scholarly journals MODULI STABILIZATION IN STRINGY ISS MODELS

2008 ◽  
Vol 23 (14n15) ◽  
pp. 2190-2191
Author(s):  
MASAHITO YAMAZAKI
Keyword(s):  
Cosmological Constant ◽  
Susy Breaking ◽  
Fine Tuning ◽  
De Sitter ◽  
Moduli Stabilization ◽  
De Sitter Vacua

We present a stringy realization of the ISS metastable SUSY breaking model with moduli stabilization. The mass moduli of the ISS model is stabilized by gauging of a U(1) symmetry and its D-term potential. The SUSY is broken both by F-terms and D-terms. It is possible to obtain de-Sitter vacua with a vanishingly small cosmological constant by an appropriate fine-tuning of flux parameters. The content of this article is based on our recent paper1, which is in collaboration with Yu Nakayama (Berkeley) and Tsutomu Yanagida (Tokyo).

scholarly journals Cosmological model favored by the holographic principle

2016 ◽  
Vol 41 ◽  
pp. 1660127
Author(s):  
Irina Dymnikova ◽  
Anna Dobosz ◽  
Bożena Sołtysek
Keyword(s):  
Cosmological Model ◽  
Cosmological Constant ◽  
Space Time ◽  
Holographic Principle ◽  
Einstein Equations ◽  
Energy Tensor ◽  
De Sitter ◽  
Quantum Evaporation ◽  
Stress Energy ◽  
De Sitter Vacua

We present a regular spherically symmetric cosmological model of the Lemaitre class distinguished by the holographic principle as the thermodynamically stable end-point of quantum evaporation of the cosmological horizon. A source term in the Einstein equations connects smoothly two de Sitter vacua with different values of cosmological constant and corresponds to anisotropic vacuum dark fluid defined by symmetry of its stress-energy tensor which is invariant under the radial boosts. Global structure of space-time is the same as for the de Sitter space-time. Cosmological evolution goes from a big initial value of the cosmological constant towards its presently observed value.

scholarly journals Axion hilltops, Kahler modulus quintessence and the swampland criteria

2019 ◽  
Vol 34 (28) ◽  
pp. 1950164 ◽  
Author(s):  
Maxim Emelin ◽  
Radu Tatar
Keyword(s):  
Degrees Of Freedom ◽  
Initial Conditions ◽  
Effective Field ◽  
Fine Tuning ◽  
De Sitter ◽  
Moduli Stabilization ◽  
Nonperturbative Effect ◽  
Initial Conditions Problem ◽  
Field Excursion ◽  
Hubble Time

We study the interplay among extrema of axion potentials, Kahler moduli stabilization and the swampland criteria. We argue that moving away from the minima of nonperturbatively generated axion potentials can lead to a runaway behavior of moduli that govern the couplings in the effective field theory. The proper inclusion of these degrees of freedom resolves the conflict between periodic axion potentials and the gradient de Sitter criterion, without the need to invoke the refined de Sitter criterion. We investigate the possibility of including this runaway direction as a model of quintessence that satisfies the swampland criteria. Using a single nonperturbative effect, the maximum along the axion direction provides such a runaway direction, which is unstable in the axion directions, sensitive to initial conditions and too steep to allow for a Hubble time of expansion without violating the field excursion criterion. Adding a second nonperturbative effect generates a saddle point in the potential satisfying the refined de Sitter criterion, which solves the steepness problem and improves the initial conditions problem although some fine-tuning remains required.

scholarly journals Cosmological Constant in SUGRA Models with Degenerate Vacua

Universe ◽  
2019 ◽  
Vol 5 (10) ◽  
pp. 214
Author(s):  
Colin Froggatt ◽  
Holger Nielsen ◽  
Roman Nevzorov ◽  
Anthony Thomas
Keyword(s):  
Energy Density ◽  
Cosmological Constant ◽  
Scalar Potential ◽  
Planck Scale ◽  
Susy Breaking ◽  
Fine Tuning ◽  
Tree Level ◽  
Vacuum Energy Density ◽  
Multiple Point ◽  
Dark Energy Density

The extrapolation of couplings up to the Planck scale within the standard model (SM) indicates that the Higgs effective potential can have two almost degenerate vacua, which were predicted by the multiple point principle (MPP). The application of the MPP to ( N = 1 ) supergravity (SUGRA) implies that the SUGRA scalar potential of the hidden sector possesses at least two exactly degenerate minima. The first minimum is associated with the physical phase in which we live. In the second supersymmetric (SUSY) Minkowski vacuum, the local SUSY may be broken dynamically, inducing a tiny vacuum energy density. In this paper, we consider the no-scale-inspired SUGRA model in which the MPP conditions are fulfilled without any extra fine-tuning at the tree-level. Assuming that at high energies, the couplings in both phases are identical, one can estimate the dark energy density in these vacua. Using the two-loop renormalization group (RG) equations, we find that the measured value of the cosmological constant can be reproduced if the SUSY breaking scale M S in the physical phase is of the order of 100 TeV. The scenario with the Planck scale SUSY breaking is also discussed.

scholarly journals The tadpole problem

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Iosif Bena ◽  
Johan Blåbäck ◽  
Mariana Graña ◽  
Severin Lüst
Keyword(s):  
Moduli Space ◽  
Complex Structure ◽  
De Sitter ◽  
Generic Point ◽  
Cancellation Condition ◽  
Moduli Stabilization ◽  
Induced Charge ◽  
De Sitter Vacua ◽  
Breaking Scale ◽  
Rule Out

Abstract We examine the mechanism of moduli stabilization by fluxes in the limit of a large number of moduli. We conjecture that one cannot stabilize all complex-structure moduli in F-theory at a generic point in moduli space (away from singularities) by fluxes that satisfy the bound imposed by the tadpole cancellation condition. More precisely, while the tadpole bound in the limit of a large number of complex-structure moduli goes like 1/4 of the number of moduli, we conjecture that the amount of charge induced by fluxes stabilizing all moduli grows faster than this, and is therefore larger than the allowed amount. Our conjecture is supported by two examples: K3 × K3 compactifications, where by using evolutionary algorithms we find that moduli stabilization needs fluxes whose induced charge is 44% of the number of moduli, and Type IIB compactifications on $$ \mathbbm{CP} $$ CP 3, where the induced charge of the fluxes needed to stabilize the D7-brane moduli is also 44% of the number of these moduli. Proving our conjecture would rule out de Sitter vacua obtained via antibrane uplift in long warped throats with a hierarchically small supersymmetry breaking scale, which require a large tadpole.

scholarly journals LOCALIZATION OF GRAVITY IN BRANE WORLD COSMOLOGIES

2003 ◽  
Vol 18 (14) ◽  
pp. 983-992 ◽  
Author(s):  
PARAMPREET SINGH ◽  
NARESH DADHICH
Keyword(s):  
Cosmological Constant ◽  
Bound State ◽  
Cosmological Models ◽  
Brane World ◽  
Fine Tuning ◽  
Expanding Universe ◽  
De Sitter ◽  
Positive Cosmological Constant ◽  
Zero Mass ◽  
Bulk Parameters

The most remarkable and interesting feature of brane world scenario is the use of bulk's curvature to localize gravity on the brane, albeit with fine tuning of the brane and bulk parameters. For FRW expanding universe on the brane, it is a moving hypersurface in Schwarzschild anti de Sitter bulk spacetime. We show that zero mass gravitons have bound state on the brane for suitable values of brane and bulk parameters. There occur various cases giving rise to different cosmological models, in particular we discuss a model with positive cosmological constant on the brane.

scholarly journals MINKOWSKI BRANE IN ASYMPTOTIC dS5 SPACETIME WITHOUT FINE-TUNING

2004 ◽  
Vol 19 (19) ◽  
pp. 1447-1451 ◽  
Author(s):  
ZHE CHANG ◽  
SHAO-XIA CHEN ◽  
XIN-BING HUANG
Keyword(s):  
Cosmological Constant ◽  
Minkowski Spacetime ◽  
Fine Tuning ◽  
Dimensional Manifold ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Positive Cosmological Constant ◽  
Coordinate Axis ◽  
Sitter Spacetime

We discuss properties of a three-brane in an asymptotic five-dimensional de Sitter spacetime. It is found that a Minkowski solution can be obtained without fine-tuning. In the model, the tiny observed positive cosmological constant is interpreted as a curvature of five-dimensional manifold, but the Minkowski spacetime, where we live, is a natural three-brane perpendicular to the fifth coordinate axis.

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