scholarly journals Four-dimensional gravity on a covariant noncommutative space

2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
G. Manolakos ◽  
P. Manousselis ◽  
G. Zoupanos
Author(s):  
Shoichi Kawamoto ◽  
Koichi Nagasaki ◽  
Wen-Yu Wen

Abstract We consider charged rotating BTZ black holes in noncommutative space using a Chern–Simons theory formulation of $(2+1)$-dimensional gravity. The noncommutativity between the radial and the angular variables is introduced through the Seiberg–Witten map for gauge fields, and the deformed geometry to the first order in the noncommutative parameter is derived. It is found that the deformation also induces nontrivial torsion, and Einstein–Cartan theory appears to be a suitable framework to investigate the equations of motion. Though the deformation is indeed nontrivial, the deformed and the original Einstein equations are found to be related by a rather simple coordinate transformation.


2021 ◽  
pp. 2100085
Author(s):  
G. Manolakos ◽  
P. Manousselis ◽  
G. Zoupanos

2019 ◽  
Vol 19 (2) ◽  
pp. 455-461
Author(s):  
Z Rezaei ◽  
T Alizadeh ◽  
◽  

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Nima Afkhami-Jeddi ◽  
Henry Cohn ◽  
Thomas Hartman ◽  
Amirhossein Tajdini

Abstract We study the torus partition functions of free bosonic CFTs in two dimensions. Integrating over Narain moduli defines an ensemble-averaged free CFT. We calculate the averaged partition function and show that it can be reinterpreted as a sum over topologies in three dimensions. This result leads us to conjecture that an averaged free CFT in two dimensions is holographically dual to an exotic theory of three-dimensional gravity with U(1)c×U(1)c symmetry and a composite boundary graviton. Additionally, for small central charge c, we obtain general constraints on the spectral gap of free CFTs using the spinning modular bootstrap, construct examples of Narain compactifications with a large gap, and find an analytic bootstrap functional corresponding to a single self-dual boson.


2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
A. de Giorgi ◽  
S. Vogl

Abstract The Kaluza-Klein (KK) decomposition of higher-dimensional gravity gives rise to a tower of KK-gravitons in the effective four-dimensional (4D) theory. Such massive spin-2 fields are known to be connected with unitarity issues and easily lead to a breakdown of the effective theory well below the naive scale of the interaction. However, the breakdown of the effective 4D theory is expected to be controlled by the parameters of the 5D theory. Working in a simplified Randall-Sundrum model we study the matrix elements for matter annihilations into massive gravitons. We find that truncating the KK-tower leads to an early breakdown of perturbative unitarity. However, by considering the full tower we obtain a set of sum rules for the couplings between the different KK-fields that restore unitarity up to the scale of the 5D theory. We prove analytically that these are fulfilled in the model under consideration and present numerical tests of their convergence. This work complements earlier studies that focused on graviton self-interactions and yields additional sum rules that are required if matter fields are incorporated into warped extra-dimensions.


2006 ◽  
Vol 73 (12) ◽  
Author(s):  
Nicolas Chatillon ◽  
Cosmin Macesanu ◽  
Aleksandr Pinzul ◽  
Mark Trodden

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