17770397
Noncommutative Spacetime and Emergent Gravity
We argue that a field theory defined on noncommutative (NC) spacetime should be regarded as a theory of gravity, which we refer to as the emergent gravity. A whole point of the emergent gravity is essentially originated from the basic property: A NC spacetime is a (NC) phase space. This fact leads to two important consequences: (I) A NC field theory can basically be identified with a matrix model or a large N field theory where NC fields can be regarded as master fields of large N matrices. (II) NC fields essentially define vector (tetrad) fields. So they define a gravitational metric of some manifold as an emergent geometry from NC gauge fields. Of course, the pictures (I) and (II) should refer to the same physics, which should be familiar with the large N duality in string theory. The 1/N corrections in the picture (I) correspond to the derivative corrections in terms of the noncommutativity \theta for the picture (II).
119204681
Emergent Spacetime and The Cosmological Constant
We address issues on the origin of gravity and the dark energy (or the cosmological constant) from the perspectives of emergent gravity. We discuss how the emergent gravity reveals a noble, radically different picture about the origin of spacetime, which is crucial for a tenable solution of the cosmological constant problem. In particular, the emergent gravity naturally explains the dynamical origin of flat spacetime, which is absent in Einstein gravity.
15769713
A Complete Classification of D-branes in Type IIB Plane Wave Background
We give a complete classification of D-branes in the type IIB plane wave background using Green-Schwarz superstring theory. We find all possible supersymmetric oblique and curved D-branes and consider their intersections. The supersymmetries preserved by various configurations of these D-branes are also identified. In particular, we show that D+-branes of type (+,−, n, n) for n = 1, 2, 3, 4 preserve 4 dynamical supersymmetries by introducing gauge field excitations and newly discovered oblique D5and D7-branes also preserve four or two dynamical supersymmetries with gauge field condensates. Furthermore we find new curved D-branes preserving four dynamical supersymmetries.
12060341
ALE spaces from noncommutative U(1) instantons via exact Seiberg-Witten map
The exact Seiberg–Witten (SW) map of a noncommutative (NC) gauge theory gives the commutative equivalent as an ordinary gauge theory coupled to a field dependent effective metric. We study instanton solutions of this commutative equivalent whose self-duality equation turns out to be the exact SW map of NC instantons. We derive general differential equations governing U(1) instantons and we explicitly get an exact solution corresponding to the single NC instanton. Remarkably the effective metric induced by the single U(1) instanton is related to the Eguchi–Hanson metric—the simplest gravitational instanton. Surprisingly the instanton number is not quantized but depends on an integration constant. Our result confirms the expected non-perturbative breakdown of the SW map. However, the breakdown of the map arises in a consistent way: the instanton number plays the role of a parameter giving rise to a one-parameter family of Eguchi–Hanson metrics.
118454134
BRST Cohomology and Its Application to QED
We construct the BRST cohomology under a positive definite inner product and obtain the Hodge decomposition theorem at a non-degenerate state vector space $V$. The harmonic states isomorphic with a BRST cohomology class correspond to the physical Hilbert space with positive norm as long as the completeness of $Q_{BRST}$ is satisfied. We explicitly define ``co-BRST'' operator and analyze the quartet mechanism in QED.
12059305
Superstrings and D-branes in A Plane Wave
We carefully analyze the supersymmetry algebra of closed strings and open strings in a type IIB plane wave background. We use eight component chiral spinors, SO(8) MajoranaWeyl spinors, in light-cone gauge to provide a useful basis of string field theory calculation in the plane wave. We consider the two classes of D-branes, D±-branes, and give a worldsheet derivation of conserved supercurrents for all half BPS D-branes preserving 16 supersymmetries in the type IIB plane wave background. We exhaustively provide the supersymmetry algebra of the half BPS branes as well. We also point out that the supersymmetry algebra distinguishes the two SO(4) directions with relative sign which is consistent with the Z2 symmetry of the string action.
800216
A closed string tachyon vacuum
In bosonic closed string field theory the ``tachyon potential" is a potential for the tachyon, the dilaton, and an infinite set of massive fields. Earlier computations of the potential did not include the dilaton and the critical point formed by the quadratic and cubic interactions was destroyed by the quartic tachyon term. We include the dilaton contributions to the potential and find that a critical point survives and appears to become more shallow. We are led to consider the existence of a closed string tachyon vacuum, a critical point with zero action that represents a state where space-time ceases to be dynamical. Some evidence for this interpretation is found from the study of the coupled metric-dilaton-tachyon effective field equations, which exhibit rolling solutions in which the dilaton runs to strong coupling and the Einstein metric undergoes collapse.
1154617
Stress Tensors in p-adic String Theory and Truncated OSFT
We construct the stress tensors for the p-adic string model and for the pure tachyonic sector of open string field theory by naive metric covariantization of the action. Then we give the concrete energy density of a lump solution of the p-adic model. In the cubic open bosonic string field theory, we also give the energy density of a lump solution and pressure evolution of a rolling tachyon solution.
14942523
Studies of stability and robustness for artificial neural networks and boosted decision trees
In this paper, we compare the performance, stability and robustness of Artificial Neural Networks (ANN) and Boosted Decision Trees (BDT) using MiniBooNE Monte Carlo samples. These methods attempt to classify events given a number of identification variables. The BDT algorithm has been discussed by us in previous publications. Testing is done in this paper by smearing and shifting the input variables of testing samples. Based on these studies, BDT has better particle identification performance than ANN. The degradation of the classifications obtained by shifting or smearing variables of testing results is smaller for BDT than for ANN.
13902096
Dilaton deformations in closed string field theory
The dilaton theorem implies that the contribution to the dilaton potential from cubic interactions of all levels must be cancelled by the elementary quartic self-coupling of dilatons. We use this expectation to test the quartic structure of closed string field theory and to study the rules for level expansion. We explain how to use the results of Moeller to compute quartic interactions of states that, just like the dilaton, are neither primary nor have a simple ghost dependence. Our analysis of cancellations is made richer by discussing simultaneous dilaton and marginal deformations. We find evidence for two facts: as the level is increased quartic interactions become suppressed and closed string field theory may be able to describe arbitrarily large dilaton deformations.
18986664
Discovery Potential of the Standard Model Higgs Boson Through H -> WW Decay Mode with the ATLAS Detector at LHC
We report results of a study of the Standard Model Higgs boson discovery potential through the W-pair leptonic decay modes with the ATLAS detector at LHC at 14 TeV center-of-mass energy. We used MC samples with full detector simulation and reconstruction of the ATLAS experiment to estimate the ATLAS detection sensitivity for the reaction of pp -> H -> WW -> e\nu \mu\nu with no hard jet or two hard jets in the final states. The prospects for the Higgs boson searches at ATLAS are presented, including trigger efficiencies and data-driven methods to estimate the backgrounds using control samples in data. With 10/fb of integrated luminosity, one would expect to discover a Standard Model Higgs boson with ATLAS detector in Higgs boson mass range 135 < m_H < 190 GeV. If the Higgs boson does not exist, we will extend and confirm the exclusion produced by the Tevatron Higgs boson search result, which has ruled out the Higgs boson mass range of 160 < m_H < 170 GeV at 95% confidence level. If Higgs boson would be discovered, ATLAS could measure its mass with a precision of about 2 and 7 GeV for Higgs boson mass around 160 GeV and 130 GeV, respectively.