arXiv subjects

E. H. Saidi

Publications and source records attributed to E. H. Saidi.

At least 19 recordsLinked to original sources

arXiv2026

Multifield quintessential inflation and Swampland constraints in the IDM

We investigate quintessential inflation in the Inert Doublet Model coupled to a light quintessence field through an exponential interaction. In the Einstein frame, the model forms a noncanonical two-field system with a curved field-space geometry and a Starobinsky-like inflationary plateau. We solve the covariant background and perturbation equations and perform a parameter scan of the exponential slope and the number of inflationary e-folds. The scalar amplitude fixes the inflationary normalization independently at each scan point, rather than selecting a particular value of the quintessence coupling. We find that cumulative entropy-to-curvature transfer significantly modifies the scalar spectrum, while the tensor-to-scalar ratio remains compatible with current CMB limits. The scalar spectral index provides the strongest sensitivity to the exponential coupling. Covariant Swampland diagnostics nevertheless reveal a persistent tension with a strong order-unity de Sitter bound.

hep-ph↗

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.

hep-th↗

arXiv2026

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.

hep-ph↗

arXiv2026

Valley- and Orbital-Controlled 2D Chern Insulators Without Spin-orbit Interaction

We present a theoretical study of orbital-induced topological phase transitions in a two-dimensional lattice model with staggered potential $(Δ)$ and orbital coupling $(λ)$ competing with the hopping strength. By tuning these parameters, two gap-closing mechanisms emerge: valley closure at $\mathbf{K}$ and $\mathbf{K'}$ for $λ=\pmΔ$, and a $\mathbfΓ$-point closure at $λ=\pm\sqrt{Δ^2+9t_0^{2}}$. Their interplay defines a topological window in which the Berry curvature localizes near a single valley, yielding a quantized anomalous Hall conductivity ($σ_{xy}=e^{2}/h$) and Chern number ($C=1$). These results demonstrate orbital-driven Chern insulating behavior without spin-orbit coupling. The resulting phase diagram captures the transition from trivial to topological phases and suggests practical routes for orbital engineering in tunable lattice systems.

cond-mat.other↗

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 $α$ and the cloud of strings parameter $λ$ 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 $α$ and $λ$, 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.

hep-th↗

arXiv2025

Topological Properties of Bilayer $α-T_{3}$ Lattice Induced by Polarized Light

We investigate the topological properties of photon-dressed energy bands in bilayer $α-T_{3}$ lattices under off-resonant circularly polarized light, focusing on aligned and cyclic stacking configurations. Analytical expressions for quasi-energy bands are derived for aligned stacking, while numerical results address cyclic stacking at Dirac points. Circularly polarized light breaks the time-reversal symmetry, lifting the degeneracies at the intersections $t^{a,c}$, leading to the appearance of a Haldane-type Chern insulator in the absence of a magnetic field . At $α= 1/\sqrt{2}$, orbital magnetic moments of corrugated and flat bands exhibit opposite signs, as do their Berry curvatures. For $0 < α< 1$, light-induced band deformations near Dirac points create gaps in the quasi-energy spectrum, where the chemical potential modulates orbital magnetization. Linear magnetization variations align with Chern numbers, yielding quantized anomalous Hall conductivity across stacking types. Notable particle-hole symmetry breaking within $0 < α< 1$ suggests applications in valley caloritronics and quantum sensing. At $α= 1$, flat and corrugated bands remain undistorted; while the flat band contributes no Berry curvature, it produces a finite negative orbital magnetic moment, contrasting with the positive moment of the corrugated band.

cond-mat.mes-hall↗

arXiv2022

Structural, electronic and topological properties of 3D TmBi compound

Using density functional theory based methods we report the structural, electronic and topological properties of the FCC crystal compound TmBi. This material is found to be dynamically stable and shows a non magnetic semimetalic character. By tuning the spin-orbit coupling, we observe a significant change in the band structure, and the occurrence of band inversion along $Γ-X$ direction. The parity product at time-reversal invariant momentum points and the Wannier charge center calculations provide a topological index $Z_{2}=1$ on the $k_{j}=0$ plane (with $j=1,2$ and $3$) revealing the non trivial topological character of TmBi. The existence of topologically protected surface states of TmBi through the observation of a Dirac cones at $\bar{X}$ point confirm our finding. The present work could inspire platforms for exploring novel topological states within the family of rare-earth monobismuthides.

cond-mat.mtrl-sci↗

arXiv2022

Higher order topological matter and fractional chiral states

We develop a chiral anomalous fermion hamiltonian proposal to study the higher order topological (HOT) phase with chiral symmetry $\mathcal{C}$ fractionalized like $\mathcal{C}_{x}\mathcal{C}_{y}\mathcal{C}_{z}$. First, we solve the $\mathcal{C}$-chiral symmetry constraint for eight band models and describe those induced by the partial $\mathcal{C}_{i}$'s. Then, we determine the explicit expression of fractional states characterising HOT matter and comment on the relationships amongst them and with the standard Altland-Zirnbauer gapless modes. We also give characteristic properties of the gapless fractional states and compute their contribution to the topological index of the chiral model. The findings of this work are shown to be crucial for investigating and handling high order topological phase.

cond-mat.mes-hall↗

arXiv2021

Neutrino phenomenology in the flavored NMSSM without domain wall problems

We propose a next-to-minimal supersymmetric Standard Model (NMSSM) extended by an $\mathbb{A}_{4}\times \boldsymbol{Z}_{3}$ flavor symmetry and three right-handed neutrinos providing a detailed study of the neutrino sector and a solution to the domain wall problem. In this proposal, neutrino masses are generated through Type I seesaw mechanism while the mixing angles are described by the trimaximal mixing realized using the NMSSM singlet S and only two flavon fields. The phenomenology of neutrino parameters is studied for normal and inverted mass hierarchies. In particular, we numerically evaluated the observables related to neutrino masses and mixing, namely, $\sum m_{i}$, $m_{ee}$, $m_{ν_{e}}$, and $δ_{CP}$ where we find that the ranges of $m_{ee}$ and $m_{ν_{e}}$ are accessible by current and future experiments while the obtained ranges of $\sum m_{i}$ and $δ_{CP}$ lie within the current experimental data. Another attractive feature we discussed in this paper is the circumvention of the domain wall problem induced by the spontaneous breaking of the $\mathbb{A}_{4}\times \boldsymbol{Z}_{3}$ discrete symmetry. We first showed that the domain walls in the charged lepton sector occur at high energy scale leading to unproblematic domain walls, while in the neutrino sector they are inevitable. Then, to solve this problem, we reconsidered the well-known approach that relies on the explicit breaking of the discrete symmetry through the insertion of Planck-suppressed operators induced by supergravity. \keywords{Neutrino physics, Discrete flavor symmetry,Trimaximal mixing, Domain walls}

hep-ph↗

arXiv2018

Hybrid seesaw neutrino model in SUSY $SU(5)\times \mathbb{A}_{4}$

Motivated by recent results from neutrino experiments, we study the neutrino masses and mixing in the framework of a SUSY $SU(5)\times \mathbb{A}_{4} $ model. The hybrid of Type I and Type II seesaw mechanisms leads to the nonzero value of the reactor angle $θ_{13}\neq 0$ and to the recently disfavored maximal atmospheric angle $θ_{23} \neq45^{\circ}$ by the NOvA experiment. The phenomenological consequences of the model are studied for both normal and inverted mass hierarchies. The obtained ranges for the effective Majorana neutrino mass $m_{ββ}$, the electron neutrino mass $m_{ν_{e}}$, and the $CP$ violating phase $δ_{CP}$ lie within the current experimental allowed ranges where we find that the normal mass hierarchy is favored over the inverted one.

hep-ph↗

arXiv2015

On Building superpotentials in F- GUTs

Using characters of finite group representations, we construct the fusion algebras of operators of the spectrum of F- theory GUTs. These fusion relations are used in building monodromy invariant superpotentials of the low energy effective 4d $\mathcal{N}=1$ supersymmetric GUT models.

hep-th↗

arXiv2014

On Gaugino Dominated Dark Matter

Using the neutral gauginos of SU(2)L* U(1)Y and hybridization ideas below the GUT scale, we approach the Dark Matter particle within the Minimal Supersymmetric Standard Model. In the energy range MGUT-MZ where supergravity effects can be ignored, it is proposed that such DM particle could be interpreted in terms of a mixture of Bino and Wino states with a lower bound mass MDM sup or eq to 65GeV not far above the electroweak scale to account for the observed Dark Matter density. We establish the theoretical origin of this particle and study as well its compositeness and its mass bound.

hep-ph↗

arXiv2012

Weak Coupling Chambers in N=2 BPS Quiver Theory

Using recent results on BPS quiver theory, we develop a group theoretical method to describe the quiver mutations encoding the quantum mechanical duality relating the spectra of distinct quivers. We illustrate the method by computing the BPS spectrum of the infinite weak chamber of some examples of N=2 supersymmetric gauge models without and with quark hypermultiplets.

hep-th↗

arXiv2012

On Mass Gap in Type IIB Quantum Hall Solitons

We discuss the mass gap in quantum Hall solitons (QHS) embedded in superstring theory. In particular, we give two holographic models which are obtained from D-brane configurations in type IIB superstring compactifications. The first one deals with the monolayered system in the D3/D7 brane set up. The second model corresponds to a multilayered system which is described by intersecting D5-branes wrapping a particular set of 3-cycles. In both models, we have shown that the mass gap is related to the filling factor.

hep-th↗

arXiv2011

On Fermion Mass Hirerachies in MSSM-like Quiver Models with Stringy Corrections

Using instanton effects, we discuss the problem of fermion mass hierarchies in an MSSM-like Type IIA orientifolded model with U(3)xSp(1)xU(1)xU(1) gauge symmetry obtained from intersecting D6-branes. In the corresponding four-stack quiver, the different scales of the generated superpotential couplings offer a partial solution to fermion mass hierarchies. Using the known data with neutrino masses m_{v_τ}\lesssim 2 eV, we give the magnitudes of the relevant scales.

hep-th↗

arXiv2011

Embedding Fractional Quantum Hall Solitons in M-theory Compactifications

We engineer U(1)^n Chern-Simons type theories describing fractional quantum Hall solitons (QHS) in 1+2 dimensions from M-theory compactified on eight dimensional hyper-Kähler manifolds as target space of N=4 sigma model. Based on M-theory/Type IIA duality, the systems can be modeled by considering D6-branes wrapping intersecting Hirzebruch surfaces F_0's arranged as ADE Dynkin Diagrams and interacting with higher dimensional R-R gauge fields. In the case of finite Dynkin quivers, we recover well known values of the filling factor observed experimentally including Laughlin, Haldane and Jain series.

hep-th↗

arXiv2010

Brane Realizations of Quantum Hall Solitons and Kac-Moody Lie Algebras

Using quiver gauge theories in (1+2)-dimensions, we give brane realizations of a class of Quantum Hall Solitons (QHS) embedded in Type IIA superstring on the ALE spaces with exotic singularities. These systems are obtained by considering two sets of wrapped D4-branes on 2-spheres. The space-time on which the QHS live is identified with the world-volume of D4-branes wrapped on a collection of intersecting 2-spheres arranged as extended Dynkin diagrams of Kac-Moody Lie algebras. The magnetic source is given by an extra orthogonal D4-brane wrapping a generic 2-cycle in the ALE spaces. It is shown as well that data on the representations of Kac-Moody Lie algebras fix the filling factor of the QHS. In case of finite Dynkin diagrams, we recover results on QHS with integer and fractional filling factors known in the literature. In case of hyperbolic bilayer models, we obtain amongst others filling factors describing holes in the graphene.

hep-th↗

arXiv2008

N=2 Supersymmetric Black Attractors in Six and Seven Dimensions

Using a quaternionic formulation of the moduli space $\boldsymbol{M}({\small IIA/K3}) $ of 10D type IIA superstring on a generic K3 complex surface with volume $\boldsymbol{V}_{0}$, we study extremal $\mathcal{N}=2$ black attractors in 6D space-time and their uplifting to 7D. For the 6D theory, we exhibit the role played by 6D $\mathcal{N}=1$ hypermultiplets and the $Z^{m}$ central charges isotriplet of the 6D $\mathcal{N}=2$ superalgebra. We construct explicitly the special hyperKahler geometry of $% \boldsymbol{M}({\small IIA/K3}) $ and show that the $SO(4) \times SO(20) $ invariant hyperKahler potential is given by $\mathcal{H}=\mathcal{H}_{0}+\mathrm{Tr}[ \ln (1-% \boldsymbol{V}_{0}^{-1}\boldsymbol{S}) ] $ with Kahler leading term $\mathcal{H}_{0}=\mathrm{Tr}[ \ln \boldsymbol{V}_{0}] $ plus an extra term which can be expanded as a power series in $\boldsymbol{V}%_{0}^{-1}$ and the traceless and symmetric 3$\times $3 matrix $\boldsymbol{S} $. We also derive the holomorphic matrix prepotential $\mathcal{G}$ and the flux potential $\mathcal{G}_{BH}$ of the 6D black objects induced by the topology of the RR field strengths $\mathcal{F}_{2}=d\mathcal{A}_{1}$ and $% \mathcal{F}_{4}=d\mathcal{A}_{3}$ on the K3 surface and show that $\mathcal{G% }_{BH}$ reads as $Q_{0}+\sum_{m=1}^{3}q^{m}Z^{m}$. Moreover, we reveal that $% Z^{m}=\sum_{I=1}^{20}Q_{I}(\int_{C_{2}^{I}}J^{m}) $ where the isotriplet $J^{m}$ is the hyperKahler 2- form on the K3 surface. It is found as well that the uplifting to seven dimensions is quite similar to 4D/5D correspondence for back hole potential considered in arXiv 0707.0964 [hep-th].

hep-th↗