Supersymmetric solitons in gauged N 8 supergravity Andr es Anabal on1 Antonio Gallerati2 Simon Ross3 Mario Trigiante24

2025-04-26 0 0 855.66KB 42 页 10玖币
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Supersymmetric solitons in gauged N= 8
supergravity
Andr´es Anabal´on1, Antonio Gallerati2, Simon Ross3, Mario Trigiante§2,4
1Departamento de Ciencias, Facultad de Artes Liberales, Universidad Adolfo Ib´a˜nez, Avenida
Diagonal las Torres 2640, Pe˜nalolen, Santiago, Chile
2Politecnico di Torino, Dipartimento di Scienza Applicata e Tecnologia, corso Duca degli Abruzzi 24,
10129 Torino, Italy
3Centre for Particle Theory, Department of Mathematical Sciences, Durham University, South Road,
Durham DH1 3LE, U.K.
4Istituto Nazionale di Fisica Nucleare, Sezione di Torino, via Pietro Giuria 1, 10125 Torino, Italy
Abstract
We consider soliton solutions in AdS4with a flat slicing and Wilson loops around
one cycle. We study the phase structure and find the ground state and identify
supersymmetric solutions as a function of the Wilson loops. We work in the context
of a scalar field truncation of gauged N= 8 supergravity, where all the dilatons
are equal and all the axions vanish in the STU model. In this theory, we construct
new soliton solutions parameterized by two Wilson lines. We find that there is a
degeneracy of supersymmetric solutions. We also show that, for alternate boundary
conditions, there exists a non-supersymmetric soliton solution with energy lower
than the supersymmetric one.
anabalo@gmail.com
antonio.gallerati@polito.it
simonfross@gmail.com
§mario.trigiante@polito.it
1
arXiv:2210.06319v2 [hep-th] 7 Feb 2023
Contents
1 Introduction and discussion 3
2 The model 5
2.1 Supersymmetry................................ 6
3 Hairy soliton solutions 9
3.1 Existenceofsolitons ............................. 11
3.2 Relation to earlier solutions . . . . . . . . . . . . . . . . . . . . . . . . . 15
4 Constant flux solutions 18
4.1 Quantizationofuxes ............................ 19
5 Supersymmetric solutions 20
5.1 Supersymmetric solutions with fixed fluxes . . . . . . . . . . . . . . . . . 22
5.2 Supersymmetric solutions with fixed charges . . . . . . . . . . . . . . . . 23
6 Phase structure 24
6.1 Euclideanaction ............................... 24
6.2 Fixed fluxes ψ1and ψ2............................ 25
6.3 Fixed qΛ.................................... 26
A Spinor conventions and SUSY for N= 2 models 33
B Analytic solutions for the fixed fluxes 35
C Global properties of the D= 11 background at radial infinity 35
D Remarks on the stability of the hairy soliton vs the AdS soliton at
fixed fluxes 37
References 39
2
1 Introduction and discussion
An interesting aspect of the AdS/CFT correspondence is the study of the possible
ground states as a function of the boundary conditions. The first non-trivial example
is the AdS soliton of [1], which is conjectured to correspond to the ground state of the
theory with a planar boundary, with one direction compactified on a circle with antiperi-
odic boundary conditions for fermions. In the present paper, we study generalizations
of the AdS soliton when we add Wilson loops for gauge fields around the circle.
We will work in the context of asymptotically AdS4solutions of a truncation of
N= 8 supergravity. Let us consider a representative of the conformal boundary of a
four-dimensional metric as
ds2
bound. =dt2+2+dz2,(1)
where ϕis a periodic coordinate. Fermions can be either periodic or anti-periodic around
the circle parametrized by ϕ. If fermions are anti-periodic, it is possible to construct an
interior solution where the vector ϕhas vanishing norm: this is the AdS soliton. One
might wonder what happens if extra sources are added to this configuration, like, for
instance, a Wilson loop
Φm=IAϕdϕ . (2)
In the following, we will consider the case of anti-periodic boundary conditions on the
ϕcircle, but periodic boundary conditions on the zcircle. As we will see, this allows
supersymmetric solitons for appropriate choices of Wilson loops; it also has the effect
of excluding the possibility of an AdS soliton solution where the zcircle contracts
smoothly in the interior. The relevant solutions will then either have both circles non-
contractible in the interior, or the ϕcircle contractible. The latter solutions, which
generalise the AdS soliton and can be obtained by double analytic continuation from
electrically charged black holes [112], are the main focus of our interest.
In the case of the simplest Einstein-Maxwell theory, the configuration has been
known for a while [13,14]. In [12] it was found that some of these configurations are
supersymmetric and that, at the supersymmetric point, there are two possible solutions,
the soliton and a Poincar´e-AdS solution dressed with a constant Wilson loop. In this
article, we extend this study to the case of gauged N= 8 supergravity, and construct
solutions of its STU model truncation in which the three dilatons are equal and all axions
vanish. In particular, we want to analyse whether the degeneracy of supersymmetric
solutions extends to this more general context.
In the pure Einstein-Maxwell case, supersymmetry was obtained for a single value
of the source (2) [12]. In the model we study here, there are two Wilson lines, with a
one-parameter family of values of the Wilson lines which give supersymmetric solitons.
There are also Poincar´e-AdS solutions and domain wall solutions dressed by constant
3
Wilson loops, which satisfy the same boundary conditions.
We observe that for the Poincar´e-AdS solutions regularity requires a quantization
condition on the Wilson loops which was missed in [12]. This arises from considering
the uplift of the configuration to a M4×S7solution of M theory, where the Wilson
loops parametrise a shift on the S7as we go around the ϕcircle.
For fixed flux boundary conditions, the coexistence of the soliton and the Poincar´e-
AdS and domain wall solutions leads to a degeneracy of supersymmetric solutions as
in [12]. We also consider the alternate boundary condition of fixed currents on the
boundary – we will in the sequel refer to these boundary conditions as fixed charge –
although this is actually correct only for the Euclidean continuation, as the currents
are spacelike in the Lorentzian solution. We find that, for supersymmetry-preserving
fixed charge boundary conditions, there are two distinct soliton solutions, leading to
a new kind of degeneracy of supersymmetric solutions (the Poincar´e-AdS and domain
wall solutions do not satisfy these boundary conditions, so there is no degeneracy at
fixed charge in the previous case studied in [12]).
Finally, we find that the non-supersymmetric solutions of [12] also satisfy the bound-
ary conditions which give supersymmetric solutions for fixed charge, and one branch of
those solutions has lower energy than the supersymmetric solutions. This is surprising
as we would expect the supersymmetric solutions to saturate a BPS bound, forbidding
the existence of solutions with lower energy. The BPS bound for these alternate bound-
ary conditions has however not been explicitly worked out as far as we are aware. We
discuss this result in light of the positive energy theorem [15,16], which implies that the
energy of a supersymmetry preserving solution is lower than the energy of any other
solution satisfying the same boundary conditions. We show that our result is not in
contradiction with this general property. The central point of the argument is that a
necessary condition for the positive energy theorem to apply is the existence, for the
non-supersymmetric solution, of an asymptotic Killing spinor which coincides, up to
O(1/r2) terms at radial infinity, with the Killing spinor of the supersymmetric one.
Since the latter has antiperiodic boundary conditions along the circle at infinity, in or-
der for the positive energy theorem to apply, the non-supersymmetric solutions should
admit an asymptotic Killing spinor with the same property at the boundary. As we
shall prove, this is the case only if the charges at infinity have specific values, for which
the energy of the non-supersymmetric solution exceeds that of the supersymmetric one.
In summary, there is no contradiction with the positive energy theorem if we include
among the boundary conditions those applying to the asymptotic Killing spinor.
Another important direction for future work is to find a more general understanding
of the degeneracy of the susy solutions. We believe this is a generic feature of such
boundary conditions; we intend to provide a general proof in a forthcoming paper.
It is also possible to construct black holes in this theory [1723] and endow them
with Wilson lines along the lines of [24]. This will provide an even more complete phase
4
diagram of this model that we leave to analyze in the future.
The outline of the paper is as follows. In the next Section 2, we review the model
under consideration. In Section 3, we present the soliton solutions within this model,
and explain their relation to the solutions of [12]. In Section 4, we discuss the solutions
with constant fluxes, and explain the quantisation of the flux from demanding a well-
behaved action on the S7factor in the uplift. In Section 5, we find the supersymmetric
solutions for both fixed flux and fixed charge boundary conditions. In Section 6, we
describe the phase structure for the different boundary conditions, and point out that for
supersymmetric fixed charge boundary conditions there are both supersymmetric and
non-supersymmetric solutions, with a surprising family of non-supersymmetric solutions
of lower energy and free energy than the supersymmetric ones. The consistency of this
result with the positive energy theorem for asymptotically AdS solutions is discussed in
subsection 6.3.1.
2 The model
We are interested in studying the dilatonic sector of the STU model of the SO(8)-gauged,
N= 8 supergravity with action:
S=1
2κZd4xg R
3
X
i=1
(Φi)2
2+2
L2cosh (Φi)1
4
4
X
i=1
X2
i¯
F2
i!,(3)
where ¯
Fiare two forms, related with gauge fields in the standard way
¯
Fi=d¯
Ai, Xi=e1
2~ai·~
Φ,~
Φ = (Φ1,Φ2,Φ3),(4)
and
~a1= (1,1,1) , ~a2= (1,1,1) , ~a3= (1,1,1) , ~a4= (1,1,1) .(5)
We will be interested in purely magnetic solutions, in which case it is consistent to trun-
cate the axions to zero. The Lagrangian (3) can be obtained from the compactification
of eleven dimensional supergravity over the seven sphere with the ansatz [25]
ds2
11 =˜
2/3ds2
4+ 4 L2˜
1/3
4
X
i=1
X1
i 2
i+µ2
ii+1
2L¯
Ai2!,(6)
F=1
L4
4
X
i=1 X2
iµ2
i˜
Xi+L X1
i?4dXi2
i
4L2X
i
X2
iµiii+1
2L¯
Ai?4¯
Fi,(7)
5
摘要:

SupersymmetricsolitonsingaugedN=8supergravityAndresAnabalon*1,AntonioGallerati„2,SimonRoss…3,MarioTrigiante§2,41DepartamentodeCiencias,FacultaddeArtesLiberales,UniversidadAdolfoIba~nez,AvenidaDiagonallasTorres2640,Pe~nalolen,Santiago,Chile2PolitecnicodiTorino,DipartimentodiScienzaApplicataeTecnol...

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