A George Bernard Shaw Quote

  “Never wrestle with pigs. You both get dirty and the pig likes it.”

Karan Thapar Interview Fareed Zakaria on Ukraine War

 TO very intelligent people discussing the hottest topic of the day here.

Imran Khan and UN Resolution Against Islamophobia

 In this rally snippet Imran Khan wipes the floor with Maulana Fazlur Rahman in the context of the resolution passed a day or so before in the UN againt Islamophobia.

Phenomenology with String Lanscape

 Some people have the view that string theory has no de Sitter vacua, let alone an astronomical number. I have been posting on this issue. I intend to do that further. In the meantime there are papers that are going ahead with string theory phenomenology. The paper with the following abstract also does that.

String Landscape and Fermion Masses

Stefano Andriolo, Shing Yan Li, S.-H. Henry Tye

Besides the string scale, string theory has no parameter except some quantized flux values; and the string theory Landscape is generated by scanning over discrete values of all the flux parameters present. We propose that a typical (normalized) probability distribution P(Q) of a physical quantity Q (with nonnegative dimension) tends to peak (diverge) at Q=0 as a signature of string theory. In the Racetrack Kähler uplift model, where P(Λ) of the cosmological constant Λ peaks sharply at Λ=0, the electroweak scale (not the electroweak model) naturally emerges when the median Λ is matched to the observed value. We check the robustness of this scenario. In a bottom-up approach, we find that the observed quark and charged lepton masses are consistent with the same probabilistic philosophy, with distribution P(m) that diverges at m=0, with the same (or almost the same) degree of divergence. This suggests that the Standard Model has an underlying string theory description, and yields relations among the fermion masses, albeit in a probabilistic approach (very different from the usual sense). Along this line of reasoning, the normal hierarchy of neutrino masses is clearly preferred over the inverted hierarchy, and the sum of the neutrino masses is predicted to be ∑mν≃0.0592 eV, with an upper bound ∑mν<0.066 eV. This illustrates a novel way string theory can be applied to particle physics phenomenology.

 

Reservations About KKLT

 Paper with the following abstract still has some reservations about KKLT.

Gaugino condensation and small uplifts in KKLT

Federico Carta, Jakob Moritz, Alexander Westphal

In the first part of this note we argue that ten dimensional consistency requirements in the form of a certain tadpole cancellation condition can be satisfied by KKLT type vacua of type IIB string theory. We explain that a new term of non-local nature is generated dynamically once supersymmetry is broken and ensures cancellation of the tadpole. It can be interpreted as the stress caused by the restoring force that the stabilization mechanism exerts on the volume modulus. In the second part, we explain that it is surprisingly difficult to engineer sufficiently long warped throats to prevent decompactification which are also small enough in size to fit into the bulk Calabi-Yau (CY). We give arguments that achieving this with reasonable amount of control may not be possible in generic CY compactifications while CYs with very non-generic geometrical properties might evade our conclusion.

Defending KKLT

 

The abstract of the paper with the following title does the defense.

 

Understanding KKLT from a 10d perspective

Yuta Hamada, Arthur Hebecker, Gary Shiu, Pablo Soler

Some of the most well-celebrated constructions of metastable de Sitter vacua from string theory, such as the KKLT proposal, involve the interplay of gaugino condensation on a D7-brane stack and an uplift by a positive tension object. These constructions have recently been challenged using arguments that rely on the trace-reversed and integrated 10d Einstein equation. We give a critical assessment of such concerns. We first relate an integrated 10d Einstein equation to the extremization condition for a 10d-derived 4d effective potential. Then we argue how to obtain the latter from a 10d action which incorporates gaugino condensation in a (recently proposed) manifestly finite, perfect-square form. This effective potential is consistent with 4d supergravity and does not present obstacles for an uplifted minimum. Moreover, within standard approximations, we understand the uplift explicitly in one of the popular versions of the integrated 10d equation. Our conclusion is that de Sitter constructions of the KKLT type cannot be dismissed simply based on the integrated 10d equations considered so far.

Distler on KKLT

 J. Distler wrote this post on the famous KKLT paper.

Though Distler does not completely clear KKLT but nevertheless he takes it positively.

The remark by Savdeep Sethi shows that he was among earlier critiques of KLT construction.

Another critic is Thomas van Riet.

In this paper I feel he looks like mitigated.

What are Flux Compactifications?

Following is the bibliographic discussion of Flux Compactification chapter of the the book Becker-Becker-Schwarz:

 

 

Flux compactications were introduced in Strominger (1986) and De Wit, Smit and Hari Dass (1987) as a generalization of conventional Calabi-Yau compactifications. Such compactifications include a warp factor, so that the ten-dimensional metric is no longer a direct product of the external and internal space-time. No-go theorems implied that in most cases such theories reduce to ordinary Calabi-Yau compactifications. However, with the development of non-perturbative string theory and M-theory, it became evident

that the no-go theorems could be circumvented. Flux compactifications were first studied in the context of M-theory in Becker and Becker (1996) and in the context of F-theory in Dasgupta, Rajesh and Sethi (1999). Giddings, Kachru and Polchinski (2002) explained how flux compactifications can give a large hierarchy of scales. Gra~na (2006) reviews flux compactifications. Gukov, Vafa and Witten (2001) made it evident that flux compactifications can lead to a solution of the moduli-space problem, since a non-vanishing

potential for the moduli fields is generated. This led to the introduction of the string theory landscape, which describes a huge number of possible string theory vacua, in Susskind (2003). Their properties were analyzed in Douglas (2003) using statistical methods. Flux compactifications are dual supergravity descriptions of conning gauge theories, as was pointed out in Klebanov and Strassler (2000) and Polchinski and Strassler (2000). The idea that a brane-world scenario provides an alternative to compactification was introduced in Randall and Sundrum (1999b).

The application of flux compactications to cosmology is an active area of research. Kachru, Kallosh, Linde and Trivedi (2003) discussed the construction of long-lived metastable de Sitter vacua, and Kachru, Kallosh, Linde, Maldacena, McAllister and Trivedi (2003) discussed the application to in-ation. Review articles on string cosmology include Linde (1999), Quevedo (2002) and Danielsson (2005).

Dasgupta-Rajesh-Sethi

The abstract of this paper is:

 

We study the properties of M and F theory compactifications to three and four dimensions with background fluxes. We provide a simple construction of supersymmetric vacua, including some with orientifold descriptions. These vacua, which have warp factors, typically have fewer moduli than conventional Calabi-Yau compactifications. The mechanism for anomaly cancellation in the orientifold models involves background RR and NS fluxes. We consider in detail an orientifold of K3×T2 with background fluxes. After a combination of T and S-dualities, this type IIB orientifold is mapped to a compactification of the SO(32) heterotic string on a non-Kahler space with torsion. 

 

***

Savdeep Sethi says on Distler's blog post :  I spent a great deal of time studying and constructing the first F-theory compactifications with flux (hep-th/9908088), and I am not sanguine (although I am still thinking about it).

Building a Better Racetrack

 This is the title of a DDF paper. 

 

The abstract reads:  We find IIb compactifications on Calabi-Yau orientifolds in which all Kahler moduli are stabilized, along lines suggested by Kachru, Kallosh, Linde and Trivedi. 

 

***

 

J Distler in his blog post said that this paper filled  one of the gaps in KKLT assertion.

Barren Lanscape

Robbins and Sethi wrote a paper critical of KKLT. The abstract read:

 

We consider the generation of a non-perturbative superpotential in F-theory compactifications with flux. We derive a necessary condition for the generation of such a superpotential in F-theory. For models with a single volume modulus, we show that the volume modulus is never stabilized by either abelian instantons or gaugino condensation. We then comment on how our analysis extends to a larger class of compactifications. From our results, it appears that among large volume string compactifications, metastable de Sitter vacua (should any exist) are non-generic.

KKLT Abstract

 We outline the construction of metastable de Sitter vacua of type IIB string theory. Our starting point is highly warped IIB compactifications with nontrivial NS and RR three-form fluxes. By incorporating known corrections to the superpotential from Euclidean D-brane instantons or gaugino condensation, one can make models with all moduli fixed, yielding a supersymmetric AdS vacuum. Inclusion of a small number of anti-D3 branes in the resulting warped geometry allows one to uplift the AdS minimum and make it a metastable de Sitter ground state. The lifetime of our metastable de Sitter vacua is much greater than the cosmological timescale of 10^10 years. We also prove, under certain conditions, that the lifetime of dS space in string theory will always be shorter than the recurrence time. 

 

Ref: Arxiv

Savdeep Sethi on KKLT (May 11, 2004)

There are no new ingredients involved in this proposal, only a new claim. The burden is to actually realize the claim.