dS Minimum Research Articles

High-Success-Rate and Fast ISAR Imaging of Nonstationary Moving Platform-Attitude Rapidly Changing Ship Target With DS Evidence and Minimum Entropy Theory

High-Success-Rate and Fast ISAR Imaging of Nonstationary Moving Platform-Attitude Rapidly Changing Ship Target With DS Evidence and Minimum Entropy Theory

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.

Revisiting oscillon formation in the Kachru-Kallosh-Linde-Trivedi scenario

KKLT scenario has succeeded in stabilizing the volume modulus and constructing metastable de Sitter (dS) vacua in type IIB string theory. We revisit to investigate the possibility of the oscillon (or I-ball) formation in the KKLT scenario when the volume modulus is initially displaced from the dS minimum. Special attention is paid to physically realistic initial conditions of the volume modulus, which was not taken in the literature. Using lattice simulations, we find that oscillons do not form unless the volume modulus is initially placed at very near the local maximum, which requires severe fine-tuning.

Mass production of IIA and IIB dS vacua

We describe several applications of the mass production procedure proposed in [1] to stabilize multiple moduli in a dS vacuum, in supergravity models inspired by string theory. The construction involves a small downshift of an initial supersymmetric Minkowski minimum to a supersymmetric AdS minimum, and a consequent small uplift to a dS minimum. Our type IIA examples include dS stabilization in a 7-moduli model with [SL(2, ℝ)]7 tree level symmetry, and its simplified version, a 3-moduli STU model. In these models, we use uplifting anti-D6 branes. In type IIB models, we present 2- and 3-moduli examples of stable dS vacua in CY three-folds, with an uplifting anti-D3 brane. These include K3 fibration models, a CICY model and a multi-hole Swiss cheese model. We also address the issue whether this procedure is limited to a very small parameter range or if large deviations from the progenitor Minkowski vacuum are possible.

Modular symmetries and the swampland conjectures

Recent string theory tests of swampland ideas like the distance or the dS conjectures have been performed at weak coupling. Testing these ideas beyond the weak coupling regime remains challenging. We propose to exploit the modular symmetries of the moduli effective action to check swampland constraints beyond perturbation theory. As an example we study the case of heterotic 4d mathcal{N}=1 compactifications, whose non-perturbative effective action is known to be invariant under modular symmetries acting on the Kähler and complex structure moduli, in particular SL(2, Z) T-dualities (or subgroups thereof) for 4d heterotic or orbifold compactifications. Remarkably, in models with non-perturbative superpotentials, the corresponding duality invariant potentials diverge at points at infinite distance in moduli space. The divergence relates to towers of states becoming light, in agreement with the distance conjecture. We discuss specific examples of this behavior based on gaugino condensation in heterotic orbifolds. We show that these examples are dual to compactifications of type I’ or Horava-Witten theory, in which the SL(2, Z) acts on the complex structure of an underlying 2-torus, and the tower of light states correspond to D0-branes or M-theory KK modes. The non-perturbative examples explored point to potentials not leading to weak coupling at infinite distance, but rather diverging in the asymptotic corners of moduli space, dynamically forbidding the access to points with global symmetries. We perform a study of general modular invariant potentials and find that there are dS maxima and saddle points but no dS minima, and that all examples explored obey the refined dS conjecture.

Swampland variations on a theme by KKLT

The KKLT scenario in a warped throat, if consistent, provides a concrete counterexample to both the AdS scale separation and the dS swampland conjectures. First, we define and analyze the relevant effective field theory for the conifold modulus and the overall Kähler modulus that both have exponentially small masses. The scalar potential still admits KKLT-like AdS and dS minima. Second, we critically analyze the reliability of the employed Wilsonian effective action by evaluating the masses of light modes localized in the warped throat. The resulting mass spectrum is discussed with respect to the swampland distance conjecture. We find the recently observed emergent nature of the latter not only at large distance points but also at the conifold point motivating a general extension of it. In this respect, KKLT and trans-Planckian field distance are on equal footing. It is pointed out that the reliability of the KKLT minimum will depend on how this emergent behavior is interpreted.

Perturbative stability along the supersymmetric directions of the landscape

We consider the perturbative stability of non-supersymmetric configurations in \U0001d4a9=1 supergravity models with a spectator sector not involved in supersymmetry breaking. Motivated by the supergravity description of complex structure moduli in Large Volume Compactifications of type IIB-superstrings, we concentrate on models where the interactions are consistent with the supersymmetric truncation of the spectator fields, and we describe their couplings by a random ensemble of generic supergravity theories. We characterise the mass spectrum of the spectator fields in terms of the statistical parameters of the ensemble and the geometry of the scalar manifold. Our results show that the non-generic couplings between the spectator and the supersymmetry breaking sectors can stabilise all the tachyons which typically appear in the spectator sector before including the supersymmetry breaking effects, and we find large regions of the parameter space where the supersymmetric sector remains stable with probability close to one. We discuss these results about the stability of the supersymmetric sector in two physically relevant situations: non-supersymmetric Minkowski vacua, and slow-roll inflation driven by the supersymmetry breaking sector. For the class of models we consider, we have reproduced the regimes in which the KKLT and Large Volume Scenarios stabilise all supersymmetric moduli. We have also identified a new regime in which the supersymmetric sector is stabilised at a very robust type of dS minimum without invoking a large mass hierarchy.

The scale of inflation in the landscape

We determine the frequency of regions of small-field inflation in the Wigner landscape as an approximation to random supergravities/type IIB flux compactifications. We show that small-field inflation occurs exponentially more often than large-field inflation. The power of primordial gravitational waves from inflation is generically tied to the scale of inflation. As for small-field models this is below observational reach, their exponential enhancement seems to indicate a tendency towards small tensor-to-scalar ratio r. However, cosmologically viable inflationary regions must provide for a successful exit from inflation into a meta-stable dS minimum. Hence future work will need to determine the ‘graceful exit likelihood’ before any statement about the statistically expected level of tensor modes r is possible.

AdS cycles in eternally inflating background

In the eternally inflating background, the bubbles with AdS vacua will crunch. However, this crunch might be followed by a bounce. It is generally thought that the bubble universe may be cyclic, which will go through a sequence of AdS crunches, until the field inside the bubble finally lands at a dS minimum. However, we show that due to the amplification of field fluctuation, the bubble universe going through AdS cycles will inevitably fragment within two or three cycles. We discuss its implication to the eternal inflation scenario.

Explicit de Sitter flux vacua for global string models with chiral matter

We address the open question of performing an explicit stabilisation of all closed string moduli (including dilaton, complex structure and Kaehler moduli) in fluxed type IIB Calabi-Yau compactifications with chiral matter. Using toric geometry we construct Calabi-Yau manifolds with del Pezzo singularities. D-branes located at such singularities can support the Standard Model gauge group and matter content. In order to control complex structure moduli stabilisation we consider Calabi-Yau manifolds which exhibit a discrete symmetry that reduces the effective number of complex structure moduli. We calculate the corresponding periods in the symplectic basis of invariant three-cycles and find explicit flux vacua for concrete examples. We compute the values of the flux superpotential and the string coupling at these vacua. Starting from these explicit complex structure solutions, we obtain AdS and dS minima where the Kaehler moduli are stabilised by a mixture of D-terms, non-perturbative and perturbative alpha'-corrections as in the LARGE Volume Scenario. In the considered example the visible sector lives at a dP_6 singularity which can be higgsed to the phenomenologically interesting class of models at the dP_3 singularity.

ON ISSUES IN SWISS CHEESE COMPACTIFICATIONS

We give a brief review of our previous works.1,2 We discuss two sets of issues. The first has to do with the possibility of getting a non-supersymmetric dS minimum without the addition of [Formula: see text]-branes as in KKLT, and axionic slow-roll inflation, in type II flux compactifications. The second has to do with the "Inverse Problem"3 and "Fake Superpotentials"4 for extremal (non)supersymmetric black holes in type II compactifications. We use (orientifold of) a "Swiss Cheese" Calabi–Yau5 expressed as a degree-18 hypersurface in WCP4[1, 1, 1, 6, 9] in the "large-volume-scenario" limit6 for the former.

Dynamics ofD3-D7 brane inflation in throats

Dynamics of D3-branes in models of warped D3-D7 inflationary set up is studied where perturbative α' correction to the Kahler potential and the nonperturbative corrections to the superpotential are included. It is shown that a dS minimum can be obtained without introducing anti-branes. Some specific configurations of D7-branes embedding were studied. After stabilizing the angular directions, it is shown that the resulting D3-D7 potential of the radial position of the D3-brane is too steep to allow slow-roll inflation. Depending on D7-branes embedding and the stabilized angular directions, the mobile D3-brane can move either towards the tip of the throat or towards the D7-branes.

“Finite” non-Gaussianities and tensor–scalar ratio in large volume Swiss-cheese compactifications

Developing on the ideas of (Section 4 of) [A. Misra, P. Shukla, Moduli stabilization, large-volume dS minimum without anti- D3-branes, (non-)supersymmetric black hole attractors and two-parameter Swiss cheese Calabi–Yau's, Nucl. Phys. B 799 (2008) 165–198, arXiv: 0707.0105] and [A. Misra, P. Shukla, Large volume axionic Swiss-cheese inflation, Nucl. Phys. B 800 (2008) 384–400, arXiv: 0712.1260 [hep-th]] and using the formalisms of [S. Yokoyama, T. Suyama, T. Tanaka, Primordial non-Gaussianity in multi-scalar slow-roll inflation, arXiv: 0705.3178 [astro-ph]; S. Yokoyama, T. Suyama, T. Tanaka, Primordial non-Gaussianity in multi-scalar inflation, Phys. Rev. D 77 (2008) 083511, arXiv: 0711.2920 [astro-ph]], after inclusion of perturbative and non-perturbative α ′ corrections to the Kähler potential and ( D1- and D3-)instanton generated superpotential, we show the possibility of getting finite values for the non-linear parameter f NL while looking for non-Gaussianities in type IIB compactifications on orientifolds of the Swiss cheese Calabi–Yau WCP 4 [ 1 , 1 , 1 , 6 , 9 ] in the L(arge) V(olume) S(cenarios) limit. We show the same in two contexts. First is multi-field slow-roll inflation with D3-instanton contribution coming from a large number of multiple wrappings of a single (Euclidean) D3-brane around the “small” divisor yielding f NL ∼ O ( 1 ) . The second is when the slow-roll conditions are violated and for the number of the aforementioned D3-instanton wrappings being of O ( 1 ) but more than one, yielding f NL ∼ O ( 1 ) . Based on general arguments not specific to our (string-theory) set-up, we argue that requiring curvature perturbations not to grow at horizon crossing and at super-horizon scales, automatically picks out hybrid inflationary scenarios which in our set up can yield f NL ∼ O ( 1 ) and tensor–scalar ratio of O ( 10 −2 ) . For all our calculations, the world-sheet instanton contributions to the Kähler potential coming from the non-perturbative α ′ corrections, are restricted to appropriate choices of the degrees of genus-zero rational curves that correspond to very large values of Gopakumar–Vafa invariants for the chosen compact projective variety. To our knowledge, such values of non-Gaussianities and tensor–scalar ratio in slow-roll inflationary and/or slow-roll violating scenarios, have been obtained for the first time from string theory. We also make some observations pertaining to the possibility of the axionic inflaton also being a cold dark matter candidate as well as a quintessence field used for explaining dark energy. Our calculations predict, however, loss of scale invariance of the spectral index of curvature perturbations beyond the existing experimental bounds if one requires “freeze-out” of curvature perturbations at horizon crossing and super-horizon scales. The violation of scale invariance is within experimental bounds if the freeze-out is required only at super-horizon scales—in such scenarios, one can get f NL ∼ O ( 1 ) and r ∼ 10 −2 .

Finite temperature behaviour of O'KKLT model

AbstractWe summarize our work on the O'Raifeartaigh uplifted KKLT model at finite temperature. We study the system for parameter values for which the zero temperature potential for the volume modulus has a dS minimum. The temperature‐dependent part of the effective potential has a runaway behaviour for one exponent in the superpotential, whereas it can have local minima at finite field vevs for two exponents in the superpotential. However, it turns out that, despite the presence of those minima, the zero temperature dS vacuum is not destabilized by thermal corrections within the whole range of validity of our approximations.

O'KKLT at finite temperature

We study whether finite temperature corrections decompactify the internal space in KKLT compactifications with an uplifting sector given by a system that exhibits metastable dynamical supersymmetry breaking. More precisely, we calculate the one-loop temperature corrections to the effective potential of the volume modulus in the KKLT model coupled to the quantum corrected O'Raifeartaigh model. We prove that for the original KKLT model, namely with one exponent in the non-perturbative superpotential, the finite temperature potential is runaway when at zero temperature there is a dS minimum. On the other hand, for a non-perturbative superpotential of the race-track type with two exponents, we demonstrate that the temperature-dependent part of the effective potential can have local minima at finite field vevs. However, rather unexpectedly, it turns out that these minima do not affect the structure of the full effective potential and so the volume modulus is stabilized at the local minimum of the zero temperature potential for the whole range of validity of the supergravity approximation.

Large volume axionic Swiss cheese inflation

Continuing with the ideas of (Section 4 of) [A. Misra, P. Shukla, Moduli stabilization, large-volume dS minimum without anti-D3-branes, (non-)supersymmetric black hole attractors and two-parameter Swiss cheese Calabi–Yau's, arXiv: 0707.0105 [hep-th], Nucl. Phys. B, in press], after inclusion of perturbative and non-perturbative α ′ corrections to the Kähler potential and (D1- and D3-) instanton generated superpotential, we show the possibility of slow roll axionic inflation in the large volume limit of Swiss cheese Calabi–Yau orientifold compactifications of type IIB string theory. We also include one- and two-loop corrections to the Kähler potential but find the same to be subdominant to the (perturbative and non-perturbative) α ′ corrections. The NS–NS axions provide a flat direction for slow roll inflation to proceed from a saddle point to the nearest dS minimum.

Moduli stabilization, large-volume dS minimum without [formula omitted]-branes, (non-)supersymmetric black hole attractors and two-parameter Swiss cheese Calabi–Yau's

We consider two sets of issues in this paper. The first has to do with moduli stabilization, existence of “area codes” [A. Giryavets, New attractors and area codes, JHEP 0603 (2006) 020, hep-th/0511215] and the possibility of getting a non-supersymmetric dS minimum without the addition of D 3 ¯ -branes as in KKLT for type II flux compactifications. The second has to do with the “inverse problem” [K. Saraikin, C. Vafa, Non-supersymmetric black holes and topological strings, hep-th/0703214] and “fake superpotentials” [A. Ceresole, G. Dall'Agata, Flow equations for non-BPS extremal black holes, JHEP 0703 (2007) 110, hep-th/0702088] for extremal (non-)supersymmetric black holes in type II compactifications. We use (orientifold of) a “Swiss cheese” Calabi–Yau [J.P. Conlon, F. Quevedo, K. Suruliz, Large-volume flux compactifications: Moduli spectrum and D3/D7 soft supersymmetry breaking, JHEP 0508 (2005) 007, hep-th/0505076] expressed as a degree-18 hypersurface in WCP 4 [ 1 , 1 , 1 , 6 , 9 ] in the “large-volume-scenario” limit [V. Balasubramanian, P. Berglund, J.P. Conlon, F. Quevedo, Systematics of moduli stabilisation in Calabi–Yau flux compactifications, JHEP 0503 (2005) 007, hep-th/0502058]. The main result of our paper is that we show that by including non-perturbative α ′ and instanton corrections in the Kähler potential and superpotential [T.W. Grimm, Non-perturbative corrections and modularity in N = 1 type IIB compactifications, arXiv: 0705.3253 [hep-th]], it may be possible to obtain a large-volume non-supersymmetric dS minimum without the addition of anti-D3 branes a la KKLT. The chosen Calabi–Yau has been of relevance also from the point of other studies of Kähler moduli stabilization via non-perturbative instanton contributions [F. Denef, M.R. Douglas, B. Florea, Building a better racetrack, JHEP 0406 (2004) 034, hep-th/0404257] and non-supersymmetric AdS vacua (and their subsequent dS-uplifts) using ( α ′ ) 3 corrections to the Kähler potential [V. Balasubramanian, P. Berglund, J.P. Conlon, F. Quevedo, Systematics of moduli stabilisation in Calabi–Yau flux compactifications, JHEP 0503 (2005) 007, hep-th/0502058; K. Becker, M. Becker, M. Haack, J. Louis, Supersymmetry breaking and alpha'-corrections to flux induced potentials, JHEP 0206 (2002) 060, hep-th/0204254; A. Westphal, de Sitter string vacua from Kähler uplifting, JHEP 0703 (2007) 102, hep-th/0611332; V. Balasubramanian, P. Berglund, Stringy corrections to Kähler potentials, SUSY breaking, and the cosmological constant problem, JHEP 0411 (2004) 085, hep-th/0408054].

Lifetime of stringy de Sitter vacua

In this note we perform a synopsis of the life-times from vacuum decay of several de Sitter vacuum constructions in string/M-theory which have a single dS minimum arising from lifting a pre-existing AdS extremum and no other local minima existent after lifting. For these vacua the decay proceeds via a Coleman-De Luccia instanton towards the universal Minkowski minimum at infinite volume. This can be calculated using the thin-wall approximation, provided the cosmological constant of the local dS minimum is tuned sufficiently small. We compare the estimates for the different model classes and find them all stable in the sense of exponentially long life times as long as they have a very small cosmological constant and a scale of supersymmetry breaking TeV.

O'KKLT

We propose to combine the quantum corrected O'Raifeartaigh model, which has a dS minimum near the origin of the moduli space, with the KKLT model with an AdS minimum. The combined effective N=1 supergravity model, which we call O'KKLT, has a dS minimum with all moduli stabilized. Gravitino in the O'KKLT model tends to be light in the regime of validity of our approximations. We show how one can construct models with a light gravitino and a high barrier protecting vacuum stability during the cosmological evolution.

DD¯dark energy in string warped compactification

We study the evolution of relic D3-branes after the $\mathrm{D}3/\overline{\mathrm{D}3}$-brane inflation in string warped compactification. The motion of D3-branes can be frozen under certain conditions during the radiation/matter domination. These D3-branes cannot be released until the $\mathrm{D}3/\overline{\mathrm{D}3}$-branes potential energy becomes dominated at late time. Subsequently, they will move towards to $\overline{\mathrm{D}3}$-branes, which play the role of uplifting AdS minimum to dS minimum, near the apex of throats. The annihilation of $\mathrm{D}3/\overline{\mathrm{D}3}$-branes leads to the disappearance of dS vacua. This process may be regarded as a rapid decay channel of present dS vacua. We discuss the parameter spaces required by this process and calculate the decay time.