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Figure 3: Spectrum of left-invariant modes of the solutions onSp(2)
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S(U(2)×U(1))andSU(3)
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U(1)×U(1).
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expansion forms can then be chosen to bethe same as the Y(2−)
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iof [14]. Furthermore, there
|
is one tensor multiplet, which contains the dilaton Φ, the tw o-formBµνand two axions ξ
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and˜ξcoming from the expansion of the RR-potential C3:
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C3=ξα+˜ξβ, (4.3)
|
where a choice for αandβspanning the left-invariant three-forms would be Y(3−)and
|
Y(3+)of [14] respectively. In the presence of Romans mass or ˆF2-flux the two-form Bµν
|
becomes massive and cannot be dualized to a scalar. The dilat on and˜ξappear in a chiral
|
multiplet of the complex moduli sector of the N= 1 theory, while Bµνandξare projected
|
out by the orientifold. By using the N= 1 approach we thus loose the information on just
|
one scalarξ. A proper N= 2 analysis would however learn that ξdoes not appear in the
|
scalarpotential (seee.g.[36]), implyingthatitismassle ssandthusabovetheBreitenlohner-
|
Freedman bound. Moreover, the scalar potential should be th e same whether it is obtained
|
directly from reducing the 10D supergravity action (as in [5 9]) or whether it is obtained
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usingN= 2 orN= 1 technology8. Furthermore we note that the massless scalar field ξ
|
not appearing in the potential is not a modulus, since it is ch arged [60, 61], and therefore
|
eaten by a vector field becoming massive.
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Thespectraof left-invariant modesforSp(2)
|
S(U(2)×U(1))andSU(3)
|
U(1)×U(1)aredisplayed infigure
|
3. The Breitenlohner-Freedman bound is indicated as a horiz ontal dashed line. The Sp(2)-
|
model has six scalar fluctuations entering the potential: ki,biwithi= 1,2 from the two
|
vector multiplets, and Φ ,˜ξfrom the universal hypermultiplet, while the SU(3)-model h as
|
two more fluctuations from the extra vector multiplet. These two extra modes make a big
|
difference for the stability analysis since one of them tends t o be below the Breitenlohner-
|
Freedman bound for the purple and dark green solution. As a re sult, even though the
|
solutions for the Sp(2)- and SU(3)-model take the same form, the SU(3)-model has more
|
unstable solutions: compare figure 1 and 4.
|
8The only potential difference between the latter two would be the contribution from the orientifold.
|
We have checked that this contribution vanishes in the scala r potentials of [14] in the limit of the orientifold
|
chargeµ→0.
|
– 13 –Figure 4:SU(3)
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U(1)×U(1)-model: plot of aR4Din terms of the shape parameter σ. Unstable solutions
|
are indicated in red.
|
Inparticular, wenotethatthereductionoftheEnglert-typ esolutionisunstablefor σ=
|
2 in the Sp(2)-model, in agreement with [38], since the M-the ory lift of the corresponding
|
supersymmetric solution has eight Killing spinors. We inde ed find the same negative mass-
|
squaredM2=−(4/5)|Λ|for the unstable mode as in that paper. On the other hand,
|
forσ= 2/5 the Englert-type solution is stable against left-invaria nt fluctuations. This is
|
still in agreement with [38] which relied on the existence of at least two Killing spinors,
|
while the M-theory lift of the N= 1 supersymmetric solution at σ= 2/5 has only one
|
Killing-spinor. For the SU(3)-model, all Englert-type sol utions turn out to be unstable
|
(including the ones outside the condition (3.10)).
|
We also investigated the stability of the additional soluti ons at the special point σ= 2
|
found in [37]. We found that for the Sp(2)-model all these sol utions are stable against left-
|
invariant fluctuations. For the SU(3)-model on theother han dit turnsout that thediscrete
|
solutions ineqs.(3.16) and(3.17) ofthatreferenceareuns table, whilethecontinuous family
|
of eq. (3.18) becomes unstable for
|
γ2
|
β2>5(75∓16√
|
21)
|
8217, (4.4)
|
for the±sign choice in front of the square root in eq. (3.18) of that pa per respectively
|
(note that the supersymmetric solution corresponds to the p ointγ2/β2= 0 in this family).
|
Finally, we note that generically (i.e. unless an eigenvalu e is crossing zero at a special
|
value forσ) all the plotted modes are massive. For a range of values for σone of the
|
eigenvalues for the dark green and purple solution takes a sm all, but still non-zero value.
|
– 14 –5. Conclusions
|
In this paper we presented new families of non-supersymmetr ic AdS 4vacua. In fact,
|
extrapolating from our analysis on these specific coset mani folds and under the assumption
|
that a proper treatment of flux quantization does not kill muc h more vacua than in the
|
supersymmetric case, it would seem that there are more of the se non-supersymmetric
|
vacua than supersymmetric ones. This would imply that such v acua cannot be ignored
|
in landscape studies. We have moreover shown that many of the m are stable against a
|
specific set of fluctuations, namely the ones that can be expan ded in terms of left-invariant
|
forms. If these vacua turn out to be stable against all fluctua tions they should also have
|
a CFT-dual, which could be studied along the lines of [20], wh ere the three-dimensional
|
Chern-Simons-matter theory dual to a particular highly sym metric non-supersymmetric
|
vacuum was proposed. Furthermore, the nice property of some IIA vacua that all moduli
|
enter the superpotential and thus can be stabilized at a clas sical level [15] also extends to
|
our non-supersymmetric vacua.
|
A next step would be to relax the constraint that the solution s should have the same
|
geometry as the supersymmetric solution. It is also interes ting to investigate whether a
|
similar ansatz and techniques can be used to look for tree-le vel dS-vacua [62].
|
Acknowledgments
|
We thank Davide Cassani for useful email correspondence and proofreading, and further-
|
more Claudio Caviezel for active discussions and initial co llaboration. We would further
|
like to thank the Max-Planck-Institut f¨ ur Physik in Munich , where both of the authors
|
were affiliated during the bulk of the work on this paper. P.K. i s a Postdoctoral Fellow
|
of the FWO – Vlaanderen. The work of P.K. is further supported in part by the FWO –
|
Vlaanderen project G.0235.05 and in part by the Federal Office for Scientific, Technical and
|
Cultural Affairs through the ’Interuniversity Attraction Po les Programme Belgian Science
|
Policy’ P6/11-P. S.K. is supported by the SFB – Transregio 33 “The Dark Universe” by
|
the DFG.
|
A. SU(3)-structure
|
A real non-degenerate two-form Jand a complex decomposable three-form Ω define an
|
SU(3)-structure on the 6D manifold M6iff:
|
Ω∧J= 0, (A.1a)
|
Ω∧¯Ω =8i
|
3!J∧J∧J∝negationslash= 0, (A.1b)
|
and the associated metric is positive-definite. This metric is determined by Jand Ω as
|
follows:
|
gmn=−JmpIpn, (A.2)
|
withIthe complex structure associated (in the way of [63]) to Ω. Th e volume-form is
|
given by vol 6=1
|
3!J3=−(i/8)Ω∧¯Ω.
|
– 15 –Theintrinsictorsionofthemanifold M6decomposesintofivetorsionclasses W1,...,W5.
|
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