arXiv subjects

R. Sammani

Publications and source records attributed to R. Sammani.

14 recordsLinked to original sources

arXiv2026

Optics and Thermodynamics of Charged BTZ Black Holes with Exotic Matter Sources

We study a modified charged BTZ black hole in $(2+1)$--dimensional anti-de Sitter spacetime, where the standard geometry is surrounded by quintessence-like anisotropic matter and a cloud of strings. The corresponding metric function incorporates the effects of the electric charge and the two matter sources. The optical analysis reveals that their combined influence gives rise to a stable circular photon orbit, leading to distinctive modifications of photon dynamics and the associated energy emission. The thermodynamic analysis in a finite cavity further shows that the electric charge and exotic matter sources significantly affect the local thermal stability and phase structure of the black hole. The combined effects of these matter sources give rise to a stable photon sphere and novel thermodynamic behavior absent in the standard charged BTZ solution.

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arXiv2026

Algebraic constructions of code lattices in Narain conformal field theories

We give new results on the structure and representations of the three lattices $\mathbf{\Lambda }_{\mathrm{k}},\mathbf{\Lambda }_{\mathrm{k}\mathcal{C}},\mathbf{\Lambda }_{\mathrm{k}}^{\ast }$ relevant to code CFTs realizing Narain conformal field theories. In this construction, $\mathbf{\Lambda }_{\mathrm{k}}^{\ast }$ denotes the dual of the even lattice $\mathbf{\Lambda }_{\mathrm{k}}$ and $\mathbf{\Lambda }_{\mathrm{k}\mathcal{C}}$ is an even self-dual intermediate lattice with a (d,d) signature. We study the inclusion relations $\mathbf{\Lambda }_{\mathrm{k}}\subset \mathbf{\Lambda } _{\mathrm{k}\mathcal{C}}\subset \mathbf{\Lambda }_{\mathrm{k}}^{\ast }$ characterized by the discriminant group $\mathbf{\Lambda } _{\mathrm{k}}^{\ast }/\mathbf{\Lambda }_{\mathrm{k}}$ isomorphic to $\mathbb{Z}_{\mathrm{k}}$ and provide explicit constructions of these $\mathbb{R}^{(\mathrm{r}d,\mathrm{r}d)}$ lattices first for rank $\mathrm{r}=d=1$ and then for higher dimensional Lie algebras with $\mathrm{r}=d>1$. Additional structural features and generalisations are also discussed.

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arXiv2026

A Swampland-modified Hod bound for charged black holes with exotic matter

In this paper, we study the quasinormal modes (QNMs) of a charged black hole in the presence of both quintessence and a cloud of strings using the Pade-averaged higher-order WKB approximation method. We investigate the effect of the quintessence parameter $\alpha$ and the cloud of strings parameter $\lambda$ on the stability as well as the oscillation frequency of perturbations. The validity of Hod's conjecture, which relates quasinormal frequencies to the black hole temperature, is tested throughout the physically allowed parameter space. Our results show that both the effective potential and the decay rate of perturbations depend on the values of $\alpha$ and $\lambda$, leading to either enhancement or suppression of the conditions required to satisfy Hod's bound. Furthermore, we discuss how these parameters modify the black hole shadow and the corresponding energy emission rate, revealing correlations with observable signatures. Finally, we establish a connection with the Swampland Distance Conjecture by expressing the Hawking temperature in terms of the scalar field excursion. Our analysis leads to a modified Hod bound and identifies a region of parameter space in which both the modified Hod bound and the Swampland constraints are simultaneously satisfied, ensuring consistency between black hole thermodynamics, observational properties, and quantum gravity constraints.

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arXiv2025

Compactified 2HDM under the Non-SUSY AdS instability conjecture

We investigate how extra-dimensional dynamics influence Higgs-sector phenomenology by compactifying a Two-Higgs-Doublet Model (2HDM) coupled to 4D gravity on a circle $S^1$. The resulting effective potential includes tree-level 2HDM interactions, one-loop Coleman--Weinberg corrections from the Kaluza--Klein towers, and an effective radion stabilization contribution inspired by the broader modulus-stabilization literature. We derive the corresponding 3D effective action and show that, for the observed Higgs mass $m_h=125\,\mathrm{GeV}$, the compactified potential admits a stabilized configuration with near-zero vacuum energy. By imposing the non-supersymmetric AdS instability conjecture as a quantum-gravity consistency requirement, we obtain a constraint within our numerical setup on the heavy Higgs sector, finding that the additional scalar states must satisfy approximately $M_H \gtrsim 680\,\mathrm{GeV}$ in order to avoid perturbatively stable non-supersymmetric AdS$_3$ minima. Our results demonstrate how Swampland-inspired constraints can yield phenomenologically relevant predictions for extended Higgs sectors.

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arXiv2025

Swampland bound on quintessential inflation in IDM

We study a quintessential inflation scenario based on the Inert Doublet Model (IDM) coupled to a quintessence field via an exponential potential $V_0e^{-\beta\phi/M_p}$. Using a conformal transformation from the Jordan frame to the Einstein frame, we derive an effective Starobinsky-type potential modulated by an exponential factor that naturally unifies the inflationary epoch with the late-time accelerated expansion of the Universe. We analyze the resulting two-field dynamics, compute the slow-roll parameters, the primordial perturbation spectrum, as well as the inflationary observables $n_s$ and $r$, and then confront the predictions with the latest $Planck$ and $BICEP/Keck$ data. We find amongst others that the quintessence inflaton coupling must remain extremely weak, in the order of $\beta \lesssim 4\times10^{-3}$, to satisfy current $CMB$ data, whereas swampland dS conjecture favors a step potential with $\beta\sim\mathcal{O}(1)$, signaling a significant tension between quantum gravity consistency and cosmological viability. We conclude by discussing possible extensions and stabilization mechanisms that could help reconcile the inflationary predictions with swampland constraints.

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arXiv2025

Landscape of Narain CFTs

In this work, we investigate the AdS$_{3}$ gravitational bulk dual to an ensemble of Narain CFTs and their generalisations to establish bounds consistent with the Swampland program. Focusing on the AdS distance and finiteness conjectures, we show that the central charge of Narain CFTs forming the ensemble must be finite. Combining anomaly and unitary requirements, we derive an upper bound on the rank of the abelian U(1) gauge symmetries that can consistently couple to the AdS$_{3}$ gravity. We give explicit realisations of these constraints by determining the range of the Chern-Simons level $k^{G}$ corresponding to a bounded AdS$_{3}$ radius$.$ Accordingly, the Narain landscape is finite with a number of admissible CFTs constrained as $3/2\lesssim c\lesssim 10^{3}.$

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arXiv2025

Code CFTs and Topological Matter

In this paper, we propose a novel framework for modeling topological phases of matter using code-based Narain conformal field theories (NCFTs). We show that the algebraic structure of the NCFTs naturally embeds into critical lattice quantum field theory, yielding emergent topological features characteristic of gapless fermionic systems with non-zero Chern numbers. We develop a new representation of construction A of code CFT in terms of root and weight lattices of Lie algebras, focusing in particular on SU(2) and SU(3). We then derive the spectrum of particle states occupying the lattice and, with the help of fermionisation techniques, demonstrate that it hosts fermionic excitations with Dirac cones akin to tight binding systems namely the Haldane model of quantum anomalous hall effect on a honeycomb geometry.

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arXiv2025

Black hole solutions of three dimensional E$_{6}$-gravity

This paper aims to construct exceptional Banados-Teitelboim-Zanelli (BTZ) black holes carrying E$_{6}$ charges as solutions to the 3D higher spin Anti-de Sitter (AdS) gravity with E$_{6}$ boundary conditions. Guided by Tits-Satake graphs of real forms of the e$_{6} $ Lie algebra, we build three remarkable E$_{6}$-higher spin black hole models: the linear-exceptional and the ortho-exceptional BTZ solutions result from splitting the extremal nodes in the E$_{6\left( 6\right)}$ Tits-Satake diagram while the pure exceptional-exceptional model follows from the folding down to F$_{4\left( 4\right) }$. And with the help of Hasse diagram visualizations, we study the ensuing higher spin spectrums to develop the corresponding metrics using two types of gauge transformations. For completeness, we examine the thermodynamics of the standard BTZ coupled to E$_{6}$ higher spin gravity fields by computing the partition function exploiting a one to one correspondence between the factors of the vacuum characters and the roots of the E$_{6}$ root system.

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arXiv2025

Fluctuating Ensemble Averages and the BTZ Threshold

Recent work shows fascinating links between ensemble averaging and the Swampland program. In order to break the emerging global symmetries of the ensemble averaging as dictated by the no global symmetries conjecture, one may consider fluctuations away from the average given by deviations in the Siegel-Weil formula. In this work, we investigate the physical interpretation of these fluctuations in the bulk physics and pinpoint the states giving rise to them. For this purpose, we explore an ensemble of generalised Narain CFTs and build the AdS$_{3}$ gravitational dual in the Chern-Simons (CS) framework. We study the associated charged BTZ black hole solution and assess its stability. Using the Swampland weak gravity conjecture, we show that the fluctuations of the ensemble average are below the BTZ threshold and correspond to a sublattice of superextremal states emitted by the black hole. We exploit the logarithmic density of states to derive bounds on the charged vectors of the abelian CS symmetry and introduce a novel formulation of the density function to ensure consistency with the sublattice WGC. We establish bounds that allows to distinguish heavy states contributing to the average from light states generating fluctuations around it.

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arXiv2024

Topological 4D gravity and gravitational defects

Using the Chern-Simons formulation of AdS3 gravity as well as the Costello-Witten-Yamazaki (CWY) theory for quantum integrability, we construct a novel topological 4D gravity given by Eq(5.1) with observables based on gravitational gauge field holonomies. The field action $S^{grav}_{4D}$ of this gravity has a gauge symmetry $SL(2,\mathbb{C})$ and reads also as the difference $S^{CWY_{L}}_{4D}-S^{CWY_{R}}_{4D}$ with 4D Chern-Simons field actions $S^{CWY_{L/R}}_{4D}$ given by left/right CWY theory Eq(3.9). We also use this 4D gravity derivation to build observables describing gravitational topological defects and their interactions. We conclude our study with few comments regarding quantum integrability and the extension of AdS$_{3}$/CFT$_{2}$ correspondence with regard to the obtained topological 4D gravity.

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arXiv2024

Higher spin swampland conjecture for massive AdS$_{3}$ gravity

In this paper, we show that a possible version of the swampland weak gravity conjecture for higher spin (HS) massive topological AdS$_{3}$ gravity can be expressed in terms of mass $M_{hs}$, charge $Q_{hs}$ and coupling constant $g_{hs}$ of 3D gravity coupled to higher spin fields as $M_{hs} \leq \sqrt{2}$ $Q_{hs}$ $g_{hs}$ $M_{Pl}$. The higher spin charge is given by the $SO(1,2)$ quadratic Casimir $Q_{hs}^{2}=s\left (s-1\right) $ and the HS coupling constant by ${\large g}_{hs} ^{2}=2/\left (M_{Pl}^{2} l_{AdS_{3}}^{2}\right )$ while the mass expressed like $\left( l_{AdS_{3}} \text{M}_{hs}\right) ^{2}$ is defined as $ \left (1+\mu l_{AdS_{3}} \right ) ^{2} s \left ( s-1 \right ) +[1- \left ( \mu l_{AdS_{3}} \right ) ^{2} \left ( s-1 \right ) ]$.

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arXiv2024

Black Flowers and Real Forms of Higher Spin Symmetries

Using Chern-Simons formulation, we investigate higher spin (HS) black holes in AdS$_{3}$ with soft Heisenberg hair and establish linkage with the real forms of the underlying complexified gauge symmetries taken here as $SL(N,C)_{L}\times SL(N,C)_{R}.$ We study the various conserved currents characterizing the HS black flowers (HS-BF) and show that they can be formed of layers indexed by the elements of the centre of the gauge symmetry. This feature follows from requiring the holonomy of the asymptotic gauge connection around the thermal cycle to sit in the centre $\mathbb{Z}_{N}$ of the symmetry group. With regard to the compact subgroups of the real forms of the complexified gauge symmetry, we calculate the entropies of the HS-BF and verify that, unless we are considering trivial holonomies, there are no continuous paths joining the HS-BF to the core spin 2 black holes. As explicit illustrations, we give quantum field realisations of the soft Heisenberg hair in terms of bosonic and fermionic primary conformal fields and compute the HS-BF entropy as a function of the number of fermions occupying the ground state of the Heisenberg soft hair.

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arXiv2024

Asymptotic Weak Gravity Conjecture in M-theory on K3 $\times$ K3

The Asymptotic WGC has been proposed as a special case of the tower WGC that probes infinite distances in the moduli space corresponding to weakly coupled gauge regimes. The conjecture has been studied in M-theory on Calabi-Yau threefold (CY3) with finite volume inducing a 5D effective QFT. In this paper, we extend the scope of the previous study to encompass lower dimensions, particularly we generalise the obtained 5D asymptotic WGC to the effective field theory $EFT_{3D}$ coupled to 3D gravity that descends from M-theory compactified on Calabi-Yau fourfold with an emphasis on K3 x K3. We find that the CY4 has three fibration structures labelled as line Type-$T^2$, surface Type-$S$ and bulk Type-$V$. The emergent $EFT_{3D}$ is shown to have 2+2 towers of states occupied by light and heavy BPS as well as non BPS particles. To ensure the viability of the 3D Asymptotic WGC, we give explicit calculations to thoroughly test the swampland constraint for both the weakly and strongly gauge coupled regimes. Additional aspects, including the gauge symmetry breaking and duality symmetry are also investigated.

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arXiv2023

Finiteness of 3D higher spin gravity Landscape

We give Swampland constraints on the three dimensional Landscape of Anti-de Sitter higher spin gravity in the Chern-Simons formulation with connection valued in various split real forms of Lie algebras. We derive the finiteness conjecture by computing the upper bound on the rank of possible gauge groups then we refine it using the AdS distance conjecture. We discuss the implications of this Swampland constraint on the spectrum of higher spin gravity theories and we compare it with the gravitational exclusion principle required from BTZ black hole consideration to excerpt a constraint on the Chern-Simons level k.

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