scholarly journals Surface defects from fractional branes. Part II

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
S.K. Ashok ◽  
M. Billò ◽  
M. Frau ◽  
A. Lerda ◽  
S. Mahato
Keyword(s):  
String Theory ◽  
Surface Defect ◽  
Surface Defects ◽  
Closed String ◽  
Brane World ◽  
Type Ii ◽  
Yang Mills ◽  
Background Values ◽  
World Volume ◽  
Set Up

Abstract A generic half-BPS surface defect of $$ \mathcal{N} $$ N = 4 supersymmetric U(N ) Yang- Mills theory is described by a partition of N = n1 + . . . + nM and a set of 4M continuous parameters. We show that such a defect can be realized by nI stacks of fractional D3-branes in Type II B string theory on a ℤM orbifold background in which the brane world-volume is partially extended along the orbifold directions. In this set up we show that the 4M continuous parameters correspond to constant background values of certain twisted closed string scalars of the orbifold. These results extend and generalize what we have presented for the simple defects in a previous paper.

scholarly journals TWO-DIMENSIONAL YANG-MILLS THEORIES ARE STRING THEORIES

1993 ◽  
Vol 08 (23) ◽  
pp. 2223-2235 ◽  
Author(s):  
STEPHEN G. NACULICH ◽  
HAROLD A. RIGGS ◽  
HOWARD J. SCHNITZER
Keyword(s):  
String Theory ◽  
Partition Function ◽  
Arbitrary Number ◽  
Closed String ◽  
Two Dimensional ◽  
Branched Covers ◽  
Yang Mills ◽  
String Worldsheet ◽  
String Theories

We show that two-dimensional SO (N) and Sp (N) Yang-Mills theories without fermions can be interpreted as closed string theories. The terms in the 1/N expansion of the partition function on an orientable or nonorientable manifold ℳ can be associated with maps from a string worldsheet onto ℳ. These maps are unbranched and branched covers of ℳ with an arbitrary number of infinitesimal worldsheet cross-caps mapped to points in ℳ. These string theories differ from SU (N) Yang-Mills string theory in that they involve odd powers of 1/N and require both orientable and nonorientable worldsheets.

scholarly journals From Type II string theory toward BSM/dark sector physics

2016 ◽  
Vol 31 (34) ◽  
pp. 1630050 ◽  
Author(s):  
Gabriele Honecker
Keyword(s):  
String Theory ◽  
Open String ◽  
New Physics ◽  
Closed String ◽  
Type Ii ◽  
Dark Sector ◽  
Four Dimensions ◽  
Brane Model ◽  
Moduli Stabilization ◽  
String Compactifications

Four-dimensional compactifications of string theory provide a controlled set of possible gauge representations accounting for BSM particles and dark sector components. In this review, constraints from perturbative Type II string compactifications in the geometric regime are discussed in detail and then compared to results from heterotic string compactifications and nonperturbative/nongeometric corners. As a prominent example, an open string realization of the QCD axion is presented. The status of deriving the associated low-energy effective action in four dimensions is discussed and open avenues of major phenomenological importance are highlighted. As examples, a mechanism of closed string moduli stabilization by D-brane backreaction as well as one-loop threshold corrections to the gauge couplings and balancing a low string scale [Formula: see text] with unisotropic compact dimensions are discussed together with implications on potential future new physics observations. For illustrative purposes, an explicit example of a globally consistent D6-brane model with MSSM-like spectrum on [Formula: see text] is presented.

scholarly journals INTERPRETING THE M2-BRANE ACTION

2009 ◽  
Vol 24 (10) ◽  
pp. 721-724 ◽  
Author(s):  
SHAMIK BANERJEE ◽  
ASHOKE SEN
Keyword(s):  
Scalar Field ◽  
Azimuthal Angle ◽  
Free Field ◽  
Brane World ◽  
Polar Coordinate System ◽  
Radial Coordinate ◽  
Field Equations ◽  
Yang Mills ◽  
World Volume ◽  
The World

The world-volume theory of multiple M2-branes proposed recently has a free scalar field. For large vev of this scalar field the world-volume action reduces to that of multiple D2-branes with Yang–Mills coupling proportional to the vev. We suggest that the correct interpretation of this scalar field is as the radial position of the M2-brane center of mass in a cylindrical polar coordinate system. Regarding the azimuthal angle as compact we can regard this as a set of coincident D2-branes in type IIA string theory with varying dilaton and metric. We find that the effective world-volume theory on the D2-branes has Yang–Mills coupling proportional to the radial coordinate; furthermore the radial coordinate satisfies free field equations of motion. This agrees with the corresponding results derived from the M2-brane world-volume theory.

scholarly journals T-duality in nonrelativistic open string theory

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Jaume Gomis ◽  
Ziqi Yan ◽  
Matthew Yu
Keyword(s):  
String Theory ◽  
Open String ◽  
Closed String ◽  
Quantization Scheme ◽  
Yang Mills ◽  
Duality Transformations ◽  
Low Energies ◽  
String Spectrum ◽  
String Background ◽  
Noncommutative Open String Theory

Abstract Nonrelativistic open string theory is defined by a worldsheet theory that produces a Galilean invariant string spectrum and is described at low energies by a nonrelativistic Yang-Mills theory [1]. We study T-duality transformations in the path integral for the sigma model that describes nonrelativistic open string theory coupled to an arbitrary closed string background, described by a string Newton-Cartan geometry, Kalb-Ramond, and dilaton field. We prove that T-duality transformations map nonrelativistic open string theory to relativistic and noncommutative open string theory in the discrete light cone quantization (DLCQ), a quantization scheme relevant for Matrix string theory. We also show how the worldvolume dynamics of nonrelativistic open string theory described by the Dirac-Born-Infeld type action found in [1] maps to the Dirac-Born-Infeld actions describing the worldvolume theories of the DLCQ of open string theory and noncommutative open string theory.

scholarly journals Misaligned supersymmetry and open strings

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Niccolò Cribiori ◽  
Susha Parameswaran ◽  
Flavio Tonioni ◽  
Timm Wrase
Keyword(s):  
String Theory ◽  
Energy Levels ◽  
Closed String ◽  
Type Ii ◽  
Open Strings ◽  
String Landscape ◽  
String Theories

Abstract The study of non-supersymmetric string theories is shedding light on an important corner of the string landscape and might ultimately explain why, so far, we did not observe supersymmetry in our universe. We review how misaligned supersymmetry in closed-string theories leads to a cancellation between bosons and fermions even in non-supersymmetric string theories. We then show that the same cancellation takes place for open strings by studying an anti-Dp-brane placed on top of an Op-plane in type II string theory. Misaligned supersymmetry consists in cancellations between bosons and fermions at different energy levels, in such a way that the averaged number of states grows at a rate dominated by a factor $$ {\mathrm{e}}^{C_{\mathrm{e}\mathrm{ff}}\sqrt{n}} $$ e C eff n , with Ceff< Ctot, where Ctot is the inverse Hagedorn temperature. We prove the previously conjectured complete cancellation, i.e. we prove that Ceff = 0, for a vast class of models.

scholarly journals Topological holography: The example of the D2-D4 brane system

2020 ◽  
Vol 9 (2) ◽  
Author(s):  
Nafiz Ishtiaque ◽  
Seyed Faroogh Moosavian ◽  
Yehao Zhou
Keyword(s):  
String Theory ◽  
Topological String ◽  
Closed String ◽  
Simons Theory ◽  
Topological String Theory ◽  
One Dimensional ◽  
Bf Theory ◽  
World Volume ◽  
Chern Simons ◽  
Chern Simons Theory

We propose a toy model for holographic duality. The model is constructed by embedding a stack of NN D2-branes and KK D4-branes (with one dimensional intersection) in a 6d topological string theory. The world-volume theory on the D2-branes (resp. D4-branes) is 2d BF theory (resp. 4D Chern-Simons theory) with \mathrm{GL}_NGLN (resp. \mathrm{GL}_KGLK) gauge group. We propose that in the large NN limit the BF theory on \mathbb{R}^2ℝ2 is dual to the closed string theory on \mathbb{R}^2 \times \mathbb{R}_+ \times S^3ℝ2×ℝ+×S3 with the Chern-Simons defect on \mathbb{R} \times \mathbb{R}_+ \times S^2ℝ×ℝ+×S2. As a check for the duality we compute the operator algebra in the BF theory, along the D2-D4 intersection – the algebra is the Yangian of \mathfrak{gl}_K𝔤𝔩K. We then compute the same algebra, in the guise of a scattering algebra, using Witten diagrams in the Chern-Simons theory. Our computations of the algebras are exact (valid at all loops). Finally, we propose a physical string theory construction of this duality using D3-D5 brane configuration in type IIB – using supersymmetric twist and \OmegaΩ-deformation.

scholarly journals SO(3)×U(1) Isometric Instantons with Non-Abelian Hair in Four-Dimensional String Theory

1997 ◽  
Vol 12 (25) ◽  
pp. 1847-1858
Author(s):  
Adrián R. Lugo
Keyword(s):  
String Theory ◽  
Type Ii ◽  
Dimensional Solution ◽  
Coset Model

We compute the exact effective string vacuum backgrounds of the level k=81/19 SU(2,1)/U(1) coset model. A compact SU(2) isometry present in this seven-dimensional solution allows one to interpret it after compactification as a four-dimensional non-Abelian SU(2) charged instanton with a singular submanifold and an SO(3) × U(1) isometry. The semiclassical backgrounds, solutions of the type II strings, present similar characteristics

scholarly journals X-SDD: A New Benchmark for Hot Rolled Steel Strip Surface Defects Detection

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 706
Author(s):  
Xinglong Feng ◽  
Xianwen Gao ◽  
Ling Luo
Keyword(s):  
Surface Defect ◽  
Surface Defects ◽  
Steel Strip ◽  
Rolled Strip ◽  
Rolled Steel ◽  
Strip Surface ◽  
Hot Rolled Strip ◽  
Hot Rolled ◽  
Hot Rolled Steel ◽  
Detection Of Defects

It is important to accurately classify the defects in hot rolled steel strip since the detection of defects in hot rolled steel strip is closely related to the quality of the final product. The lack of actual hot-rolled strip defect data sets currently limits further research on the classification of hot-rolled strip defects to some extent. In real production, the convolutional neural network (CNN)-based algorithm has some difficulties, for example, the algorithm is not particularly accurate in classifying some uncommon defects. Therefore, further research is needed on how to apply deep learning to the actual detection of defects on the surface of hot rolled steel strip. In this paper, we proposed a hot rolled steel strip defect dataset called Xsteel surface defect dataset (X-SDD) which contains seven typical types of hot rolled strip defects with a total of 1360 defect images. Compared with the six defect types of the commonly used NEU surface defect database (NEU-CLS), our proposed X-SDD contains more types. Then, we adopt the newly proposed RepVGG algorithm and combine it with the spatial attention (SA) mechanism to verify the effect on the X-SDD. Finally, we apply multiple algorithms to test on our proposed X-SDD to provide the corresponding benchmarks. The test results show that our algorithm achieves an accuracy of 95.10% on the testset, which exceeds other comparable algorithms by a large margin. Meanwhile, our algorithm achieves the best results in Macro-Precision, Macro-Recall and Macro-F1-score metrics.

Lightweight detection algorithm for fine-grained surface defects of aerospace seal rings

2021 ◽  
pp. 1-18
Author(s):  
Hui Liu ◽  
Boxia He ◽  
Yong He ◽  
Xiaotian Tao
Keyword(s):  
Feature Extraction ◽  
Defect Detection ◽  
Surface Defect ◽  
Surface Defects ◽  
Detection Algorithm ◽  
Seal Ring ◽  
Fine Grained ◽  
Aerospace Applications ◽  
Surface Defect Detection ◽  
The Mean

The existing seal ring surface defect detection methods for aerospace applications have the problems of low detection efficiency, strong specificity, large fine-grained classification errors, and unstable detection results. Considering these problems, a fine-grained seal ring surface defect detection algorithm for aerospace applications is proposed. Based on analysis of the stacking process of standard convolution, heat maps of original pixels in the receptive field participating in the convolution operation are quantified and generated. According to the generated heat map, the feature extraction optimization method of convolution combinations with different dilation rates is proposed, and an efficient convolution feature extraction network containing three kinds of dilated convolutions is designed. Combined with the O-ring surface defect features, a multiscale defect detection network is designed. Before the head of multiscale classification and position regression, feature fusion tree modules are added to ensure the reuse and compression of the responsive features of different receptive fields on the same scale feature maps. Experimental results show that on the O-rings-3000 testing dataset, the mean condition accuracy of the proposed algorithm reaches 95.10% for 5 types of surface defects of aerospace O-rings. Compared with RefineDet, the mean condition accuracy of the proposed algorithm is only reduced by 1.79%, while the parameters and FLOPs are reduced by 35.29% and 64.90%, respectively. Moreover, the proposed algorithm has good adaptability to image blur and light changes caused by the cutting of imaging hardware, thus saving the cost.

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