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String Universality and Non-Simply-Connected Gauge Groups in 8D
Mirjam Cvetič, Markus Dierigl, Ling Lin, Hao Y. Zhang, 2020, original scientific article

Abstract: We present a consistency condition for 8D N 1 supergravity theories with nontrivial global structure G=Z for the non-Abelian gauge group, based on an anomaly involving the Z 1-form center symmetry. The interplay with other swampland criteria identifies the majority of 8D theories with gauge group G=Z, which have no string theory realization, as inconsistent quantum theories when coupled to gravity. While this condition is equivalent to geometric properties of elliptic K3 surfaces in F-theory compactifications, it constrains the unexplored landscape of gauge groups in other 8D string models.
Keywords: supergravity theories, string theory, 8D string models
Published in DKUM: 16.10.2023; Views: 447; Downloads: 15
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3.
Yukawa hierarchies in global F-theory models
Mirjam Cvetič, Ling Lin, Mingqiang Liu, Hao Y. Zhang, Gianluca Zoccarato, 2020, original scientific article

Abstract: We argue that global F-theory compactifications to four dimensions gener- ally exhibit higher rank Yukawa matrices from multiple geometric contributions known as Yukawa points. The holomorphic couplings furthermore have large hierarchies for generic complex structure moduli. Unlike local considerations, the compact setup realizes these features all through geometry, and requires no instanton corrections. As an example, we consider a concrete toy model with SU(5) x U(1) gauge symmetry. From the geometry, we find two Yukawa points for the 10-25-4 coupling, producing a rank two Yukawa matrix. Our methods allow us to track all complex structure dependencies of the holomorphic couplings and study the ratio numerically. This reveals hierarchies of O(10(5)) and larger on a full-dimensional subspace of the moduli space.
Keywords: F-theory, supersymmetric effective theories
Published in DKUM: 16.10.2023; Views: 176; Downloads: 11
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4.
Gauge group topology of 8D Chaudhuri-Hockney-Lykken vacua
Mirjam Cvetič, Markus Dierigl, Ling Lin, Hao Y. Zhang, 2021, original scientific article

Abstract: Compactifications of the Chaudhuri-Hockney-Lykken (CHL) string to eight dimensions can be characterized by embeddings of root lattices into the rank 12 momentum lattice ΛM, the so-called Mikhailov lattice. Based on these data, we devise a method to determine the global gauge group structure including all Uð1Þ factors. The key observation is that, while the physical states correspond to vectors in the momentum lattice, the gauge group topology is encoded in its dual. Interpreting a nontrivial π1ðGÞ ≡ Z for the non-Abelian gauge group G as having gauged a Z 1-form symmetry, we also prove that all CHL gauge groups are free of a certain anomaly [1] that would obstruct this gauging. We verify this by explicitly computing Z for all 8D CHL vacua with rankðGÞ ¼ 10. Since our method applies also to T2 compactifications of heterotic strings, we further establish a map that determines any CHL gauge group topology from that of a “parent” heterotic model.
Keywords: astrophysics, compactification, string dualities, string and branes, discrete symmetries, symmetries, gauge symmetries
Published in DKUM: 13.10.2023; Views: 340; Downloads: 14
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5.
Higher-form symmetries and their anomalies in M-/F-theory duality
Mirjam Cvetič, Markus Dierigl, Ling Lin, Hao Y. Zhang, 2021, original scientific article

Abstract: We explore higher-form symmetries of M- and F-theory compactified on elliptic fibrations, determined by the topology of their asymptotic boundaries. The underlying geometric structures are shown to be equivalent to known characterizations of the gauge group topology in F-theory via Mordell-Weil torsion and string junctions. We further study dimensional reductions of the 11d Chern-Simons term in the presence of torsional boundary G4-fluxes, which encode background gauge fields of center one-form symmetries in the lower-dimensional effective gauge theory. We find contributions that can be interpreted as ’t Hooft anomalies involving the one-form symmetry which originate from a fractionalization of the instanton number of non-Abelian gauge theories in F-/M-theory compactifications to 8d=7d and 6d=5d.
Keywords: astrophysics, anomalies, compactification, M-theory, string dualities, discrete symmetries, symmetries
Published in DKUM: 13.10.2023; Views: 339; Downloads: 4
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6.
All eight- and nine-dimensional string vacua from junctions
Mirjam Cvetič, Markus Dierigl, Ling Lin, Hao Y. Zhang, 2022, original scientific article

Abstract: String and 5-brane junctions are shown to succinctly classify all known 8D N ¼ 1 string vacua. This requires an extension of the description for ordinary ½p; q-7-branes to consistently include O7þ planes, which then naturally encodes the dynamics of spn gauge algebras, including their p-form center symmetries. Central to this analysis are loop junctions, i.e., strings/5-branes which encircle stacks of 7-branes and O7þs. Loop junctions further signal the appearance of affine symmetries of emergent 9D descriptions at the 8D moduli space’s boundaries. Such limits reproduce all 9D string vacua, including the two disconnected rank (1,1) moduli components.
Keywords: 9D string vacua, 8D string vacua, anomalies, M-theory, Non-Abelian gauge theories, quantum gravity, string dualities, strings & branes, supergravity, Gauge symmetries
Published in DKUM: 22.09.2023; Views: 210; Downloads: 16
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A simplified method to analyze pile-supported and geosynthetic-reinforced embankments and the influence significance analysis of the design parameters
Liu Feicheng, Zhang Jianjing, Yan Shijie, Cao Licong, 2018, original scientific article

Abstract: A simplified method for evaluating a pile-supported embankment reinforced with geosynthetic (PGRS embankment) is proposed in this paper. The method takes into account not only the arching effect, the membrane effect of the deflected geosynthetic, and the subsoil reaction, but also the pile head settlement, which makes the method applicable for floating piles, as well as piles seated on a firm soil layer. The settlement of the subsoil surface is considered to consist of two parts: (a) the settlement of the subsoil surface equals that of the pile cap with no deformation in geosynthetic yet; (b) the subsoil surface subsides along with the geosynthetic deforming, and the deflected geosynthetic being considered as catenary shaped. The formula for the maximum differential settlement between the subsoil surface and the piles is worked out by analyzing the force equilibrium of the geosynthetic and the stress-strain relationship of the geosynthetic at the edge of the pile cap. The comparison of the calculated results with the observed data and the six current analytical methods has been implemented to verify the proposed method. The influence of the tensile stiffness of the geosynthetic, compression modulus of soft soil, soft soil thickness, embankment height, internal friction angle of the embankment fill and the pile spacing on the subsoil reaction, the stress concentration ratio (SCR) and the tension of the geosynthetic are investigated using the proposed method. The influence significance of these factors has been investigated using the evaluation theory of binary variance analysis for the non-repeatability tests, which helps optimize the design of the PGRS embankment.
Keywords: pile-supported embankment, geosynthetic, simplified method, influence significance, binary variance analysis
Published in DKUM: 11.10.2018; Views: 1327; Downloads: 482
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10.
A simplified approach to estimating the soil stress distribution due to a single pile
Ping Li, Tao Yu, Dongdong Zhang, 2017, original scientific article

Abstract: This paper reports a simplified analytical solution for estimating the soil stress distribution due to pile dependence on the pile dimensions. The exponentially increasing ultimate skin friction along the pile shaft is derived by means of an equilibrium analysis of the soil element around the pile. The soil stress distribution due to the exponentially increasing skin friction and uniformly distributed end bearing of the piles is proposed. The estimated soil stresses are compared using the original Geddes solution, which validates the derivation and formulae obtained.
Keywords: analytical solution, soil stress distribution, skin friction, end bearing
Published in DKUM: 18.06.2018; Views: 1932; Downloads: 81
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