vulnerabilities caused by missing patches
or misconfiguration, but current approaches center much around the concepts of
hosts and operating systems. This paper presents a language and an approach for
the declarative specification and execution of machine-readable security checks
for sets of more fine-granular system components depending on each other in a
distributed environment. Such a language, building on existing standards,
fosters the creation and sharing of security content among security
stakeholders. Our approach is exemplified by vulnerabilities of and
corresponding checks for Open Source Software commonly used in today's Internet
applications.; Comment: 18 pages. To appear in Proc. of Security and Privacy in Communication
Networks - 8th Iternational ICST Conference, SecureComm, 2012

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## Separability and entanglement in 2x2xN composite quantum systems

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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We investigate separability and entanglement of mixed states in ${\cal
C}^2\otimes{\cal C}^2\otimes{\cal C}^N$ three party quantum systems. We show
that all states with positive partial transposes that have rank $\le N$ are
separable. For the 3 qubit case (N=2) we prove that all states $\rho$ that have
positive partial transposes and rank 3 are separable. We provide also
constructive separability checks for the states $\rho$ that have the sum of the
rank of $\rho$ and the ranks of partial transposes with respect to all
subsystems smaller than 15N-1.; Comment: Finally corrected file submitted. Numerous misprints and small errors
corrected, better versions of constructive separability checks included,
updated and extended references

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## Conformal perturbation theory and higher spin entanglement entropy on the torus

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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We study the free fermion theory in 1+1 dimensions deformed by chemical
potentials for holomorphic, conserved currents at finite temperature and on a
spatial circle. For a spin-three chemical potential \mu, the deformation is
related at high temperatures to a higher spin black hole in hs[0] theory on
AdS_3 spacetime. We calculate the order \mu^2 corrections to the single
interval Renyi and entanglement entropies on the torus using the bosonized
formulation. A consistent result, satisfying all checks, emerges upon carefully
accounting for both perturbative and winding mode contributions in the
bosonized language. The order \mu^2 corrections involve integrals that are
finite but potentially sensitive to contact term singularities. We propose and
apply a prescription for defining such integrals which matches the Hamiltonian
picture and passes several non-trivial checks for both thermal corrections and
the Renyi entropies at this order. The thermal corrections are given by a
weight six quasi-modular form, whilst the Renyi entropies are controlled by
quasi-elliptic functions of the interval length with modular weight six. We
also point out the well known connection between the perturbative expansion of
the partition function in powers of the spin-three chemical potential and the
Gross-Taylor genus expansion of large-N Yang-Mills theory on the torus. We note
the absence of winding mode contributions in this connection...

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## S-duality in N=2 supersymmetric gauge theories

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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A solution to the infinite coupling problem for N=2 conformal supersymmetric
gauge theories in four dimensions is presented. The infinitely-coupled theories
are argued to be interacting superconformal field theories (SCFTs) with weakly
gauged flavor groups. Consistency checks of this proposal are found by
examining some low-rank examples. As part of these checks, we show how to
compute new exact quantities in these SCFTs: the central charges of their
flavor current algebras. Also, the isolated rank 1 E_6 and E_7 SCFTs are found
as limits of Lagrangian field theories.; Comment: 25 pages, 3 figures. v3: error in appendix A corrected, reference
removed

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## Modified Binary Search Algorithm

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 06/06/2014

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This paper proposes a modification to the traditional binary search algorithm
in which it checks the presence of the input element with the middle element of
the given set of elements at each iteration. Modified binary search algorithm
optimizes the worst case of the binary search algorithm by comparing the input
element with the first & last element of the data set along with the middle
element and also checks the input number belongs to the range of numbers
present in the given data set at each iteration there by reducing the time
taken by the worst cases of binary search algorithm.

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## Pseudo-codeword Landscape

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Relevância na Pesquisa

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We discuss the performance of Low-Density-Parity-Check (LDPC) codes decoded
by means of Linear Programming (LP) at moderate and large
Signal-to-Noise-Ratios (SNR). Utilizing a combination of the previously
introduced pseudo-codeword-search method and a new "dendro" trick, which allows
us to reduce the complexity of the LP decoding, we analyze the dependence of
the Frame-Error-Rate (FER) on the SNR. Under Maximum-A-Posteriori (MAP)
decoding the dendro-code, having only checks with connectivity degree three,
performs identically to its original code with high-connectivity checks. For a
number of popular LDPC codes performing over the Additive-White-Gaussian-Noise
(AWGN) channel we found that either an error-floor sets at a relatively low
SNR, or otherwise a transient asymptote, characterized by a faster decay of FER
with the SNR increase, precedes the error-floor asymptote. We explain these
regimes in terms of the pseudo-codeword spectra of the codes.; Comment: 5 pages, 2 figures, proceedings of ISIT '07

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## Predicate Abstraction with Under-approximation Refinement

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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We propose an abstraction-based model checking method which relies on
refinement of an under-approximation of the feasible behaviors of the system
under analysis. The method preserves errors to safety properties, since all
analyzed behaviors are feasible by definition. The method does not require an
abstract transition relation to be generated, but instead executes the concrete
transitions while storing abstract versions of the concrete states, as
specified by a set of abstraction predicates. For each explored transition the
method checks, with the help of a theorem prover, whether there is any loss of
precision introduced by abstraction. The results of these checks are used to
decide termination or to refine the abstraction by generating new abstraction
predicates. If the (possibly infinite) concrete system under analysis has a
finite bisimulation quotient, then the method is guaranteed to eventually
explore an equivalent finite bisimilar structure. We illustrate the application
of the approach for checking concurrent programs.; Comment: 22 pages, 3 figures, accepted for publication in Logical Methods in
Computer Science journal (special issue CAV 2005)

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## A Quantum Key Distribution Protocol for qudits with better noise resistance

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 30/04/2015

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The Ekert quantum key distribution protocol uses pairs of entangled qubits
and performs checks based on a Bell inequality to detect eavesdropping. The
N-DEB protocol uses instead pairs of entangled qudits to achieve better noise
resistance than the Ekert protocol. It performs checks based on the Bell CGLMP
inequality for qudits. In this paper, we present the generalization for qudits
of our protocol h3DEB (for qutrits). This protocol also uses pairs of entangled
qudits, but achieves even better noise resistance than N-DEB and is showed to
be secure against the same family of cloning attacks than N-DEB. This gain of
performance is obtained by using another inequality called here hCHSH-$d$. For
each party, the hCHSH-$d$ inequality involves $2d$ observables. We explain how
the parties can measure these observables and thus are able to check the
violation of hCHSH-$d$. In the presence of noise, this violation allows the
parties to ensure the secrecy of the key because it guarantees the absence of a
local Trojan horse attack. The advantage of our proposed scheme is that it
results in an increased resistance to noise while remaining secure against
individual attacks.; Comment: arXiv admin note: substantial text overlap with arXiv:1404.4199

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## Full one-loop electroweak radiative corrections to single Higgs production in e+ e-

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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We present the full ${{\cal O}}(\alpha)$ electroweak radiative corrections to
single Higgs production in \epemt. This takes into account the full one-loop
corrections as well as the effects of hard photon radiation. We include both
the fusion and Higgs-strahlung processes. The computation is performed with the
help of {\tt GRACE-loop} where we have implemented a generalised non-linear
gauge fixing condition. The latter includes 5 gauge parameters that can be used
for checks on our results. Besides the UV, IR finiteness and gauge parameter
independence checks it proves also powerful to test our implementation of the
5-point function. We find that for a 500GeV machine and a light Higgs of mass
150GeV, the total ${{\cal O}}(\alpha)$ correction is small when the results are
expressed in terms of $\alpha_{{\rm QED}}$. The total correction decreases
slightly for higher energies. For moderate centre of mass energies the total
${{\cal O}}(\alpha)$ decreases as the Higgs mass increases, reaching -10% for
$M_H=350$GeV and $\sqrt{s}=500$GeV. In order to quantify the genuine weak
corrections we have subtracted the universal virtual and bremsstrahlung
correction from the full ${{\cal O}}(\alpha)$. We find, for $M_H=150$GeV, a
weak correction slowly decreasing from -2% to -4% as the energy increases from
$\sqrt{s}=300$GeV to $\sqrt{s}=1$TeV after expressing the tree-level results in
terms of $G_\mu$; Comment: 16 pages...

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## Bonus Symmetry and the Operator Product Expansion of N=4 Super-Yang-Mills

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 03/05/1999

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The superconformal group of N=4 super-Yang-Mills has two types of operator
representations: short and long. We conjecture that operator product expansions
for which at least two of the three operators are short exactly respect a bonus
U(1)_Y R-symmetry, which acts as an automorphism of the superconformal group.
This conjecture is for arbitrary gauge group G and gauge coupling g_{YM}. A
consequence is that n\leq 4-point functions involving only short operators
exactly respect the U(1)_Y symmetry, as has been previously conjectured based
on AdS duality. This, in turn, would imply that all n\leq 3 -point functions
involving only short operators are not renormalized, as has also been
previously conjectured and subjected to perturbative checks. It is argued that
instantons are compatible with our conjecture. Some perturbative checks of the
conjecture are presented and SL(2,Z) modular transformation properties are
discussed.; Comment: 22 pages, 2 figures, harvmac

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