Compactifications Of Type IIB String Theory Research Articles

Metastable vacua from torsion and machine learning

By implementing an error function on a Machine Learning algorithm we look for minimal conditions to construct stable Anti de Sitter and de Sitter vacua from dimensional type IIB String theory compactification on Kähler manifolds with torsion. This allows to have contributions to the scalar potential from the five-form flux and from D-branes wrapping torsional cycles, interpreted as non-BPS states. The former implies the possibility to construct stable AdS vacua while the latter constitutes a mechanism to uplift AdS to dS vacua. Particularly we consider {widehat{D5}} non-BPS states to uplift the stable AdS vacua to an (apparently) stable dS minimum. Both results – the generation of an AdS vacuum and the corresponding uplifting to a dS one – are restricted to a certain type of configurations, specifically with the number of O3 orientifolds bounded from below by the number of D3-branes and fluxes. Under these conditions, we report over 170 dS (classical) stable vacua. In all of them, the uplifted effective potential becomes very flat indicating the presence of possible sources of instabilities. We comment on their relationship with the Swampland Conjectures.

Universal class of type-IIB flux vacua with analytic mass spectrum

We report on a new class of flux vacua generically present in Calabi-Yau compactifications of type-IIB string theory. At these vacua, the mass spectrum of the complete axio-dilaton/complex structure sector is given, to leading order in $\alpha'$ and $g_s$, by a simple analytic formula independent of the choice of Calabi-Yau. We provide a method to find these vacua, and construct an ensemble of $17,054$ solutions for the Calabi-Yau hypersurface $\mathbb{WP}_{[1,1,1,6,9]}^4$, where the masses of the axio-dilaton and the $272$ complex structure fields can be explicitly computed.

Type II string theory on Calabi-Yau manifolds with torsion and non-Abelian discrete gauge symmetries

We provide the first explicit example of Type IIB string theory compactification on a globally defined Calabi-Yau threefold with torsion which results in a four-dimensional effective theory with a non-Abelian discrete gauge symmetry. Our example is based on a particular Calabi-Yau manifold, the quotient of a product of three elliptic curves by a fixed point free action of {mathbb{Z}}_2times {mathbb{Z}}_2 . Its cohomology contains torsion classes in various degrees. The main technical novelty is in determining the multiplicative structure of the (torsion part of) the cohomology ring, and in particular showing that the cup product of second cohomology torsion elements goes non-trivially to the fourth cohomology. This specifies a non-Abelian, Heisenberg-type discrete symmetry group of the cfour-dimensional theory.

Aspects of Moduli Stabilization in Type IIB String Theory

We review moduli stabilization in type IIB string theory compactification with fluxes. We focus on KKLT and Large Volume Scenario (LVS). We show that the predicted soft SUSY breaking terms in KKLT model are not phenomenological viable. In LVS, the following result for scalar mass, gaugino mass, and trilinear term is obtained:m0=m1/2=-A0=m3/2, which may account for Higgs mass limit ifm3/2~O(1.5) TeV. However, in this case, the relic abundance of the lightest neutralino cannot be consistent with the measured limits. We also study the cosmological consequences of moduli stabilization in both models. In particular, the associated inflation models such as racetrack inflation and Kähler inflation are analyzed. Finally, the problem of moduli destabilization and the effect of string moduli backreaction on the inflation models are discussed.

Supersymmetry, Supergravity, and Superstring Phenomenology

Supersymmetry, supergravity, and superstring are amongst the most popular research topics in particle physics. Supersymmetry is a generalization of the space-time symmetries of quantum field theory that links the matter particles with the force-carrying particles and implies that there are additional superparticles necessary to complete the symmetry. Supergravity is the theory that combines the principles of supersymmetry and general relativity. It naturally includes gravity along with the other fundamental forces (the electromagnetic force, the weak nuclear force, in turn already unified in the electroweak interactions, and the strong nuclear force). String theory is the leading candidate for a theory that unifies all fundamental forces in nature in a consistent scheme. It also provides a consistent framework for the theory of quantum gravity. Compactified string/M-theories make testable predictions about our four-dimensional world. The phenomenology of supersymmetry, supergravity, and superstring is thus very rich and covers many topics: flavour physics and CP violation, Higgs and collider physics, model building beyond the Standard Model, and astroparticle physics and cosmology. Some recent developments in these theories, each with important applications to particle physics and/or cosmology, are the main theme of this special issue. One of the papers of this special issue discusses the constrained generalized Killing spinors, which characterize supersymmetric flux compactifications of supergravity theories, using geometric algebra techniques. Another paper presents a study on what are called Adinkras, which are combinatorial objects developed to study (1-dimensional) supersymmetry representations. Another paper reviews moduli stabilization in type IIB string theory compactification with fluxes. Another paper in this special issue describes supermultiplets wherein a continuously variable “tuning parameter” modifies the supersymmetry transformations. Another paper studies the constraints imposed on the Minimal Supersymmetric Standard Model (MSSM) parameter space by the Large Hadron Collider (LHC) Higgs mass measurements and gluino mass lower bound. Another paper studies helical phase inflation which realizes “monodromy inflation” in supergravity theory. Another paper considers scalar Wilson operators of Supersymmetric Yang-Mills (SYM) theories at high spin and generic twist operators in the multicolor limit. Another paper author gives an overview about the features that the Mathematica package SARAH provides to study new supersymmetric models. Another paper reviews a possible mechanism for the spontaneous breaking of supersymmetry, based on the presence of vacuum condensates. Another paper constructs and studies a formulation of a chargeless complex vector matter field in a supersymmetric framework.

Multiple dark matter scenarios from ubiquitous stringy throats

We discuss the possibility of having multiple Kaluza-Klein dark matter candidates which arise naturally in generic type-IIB string theory compactification scenarios. These dark matter candidates reside in various throats of the Calabi-Yau manifold. In principle, they can come with a varied range of masses in four dimensions depending upon the hierarchical warping of the throats. We show that consistency with cosmological bounds and four-dimensional effective theory description imposes strong constraints on the parameter space and the geometry of the throats. With a rather model-independent approach, we find that the mass scales allowed for the Kaluza-Klein dark matter particles in various throats can vary between 0.1 eV and 10 TeV, depending upon the throat geometry. Thus, there could be simultaneously more than one kind of cold (and possibly warm and hot) dark matter components residing in the Universe. This multiple dark matter scenario could weaken the bound on a conventional supersymmetric dark matter candidate and could also account for extra relativistic degrees of freedom in our Universe.

On flux compactification and moduli stabilization

We study the effect of adding charged matter fields to both D3 and D7 branes in type IIB string theory compactification with fluxes. Generically, charged matter fields induce additional terms to the Kähler form, the superpotential and the D-terms. These terms allow for minima with positive or zero cosmological constants, even in the absence of non-perturbative effects. We show this result first by decoupling the dilaton field along the lines of the KKLT, and second by reincorporating it in the action with the Kähler moduli.

Hierarchies from fluxes in string compactifications

Warped compactifications with significant warping provide one of the few known mechanisms for naturally generating large hierarchies of physical scales. We demonstrate that this mechanism is realizable in string theory, and give examples involving orientifold compactifications of type-IIB string theory and F-theory compactifications on Calabi-Yau fourfolds. In each case, the hierarchy of scales is fixed by a choice of Ramond-Ramond and Neveu-Schwarz fluxes in the compact manifold. Our solutions involve compactifications of the Klebanov-Strassler gravity dual to a confining $\mathcal{N}=1$ supersymmetric gauge theory, and the hierarchy reflects the small scale of chiral symmetry breaking in the dual gauge theory.

Wilson-Polyakov loop at finite temperature in large- N gauge theory and anti-de Sitter supergravity

Aspects of d = 4, N = 4 superconformal U( N) gauge theory are studied a t finite temperature. Utilizing dual description of large- N and strong coupling limit via Type IIB string theory compactification on Schwarzschild-anti-de Sitter space-time, we study correlations of Wilson-Polyakov loops and heavy quark potential thereof. We find that the heavy quark potential is Coulomb-like and has a finite range, as expected for gauge theory in high temperature, deconfinement phase. The potential exhibits finite temperature scaling consistent with underlying conformal invariance. We also study isolated heavy quark on a probe D3-brane world-volume and find supporting evidence that near extremal D3-branes are located at the Schwarzschild horizon.