Preprints 2024 Charged Nariai black holes on the dark bubble <p>Authors: Ulf Danielsson and Vincent Van Hemelryck</p> <p>Preprint number: UUITP-13/24</p> <p>Abstract:&nbsp;In this paper, we realise the charged Nariai black hole on a braneworld from a nucleated bubble in AdS&#36;_5&#36;, known as the dark bubble model.<br /> Geometrically, the black hole takes the form of a cylindrical spacetime pulling on the dark bubble. This is realised by a brane embedding in an AdS&#36;_5&#36; black string background. Identifying the brane with a D3-brane in string theory allows us to determine a relation between the fine structure constant and the string coupling, &#36;\alpha_\text{EM} = \frac{3}{2} g_s&#36;, which was previously obtained for a microscopic black hole. We also speculate on the consequences for the Festina Lente bound and neutrino masses.</p> Tue, 21 May 2024 14:16:00 GMT 2024-05-21T14:16:00Z Exploring Black Hole Mimickers:\\Electromagnetic and Gravitational Signatures of AdS Black Shells <p>Authors: Suvendu Giri, Ulf Danielsson, Luis Lehner, Frans Pretorius</p> <p>Preprint number: UUITP-12/24</p> <p>Abstract: We study electromagnetic and gravitational properties of AdS black shells (also referred to as AdS black bubbles)---a class of quantum gravity motivated black hole mimickers, that in the classical limit are described as ultra compact shells of matter. We find that their electromagnetic properties are remarkably similar to black holes. We then discuss the extent to which these objects are distinguishable from black holes, both for its intrinsic interest within the black shell model, but also as a guide for similar efforts in other sub-classes of ECOs. We study photon rings and lensing band characteristics, relevant for very large baseline inteferometry (VLBI) experiments, as well as gravitational wave observables---quasinormal modes in the eikonal limit and the static tidal Love number for non-spinning shells---relevant for ongoing and upcoming gravitational wave experiments.</p> Mon, 06 May 2024 08:35:00 GMT 2024-05-06T08:35:00Z Gauge-Invariant Magnetic Charges in Linearised Gravity <p>Authors: Chris Hull, Maxwell L. Hutt, Ulf Lindstr&ouml;m</p> <p>Preprint number: UUITP-11/24</p> <p>Abstract:&nbsp;Linearised gravity has magnetic charges carried by (linearised) Kaluza-Klein monopoles. A gauge-invariant expression is found for these charges that is similar to Penrose's gauge-invariant expression for the ADM charges. A systematic search is made for other gauge-invariant charges.</p> Fri, 03 May 2024 08:08:00 GMT 2024-05-03T08:08:00Z Super Yang-Mills on Branched Covers and Weighted Projective Spaces <p>Authors: Roman Mauch and Lorenzo Ruggeri</p> <p>Preprint number: UUITP-10/24</p> <p>Abstract:&nbsp;In this work we conjecture the Coulomb branch partition function, including<br /> flux and instanton contributions, for the N = 2 vector multiplet on weighted projective<br /> space CP2N for equivariant Donaldson-Witten and &ldquo;Pestun-like&rdquo; theories. More precisely,<br /> we claim that this partition function agrees with the one computed on a certain branched<br /> cover of CP2 upon matching conical deficit angles with corresponding branch indices. Our<br /> conjecture is substantiated by checking that similar partition functions on spindles agree<br /> with their equivalent on certain branched covers of CP1. We compute the one-loop deter-<br /> minant on the branched cover of CP2 for all flux sectors via dimensional reduction from<br /> the N = 1 vector multiplet on a branched five-sphere along a free S1-action. Our work<br /> paves the way for obtaining partition functions on more generic symplectic toric orbifolds.</p> Wed, 17 Apr 2024 09:56:00 GMT 2024-04-17T09:56:00Z Non-holomorphic modular forms from zeta generators <p>Authors: Daniele Dorigoni, Mehregan Doroudiani, Joshua Drewitt, Martijn Hidding, Axel Kleinschmidt, Oliver Schlotterer, Leila Schneps and Bram Verbeek</p> <p><br /> Preprint number: UUITP-09/24</p> <p>Abstract: We study non-holomorphic modular forms built from iterated integrals of holomorphic modular forms for &#36;\SLtwoZ&#36; known as equivariant iterated Eisenstein integrals. A special subclass of them furnishes an equivalent description of the modular graph forms appearing in the low-energy expansion of string amplitudes at genus one. Notably the Fourier expansion of modular graph forms contains single-valued multiple zeta values. We deduce the appearance of products and higher-depth instances of multiple zeta values in equivariant iterated Eisenstein integrals, and ultimately modular graph forms, from the coefficients of simpler odd Riemann zeta values. This analysis relies on so-called zeta generators which act on certain non-commutative variables in the generating series of the iterated integrals. From an extension of these non-commutative variables we incorporate iterated integrals involving holomorphic cusp forms into our setup and use them to construct the modular completion of triple Eisenstein integrals. Our work represents a fully explicit realisation of the modular graph forms within Brown's framework of equivariant iterated Eisenstein integrals and reveals structural analogies between single-valued period functions appearing in genus zero and one string amplitudes.</p> Thu, 29 Feb 2024 12:54:00 GMT 2024-02-29T12:54:00Z Effective interactions of the open bosonic string via field theory <div> <div> <div> <p>Authors: Lucia M. Garozzo, Alfredo Guevara</p> <p>Preprint number: UUITP-08/24</p> <p>Abstract: We describe a method to extract an effective Lagrangian description for open bosonic strings, at zero transcendentality. The method relies on a particular formulation of its scattering amplitudes derived from color-kinematics duality. More precisely, starting from a (DF)^2 + YM quantum field theory, we integrate out all the massive degrees of freedom to generate an expansion in the inverse string tension &alpha;&prime;. We explicitly compute the Lagrangian terms through O(&alpha;&prime;^4), and target the sector of operators proportional to F^4 to all orders in &alpha;&prime;.</p> </div> </div> </div> Tue, 27 Feb 2024 21:10:00 GMT 2024-02-27T21:10:00Z T-duality between 6d (2,0) and (1,1) Little String Theories with Twist <p>Authors:&nbsp;Hee-Cheol Kim, Kimyeong Lee, Kaiwen Sun, Xin Wang</p> <p>Preprint number: UUITP-07/24</p> Wed, 07 Feb 2024 08:19:00 GMT 2024-02-07T08:19:00Z On Intermediate Exceptional Series <p>Authors: Kimyeong Lee, Kaiwen Sun, Haowu Wang</p> <p>Preprint number: UUITP-06/24</p> <p>Abstract:&nbsp;The Freudenthal--Tits magic square&nbsp;m(A<sub>1</sub>,A<sub>2</sub>)&nbsp;for&nbsp;A=R,C,H,O&nbsp;of semi-simple Lie algebras can be extended by including the sextonions&nbsp;S. A series of non-reductive Lie algebras naturally appear in the new row associated with the sextonions, which we will call the&nbsp;<em>intermediate exceptional series</em>, with the largest one as the intermediate Lie algebra&nbsp;E<sub>7+1/2</sub>&nbsp;constructed by Landsberg--Manivel. We study various aspects of the intermediate vertex operator (super)algebras associated with the intermediate exceptional series, including rationality, coset constructions, irreducible modules, (super)characters and modular linear differential equations. For all&nbsp;g<sub>I</sub>&nbsp;belonging to the intermediate exceptional series, the intermediate VOA&nbsp;L<sub>1</sub>(g<sub>I</sub>)&nbsp;has characters of irreducible modules coinciding with those of the simple rational&nbsp;C<sub>2</sub>-cofinite&nbsp;W-algebra&nbsp;W<sub>-h<sup>&or;</sup>/6</sub>(g,f<sub>&theta;</sub>)&nbsp;studied by Kawasetsu, with&nbsp;g&nbsp;belonging to the Cvitanović--Deligne exceptional series. We propose some new intermediate VOA&nbsp;L<sub>k</sub>(g<sub>I</sub>)&nbsp;with integer level&nbsp;k&nbsp;and investigate their properties. For example, for the intermediate Lie algebra&nbsp;D<sub>6+1/2</sub>&nbsp;between&nbsp;D<sub>6</sub>and&nbsp;E<sub>7</sub>&nbsp;in the subexceptional series and also in Vogel's projective plane, we find that the intermediate VOA&nbsp;L<sub>2</sub>(D<sub>6+1/2</sub>)&nbsp;has a simple current extension to a SVOA with four irreducible Neveu--Schwarz modules. We also provide some (super) coset constructions such as&nbsp;L<sub>2</sub>(E<sub>7</sub>)/L<sub>2</sub>(D<sub>6+1/2</sub>)&nbsp;and&nbsp;L<sub>1</sub>(D<sub>6+1/2</sub>)<sup>&otimes;2</sup>\!/L<sub>2</sub>(D<sub>6+1/2</sub>). In the end, we find that the theta blocks associated with the intermediate exceptional series produce some new holomorphic Jacobi forms of critical weight and lattice index.</p> Wed, 07 Feb 2024 08:11:00 GMT 2024-02-07T08:11:00Z N=(2,2) superfields and geometry revisited <p>Authors: Chris Hull and Maxim Zabzine</p> <p>Preprint number: UUITP-05/24</p> Wed, 31 Jan 2024 08:28:00 GMT 2024-01-31T08:28:00Z Charges and topology in linearised gravity <p>Authors:&nbsp;Chris Hull,&nbsp;&nbsp;Maxwell L. Hutt and&nbsp;&nbsp;Ulf Lindstr&ouml;m</p> <p>Preprint number: UUITP-04/24</p> <p>Abstract: Covariant conserved 2-form currents for linearised gravity are constructed by contracting the linearised curvature with conformal Killing-Yano tensors. The corre- sponding conserved charges were originally introduced by Penrose and have recently been interpreted as the generators of generalised symmetries of the graviton. We introduce an off-shell refinement of these charges and find the relation between these improved Penrose charges and the linearised version of the ADM momentum and angular momentum. If the graviton field is globally well-defined on a background Minkowski space then some of the Penrose charges give the momentum and angular momentum while the remainder vanish. We consider the generalisation in which the graviton has Dirac string singularities or is defined locally in patches, in which case the conventional ADM expressions are not invariant under the graviton gauge symmetry in general. We modify these expressions to render them gauge-invariant and show that the Penrose charges give these modified charges plus certain magnetic gravitational charges. We discuss properties of the Penrose charges, generalise to toroidal Kaluza-Klein compactifications and check our results in a number of examples.&nbsp;</p> Tue, 30 Jan 2024 11:45:00 GMT 2024-01-30T11:45:00Z The soaring kite: a tale of two punctured tori <p>Authors: Mathieu Giroux, Andrzej Pokraka, Franziska Porkert, Yoann Sohnle</p> <p>Preprint number:&nbsp;UUITP-03/24</p> <p>Abstract:&nbsp;We consider the 5-mass kite family of Feynman integrals and present a systematic approach for constructing an &epsilon;-form basis, along with its differential equation pulled back onto the moduli space of two tori. Each torus is associated with one of the two distinct elliptic curves this family depends on. We demonstrate how the relevant punctures, which are required to parametrize the full image of the kinematic space onto this moduli space, can be obtained from integrals over maximal cuts. Given an appropriate boundary value, the differential equation is systematically solved in terms of iterated integrals over Kronecker-Eisenstein g-kernels and modular forms. Then, the numerical evaluation of the master integrals is discussed, and important challenges in that regard are emphasized. In an appendix, we introduce new relations between g-kernels.</p> Tue, 23 Jan 2024 17:08:00 GMT 2024-01-23T17:08:00Z What can abelian gauge theories teach us about kinematic algebras? <p>Authors:&nbsp;Kymani Armstrong-Williams, Silvia Nagy, Chris D. White, Sam Wikeley</p> <p>Preprint number: UUITP&ndash;02/24</p> <p>Abstract: The phenomenon of BCJ duality implies that gauge theories possess an abstract kinematic algebra, mirroring the non-abelian Lie algebra underlying the colour information. Although the nature of the kinematic algebra is known in certain cases, a full understanding is missing for arbitrary non-abelian gauge theories, such that one typically works outwards from well-known examples. In this paper, we pursue an orthogonal approach, and argue that simpler abelian gauge theories can be used as a testing ground for clarifying our understanding of kinematic algebras. We first describe how classes of abelian gauge fields are associated with well-defined subgroups of the diffeomorphism algebra. By considering certain special subgroups, we show that one may construct interacting theories, whose kinematic algebras are inherited from those already appearing in a related abelian theory. Known properties of (anti-)self-dual Yang-Mills theory arise in this way, but so do new generalisations, including self-dual electromagnetism coupled to scalar matter. Furthermore, a recently obtained non-abelian generalisation of the Navier-Stokes equation fits into a similar scheme, as does Chern-Simons theory. Our results provide useful input to further conceptual studies of kinematic algebras.<br /> &nbsp;</p> Fri, 19 Jan 2024 06:43:00 GMT 2024-01-19T06:43:00Z Plücker Coordinates and the Rosenfeld Planes <p>Authors: Jian Qiu</p> <p>Preprint number: UUITP-01/24</p> <p>Abstract:&nbsp;The exceptional compact hermitian symmetric space EIII is the<br /> quotient &#36;E_6/SO(10)\times_{\mathbb{Z}_4}U(1)&#36;.<br /> We introduce the Pl&uuml;cker coordinates which give an embedding of EIII<br /> into &#36;\mathbb{C}P^{26}&#36; as a projective subvariety.<br /> The subvariety is cut out by 27 Pl&uuml;cker relations.<br /> We show that, using Clifford algebra, one can solve this over-<br /> determined system of relations, giving local coordinate charts to the<br /> space. Our motivation is to understand EIII as the complex projective octonion<br /> plane &#36;(\mathbb{C}\otimes\mathbb{O})P^2&#36;, which is a piece of folklore<br /> scattered across literature. We will see that the EIII has an atlas whose transition functions have<br /> clear octonion interpretations, apart from those covering a sub-variety<br /> of dimension 10 denoted &#36;X_{\infty}&#36;. This subvariety is itself a<br /> hermitian symmetric space known as DIII, with no apparent octonion<br /> interpretation. We give detailed analysis of the geometry in the<br /> neighbourhood of &#36;X_{\infty}&#36;. We further decompose &#36;X&#36; into &#36;F_4&#36;-orbits: &#36;X=Y_0\cup Y_{\infty}&#36;, where &#36;Y_0&#36; is an open &#36;F_4&#36; orbit and is the complexified octonion<br /> projective plane and &#36;Y_{\infty}&#36; has co-dimension 1, and is needed to<br /> complete &#36;Y_0&#36; into a projective variety. This decomposition appears in<br /> the classification of equivariant completion of homogeneous algebraic<br /> varieties by Ahiezer \cite{Ahiezer}.</p> Mon, 15 Jan 2024 10:33:00 GMT 2024-01-15T10:33:00Z