Swampland Conjecture Research Articles

Swampland criteria of inflationary scalar field models with well-known potentials

We explore the swampland conjectures of quintessence and tachyon scalar field models in [Formula: see text] and Einstein gravities, respectively. In [Formula: see text] gravity, we consider cold and warm (by assuming generalized dissipative coefficient) inflationary scenarios and develop constraints on de-Sitter conjectures through Bekenstein entropy relation. In usual inflation, the de-Sitter conjecture constraint becomes constant (in terms of models constant parameters) which can be easily analyzed for its validity (i.e., [Formula: see text]). However, in warm inflation, we analyze the de-Sitter conjecture constraint through [Formula: see text], i.e., if [Formula: see text] then [Formula: see text] and hence we can obtain the required result. For evaluating this condition, we choose three well-known potentials such as monomial chaotic, hilltop and generalized exponential. It is observed that the condition [Formula: see text] satisfied for all three potentials in both regimes of dissipative coefficient for specific choice of constants. We also obtain satisfactory results of de-Sitter conjecture for tachyon and polytropic (with quintessence scalar field) in general relativity. We investigate the consistency of assumed potentials through inflationary parameters [Formula: see text] and [Formula: see text] comparing with Planck’s observational data 2018 and found them compatible with the recent observations.

Confinement in de Sitter space and the swampland

The relation between confinement scale Λc of a gauge theory and the Hubble scale H of the background quasi de Sitter space, required to satisfy the Festina Lente criteria (Λc ≳ H) from swampland principles, are investigated for a holographic theory using the Karch-Randall setup. A purely gravitational description admits an unstable de Sitter extremum, and the requirement of Festina Lente translates into requirements of a perturbative gravitational dual, but prohibits an arbitrarily small hierarchy for other parameters fixed. With an additional scalar sector, the theory admits metastable de Sitter minima, and the requirement of Festina Lente imposes constraints on the parameters. For some range of parameters where Festina Lente could be constraining, the de Sitter minimum is very close to decay, thus invalidating the applicability. Further consequences of the finite lifetime of the dS extrema and the relation with related swampland conjectures are investigated, and no contradictions are found. These results make case for the consistency and utility of the Karch-Randall setup, clarify the implications of Festina Lente for holographic theories, and connect Festina Lente to other swampland conjectures.

Fluxes, vacua, and tadpoles meet Landau-Ginzburg and Fermat

Type IIB flux vacua based on Landau-Ginzburg models without Kähler deformations provide fully-controlled insights into the non-geometric and strongly-coupled string landscape. We show here that supersymmetric flux configurations at the Fermat point of the 19 model, which were found long-time ago to saturate the orientifold tadpole, leave a number of massless fields, which however are not all flat directions of the superpotential at higher order. More generally, the rank of the Hessian of the superpotential is compatible with a suitably formulated tadpole conjecture for all fluxes that we found. Moreover, we describe new infinite families of supersymmetric 4d mathcal{N} = 1 Minkowski and AdS vacua and confront them with several other swampland conjectures.

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.

Composite inflation and further refining dS swampland conjecture

A natural combination of the first and second derivatives of the scalar potential was achieved in a framework of an alternative refined de Sitter conjecture recently proposed in the literature. In this work, we study various inflation models in which the inflaton is a composite field emerging from various strongly interacting field theories. We then examine if these four models of inflation can satisfy this further refining de Sitter swampland conjecture or not. Regarding our analysis with proper choices of parameters a,b=1−a and q, we find that some inflationary models are in strong tension with the refined Swampland conjecture. However, all of them can always satisfy the alternative refined de Sitter conjecture. Therefore, one may expect that all inflationary models might all be in “landscape” since the “further refining de Sitter swampland conjecture” is satisfied.

Automated consistent truncations and stability of flux compactifications

Classical flux compactifications contribute to a well-controlled corner of the string landscape, therefore providing an important testing ground for a variety of conjectures. We focus here on type II supergravity compactifications on 6d group manifolds towards 4d maximally symmetric spacetimes. We develop a code where the truncation to left-invariant scalars and the dimensional reduction to a 4d theory are automated, for any possible configuration of Op-planes and Dp-branes. We then prove that any such truncation is consistent. We further compute the mass spectrum and analyse the stability of many de Sitter, Minkowski or anti-de Sitter solutions, as well as their consistency with swampland conjectures.

Information paradox and island in quasi-de Sitter space

Whereas a static observer in de Sitter (dS) space detects thermal radiation emitted by the horizon, the dS isometries impose that the radiation is in equilibrium with the background. This implies that for the static observer to find the information paradox, the background must be deformed to quasi-dS space in which the dS isometries are spontaneously broken. We study the condition that the information paradox arises in quasi-dS space with the monotonically increasing horizon size which is used to describe the inflationary cosmology. For this purpose, the dimensional reduction of three-dimensional dS space with thermal radiation modelled by the JT gravity coupled to CFT is considered. We argue that when the central charge monotonically increases in time, the information paradox arises but the conditions for the existence of the island become more restrictive. As the central charge can be interpreted as the number of degrees of freedom, the absence of the island in quasi-dS space supports the entropy argument for the dS swampland conjecture.

Scalar Weak Gravity Conjecture in Super Yang-Mills Inflationary Model

In this article, we want to check four inflation models, namely, composite NJL inflation (NJLI), Glueball inflation (GI), super Yang–Mills inflation (SYMI), and Orientifold inflation (OI), with two conjectures of the swampland program: scalar weak gravity conjecture (SWGC) and strong scalar weak gravity conjecture (SSWGC) since all these models violate the dS swampland conjecture (DSC) but are compatible with further refining de Sitter swampland conjecture (FRDSSC) through manual adjustment of free parameters of the mentioned conjecture. We want to study the simultaneous compatibility of each model with these two new conjectures. Despite being consistent with (FRDSSC), we find that all models are not compatible with the other conjectures of the Swampland program in all regions, and these conjectures are only satisfied in a specific area. Moreover, due to the presence of constant parameter (ϕ0) in the higher orders derivatives, the (SYMI) and (OI) among all the models are more compatible with all conjectures of the swampland program. These models can provide a more significant amount of satisfaction with all of them. They can be suitable and accurate inflation models for a more profound examination of universe developments. We determined a particular region for these models is compatible with (FRDSSC), (SWGC), and (SSWGC) simultaneously.

Cosmic Evolution of the Logarithmic f(R) Model and the dS Swampland Conjecture

In this paper, we study the inflationary scenario in logarithmic f(R) gravity, where the rate of inflation roll is constant. On the other hand, our gravitational f(R) model is a polynomial plus a logarithmic term. We take advantage of constant-roll conditions and investigate the cosmic evolution of the logarithmic f(R) gravity. We present a numerical and a graphical study using the model parameters. Additionally, we obtain the corresponding potential by using the constant-roll condition. We obtain the exact value of the potential satisfying the constant-roll conditions. Next, we challenge it with refined swampland conjecture with respect to the Planck data. Finally, we compare our results with the latest observable data.

Higgs inflation and scalar weak gravity conjecture

In this article, we intend to find a specific model which can satisfy the further refining dS swampland conjecture and scalar weak gravity conjecture (SWGC) simultaneously, in particular, Higgs inflation model and its two extensions: Higgs-dilaton model and Palatini Higgs inflation. We determine the conditions if the three inflation models satisfy scalar weak gravity conjecture (SWGC) and strong scalar weak gravity conjecture (SSWGC).

Stringy multifield quintessence and the Swampland

We consider quintessence models within 4D effective descriptions of gravity coupled to two scalar fields. These theories are known to give rise to viable models of late-time cosmic acceleration without any need for flat potentials, and so they are potentially in agreement with the dS Swampland conjecture. In this paper we investigate the possibility of consistently embedding such constructions in string theory. We identify situations where the quintessence fields are either closed string universal moduli or non-universal moduli such as blow-up modes. We generically show that no trajectories compatible with today’s cosmological parameters exist, if one starts from matter-dominated initial conditions. It is worth remarking that universal trajectories compatible with observations do appear, provided that the starting point at early times is a phase of kinetic domination. However, justifying this choice of initial conditions on solid grounds is far from easy. We conclude by studying Q-ball formation in this class of models and discuss constraints coming from Q-ball safety in all cases analyzed here.

Swampland conjectures and single-field inflation in nonstandard cosmological scenarios

Swampland conjectures have attracted quite some interest in the cosmological community. They have been shown to have wide ranging implications, like constraints on inflationary models, primordial black holes, dark energy to name a few. Particularly, their implications on single-field inflationary models in general relativity-based cosmology have gathered huge attention. Swampland conjectures in their usual form have been shown to be incompatible with these kinds of single-field models, or have been shown to induce severe fine tuning in these inflationary models for them to be consistent with the conjectures. In this work, we show that a large class of single-field inflationary models can in fact bypass the problems faced by inflationary paradigms in GR-Based cosmology. We use the exact solution approach to inflation for the same purpose and show how string theoretic motivations of the swampland conjectures can be in perfect symphony with various single-field inflationary models in nonstandard cosmological scenarios.

K-Essence Inflation Evading Swampland Conjectures and Inflationary Parameters

In this paper, we study the inflationary scenario in the realm of k-essence model and swampland conjectures. Taking into account three models of Chaplygin gas, such as generalized, modified, and generalized cosmic Chaplygin gas models, we discuss the equation of state (EoS) parameter ω, slow roll parameters (ϵ(ϕ),η(ϕ)), curvature perturbation (Ps), tensor to scalar ratio (r), and scalar spectral index (ns). As regards the k-essence model, the coupling function as a function of scalar field L(ϕ) is used. We investigate the swampland conjecture and then find the value of ζ(ϕ), i.e., bound of second conjecture for these three models by unifying swampland conjecture and k-essence. We plot the EoS parameter ω, inflationary parameters plane r−ns and bound of swampland conjecture ζ(ϕ)−ϕ, which determine that the values of ω<−1 for each model, r, are r<0.0094,r≤0.0065,r≤0.0067, and ranges for ns are [0.934,0.999],[0.9,0.999],[0.9,0.992] for generalized, modified, and generalized cosmic Chaplygin gas models, respectively, and compare their compatibility with the Planck data from 2018. Furthermore, we determine the bound for swampland conjecture as ζ(ϕ)≤0.992,ζ(ϕ)≤0.964,ζ(ϕ)≤0.964 for generalized, modified and generalized cosmic Chaplygin gas models, respectively.

Notes on further refining de Sitter swampland conjecture with inflationary models

In this paper, we challenge some inflationary models with the recent new conjecture of the swampland program, namely, further refining the de Sitter swampland conjecture. So far, different inflation models have been studied with refined dS swampland conjecture in various conditions. Some of these models were in line with this conjecture, and some were in direct tension with it. Therefore, a modified model that combines the first and second conditions of refined dS conjecture was proposed. It has a limitation on its constant parameters such as a , b = 1 − a and q . We challenge several inflation models with the new conjecture, which contradicts the refined dS conjecture. We discuss the constraints and adjustments of each of a , b = 1 − a , and q and the compatibility or incompatibility of the inflation models with further refining the de Sitter swampland conjecture. We will compare the results with the models studied by refined dS conjecture. We conclude that many inflation models are fully compatible with the mentioned conjecture. If the new conjecture is accurate, these inflationary models live in the landscape instead of the swampland. • Further refining de sitter swampland conjecture. • Minimal gauge inflation model. • Minimal plateau inflationary model. • Gauged Nambu–Jona–Lasinio inflation. • limitations applied to its free constant parameters.

Swampland conjectures in hybrid metric-Palatini gravity

In this paper, we study a hybrid combination of Einstein-Hilbert action with curvature scalar $R$, and a function $f(\mathcal{R})$ in Palatini gravity within the context of inflationary scenario, from the Swampland conjecture point of view. This hybrid model has been paid attention in recent cosmological studies, and its applications have been widely studied in the literature. In this regard, using the Swampland conjecture (using ($ C_ {1} $) as the first component of dS swampland conjecture, which is obtained from the first derivative of the potential upon the potential and ($ C_ {2} $) as the second component which is acquired from the second derivative of the potential upon the potential), we investigate the cosmological implications of the present gravity theory, with a suitable potential, in the framework of inflationary scenario to obtain cosmological quantities such as slow-roll parameter, scalar spectral index $(n_{s})$, tensor-to-scalar ratio ($r_{s}$), and then compare them with the cosmological observations. Moreover, we compare the compatibility or incompatibility of the model with observable data, such as Planck, by applying Swampland conjecture to $r_{s}-n_{s}$ , $C_{1,2}-n_{s}$ and $C_{1,2}-r_{s}$ plots.

Multi-field cold and warm inflation and the de Sitter swampland conjectures

We discuss under which conditions multi-field cold and warminflationary models with canonical kinetic energy terms are compatiblewith the swampland conjectures about the emergence of de Sitter solutionsin string theory. We find that under quite general conditions the slow-rollconditions for multi-field cold inflation are at odds with the swamplandconjectures for an arbitrary number of scalar fields driving inflation.However, slow-roll conditions can be reconciled with the swampland conjecturesin the strong dissipative regime of warm inflation.

IR/UV mixing, towers of species and swampland conjectures

By applying the Covariant Entropy Bound (CEB) to an EFT in a box of size 1/ΛIR one obtains that the UV and IR cut-offs of the EFT are necessarily correlated. We argue that in a theory of Quantum Gravity (QG) one should identify the UV cutoff with the ‘species scale’, and give a general algorithm to calculate it in the case of multiple towers becoming light. One then obtains an upper bound on the characteristic mass scale of the tower in terms of the IR cut-off, given by Mtower ≲ {left({Lambda}_{mathrm{IR}}right)}^{2{alpha}_D} in Planck units, with αD = (D − 2 + p)/2p(D − 1), where p depends on the density of states. Identifying the IR cut-off with a (non-vanishing) curvature in AdS one reproduces the statement of the AdS Distance Conjecture (ADC), also giving an explicit lower bound for the α exponent. In particular, we find that the CEB implies α ≥ 1/2 in any dimension if there is a single KK tower, both in AdS and dS vacua. However values α < 1/2 are allowed if the particle tower is multiple or has a string component. We also consider the CKN constraint coming from avoiding gravitational collapse which further requires in general α ≥ 1/D for the lightest tower. We analyse the case of the DGKT-CFI class of Type IIA orientifold models and show it has both particle and string towers below the species scale, so that a careful analysis of how the ADC is defined is needed. We find that this class of models obey but do not saturate the CEB. The UV/IR constraints found apply to both AdS and dS vacua. We comment on possible applications of these ideas to the dS Swampland conjecture as well as to the observed dS phase of the universe.

Cosmic birefringence from monodromic axion dark energy

The recently reported non-zero isotropic birefringence angle in Planck 2018 polarization data provides a tantalizing hint for new physics of axions. In this paper, we explain this by a string theory motivated axion with a monodromy potential that plays the role of dark energy. Upon using the birefringence measurement and the constraint on the equation of state for dark energy in this scenario, we find an upper bound on the axion decay constant as fa ≲ 1016 GeV. This naturally gives an energy scale of order GUT and can resolve the theoretical issue of super-Planckian field range of the conventional axion dark energy model. We further study the implications of cosmic birefringence for the underlying theory and its consequences for the string swampland conjectures. We finally discuss oscillatory features in the dark energy sector and the expected cosmic birefringence tomography.

Cosmological dynamics of multifield dark energy

We numerically and analytically explore the background cosmological dynamics of multifield dark energy with highly nongeodesic or "spinning" field-space trajectories. These extensions of standard single-field quintessence possess appealing theoretical features and observable differences from the cosmological standard model. At the level of the cosmological background, we perform a phase-space analysis and identify approximate attractors with late-time acceleration for a wide range of initial conditions. Focusing on two classes of field-space geometry, we derive bounds on parameter space by demanding viable late-time acceleration and the absence of gradient instabilities, as well as from the de Sitter swampland conjecture.

Refined swampland conjecture in deformed Starobinsky gravity

In order to validate or invalidate a large class of low energy effective theories, the swampland conjecture has attracted significant attention recently. It can be stated as inequalities on the potential of a scalar field which is conjectured to satisfy certain constraints. In this work, we discuss the theoretical viability of deformed Starobinsky gravity in light of the refined swampland conjectures. We consider the deformation of the form [Formula: see text] with [Formula: see text] being a constant. We then constrain [Formula: see text] using the spectral index of curvature perturbation [Formula: see text] and the tensor-to-scalar ratio [Formula: see text]. We demonstrate that the model under consideration is in strong tension with the refined swampland conjecture. However, regarding our analysis with proper choices of parameters [Formula: see text] and [Formula: see text], we discover that the model can always satisfy this new refined swampland conjecture. Therefore, the model might be in “landscape” since the “further refining de Sitter swampland conjecture” is satisfied.