153 research outputs found
Seven-Disk Manifold, alpha-attractors and B-modes
Cosmological alpha-attractor models in \cN=1 supergravity are based on
hyperbolic geometry of a Poincar\'e disk with the radius square {\cal
R}^2=3\alpha. The predictions for the B-modes, r\approx 3\alpha {4\over N^2},
depend on moduli space geometry and are robust for a rather general class of
potentials. Here we notice that starting with M-theory compactified on a
7-manifold with G_2 holonomy, with a special choice of Betti numbers, one can
obtain d=4 \cN=1 supergravity with rank 7 scalar coset \Big[{SL(2)\over
SO(2)}\Big]^7. In a model where these 7 unit size Poincar\'e disks have
identified moduli one finds that 3 alpha =7. Assuming that the moduli space
geometry of the phenomenological models is inherited from this version of
M-theory, one would predict r \approx 10^{-2} for 53 e-foldings. We also
describe the related maximal supergravity and M/string theory models leading to
preferred values 3 alpha =1,2,3,4,5,6,7.Comment: 11 p, 1 figur
Degeneration of Groups of Type E7 and Minimal Coupling in Supergravity
We study properties of D = 4, N >1 extended supergravities (and related
compactifications of superstring theory) and their consistent truncation to the
phenomenologically interesting models of N = 1 supergravity. This involves a
detailed classification of the "degenerations" of the duality groups of type
E7, when the corresponding quartic invariant polynomial built from the
symplectic irreducible representation of G4 "degenerates" into a perfect
square. With regard to cosmological applications, we conclude that the
consistent truncation to N = 1 from higher-dimensional or higher-N theory gives
a zero measure minimal coupling of vectors. A non-minimal coupling involving
vectors coupled to scalars and axions is generic. These features of
supergravity, following from the electric-magnetic duality, may be useful in
other applications, like stabilization of moduli, and in studies of
non-perturbative black-hole solutions of supergravity/string theory.Comment: 1+40 pages, 5 Tables; v2 : 1+41 pages, Sec. 3 extended, Sec. 3.1
replaced, Sec. 4.3 removed, one Ref. added, other minor change
Cosmology with orthogonal nilpotent superfields
We study the application of a supersymmetric model with two constrained
supermultiplets to inflationary cosmology. The first superfield S is a
stabilizer chiral superfield satisfying a nilpotency condition of degree 2,
S^2=0. The second superfield Phi is the inflaton chiral superfield, which can
be combined into a real superfield B=(Phi-Phi*)/2i. The real superfield B is
orthogonal to S, S B=0, and satisfies a nilpotency condition of degree 3,
B^3=0. We show that these constraints remove from the spectrum the complex
scalar sgoldstino, the real scalar inflaton partner (i.e. the "sinflaton"), and
the fermionic inflatino. The corresponding supergravity model with de Sitter
vacua describes a graviton, a massive gravitino, and one real scalar inflaton,
with both the goldstino and inflatino being absent in unitary gauge. We also
discuss relaxed superfield constraints where S^2=0 and S Phi* is chiral, which
removes the sgoldstino and inflatino, but leaves the sinflaton in the spectrum.
The cosmological model building in both of these inflatino-less models offers
some advantages over existing constructions.Comment: 20+9 pages; v2: version to appear in PR
Minimal Supergravity Models of Inflation
We present a superconformal master action for a class of supergravity models
with one arbitrary function defining the Jordan frame. It leads to a
gauge-invariant action for a real vector multiplet, which upon gauge fixing
describes a massive vector multiplet, or to a dual formulation with a linear
multiplet and a massive tensor field. In both cases the models have one real
scalar, the inflaton, naturally suited for single-field inflation. Vectors and
tensors required by supersymmetry to complement a single real scalar do not
acquire vev's during inflation, so there is no need to stabilize the extra
scalars which are always present in the theories with chiral matter multiplets.
The new class of models can describe any inflaton potential which vanishes at
its minimum and grows monotonically away from the minimum. In this class of
supergravity models one can fit any desirable choice of inflationary parameters
n_s and r.Comment: 25 pages, 5 figures, the version to appear in Phys. Rev.
Higher Order Corrections in Minimal Supergravity Models of Inflation
We study higher order corrections in new minimal supergravity models of a
single scalar field inflation. The gauging in these models leads to a massive
vector multiplet and the D-term potential for the inflaton field with a
coupling g^{2} ~ 10^{-10}. In the de-Higgsed phase with vanishing g^2, the
chiral and vector multiplets are non-interacting, and the potential vanishes.
We present generic manifestly supersymmetric higher order corrections for these
models. In particular, for a supersymmetric gravity model -R+ R^2 we derive
manifestly supersymmetric corrections corresponding to R^n. The dual version
corresponds to a standard supergravity model with a single scalar and a massive
vector. It includes, in addition, higher Maxwell curvature/scalar interaction
terms of the Born-Infeld type and a modified D-term scalar field potential. We
use the dual version of the model to argue that higher order corrections do not
affect the last 60 e-foldings of inflation; for example the \xi R^4 correction
is irrelevant as long as \xi< 10^{24}.Comment: 25 pages, the version to appear in JCA
Linear Versus Non-linear Supersymmetry, in General
We study superconformal and supergravity models with constrained superfields.
The underlying version of such models with all unconstrained superfields and
linearly realized supersymmetry is presented here, in addition to the physical
multiplets there are Lagrange multiplier (LM) superfields. Once the equations
of motion for the LM superfields are solved, some of the physical superfields
become constrained. The linear supersymmetry of the original models becomes
non-linearly realized, its exact form can be deduced from the original linear
supersymmetry. Known examples of constrained superfields are shown to require
the following LM's: chiral superfields, linear superfields, general complex
superfields, some of them are multiplets with a spin.Comment: 24
Superconformal Symmetry, NMSSM, and Inflation
We identify a particularly simple class of supergravity models describing
superconformal coupling of matter to supergravity. In these models, which we
call the canonical superconformal supergravity (CSS) models, the kinetic terms
in the Jordan frame are canonical, and the scalar potential is the same as in
the global theory. The pure supergravity part of the total action has a local
Poincare supersymmetry, whereas the chiral and vector multiplets coupled to
supergravity have a larger local superconformal symmetry. The scale-free
globally supersymmetric theories, such as the NMSSM with a scale-invariant
superpotential, can be naturally embedded into this class of theories. After
the supergravity embedding, the Jordan frame scalar potential of such theories
remains scale free; it is quartic, it contains no mass terms, no
nonrenormalizable terms, no cosmological constant. The local superconformal
symmetry can be broken by additional terms, which, in the small field limit,
are suppressed by the gravitational coupling. This can be achieved by
introducing the nonminimal scalar-curvature coupling, and by taking into
account interactions with a hidden sector. In this approach, the smallness of
the mass parameters in the NMSSM may be traced back to the original
superconformal invariance. This allows to address the \mu-problem and the
cosmological domain wall problem in this model, and to implement chaotic
inflation in the NMSSM. We discuss the gravitino problem in the NMSSM
inflation, as well as the possibility to obtain a broad class of new versions
of chaotic inflation in supergravity.Comment: 55 pages, 3 figures. v2 : A discussion of the gravitino problem in
the NMSSM inflation scenario is added; v3 : A discussion of the unitarity
bound and of the phenomenological consequences of our model is extended. An
investigation of stability with respect to the charged Higgs fields is added.
This version is more updated than published on
On N=8 attractors
We derive and solve the black hole attractor conditions of N=8 supergravity
by finding the critical points of the corresponding black hole potential. This
is achieved by a simple generalization of the symplectic structure of the
special geometry to all extended supergravities with .
There are two solutions for regular black holes, one for 1/8 BPS ones and one
for the non-BPS. We discuss the solutions of the moduli at the horizon for BPS
attractors using N=2 language. An interpretation of some of these results in
N=2 STU black hole context helps to clarify the general features of the black
hole attractors.Comment: 15 page
Perturbative and Non-perturbative N =8 Supergravity
We study extremal black holes, their ADM mass and area of the horizon in N =
8 supergravity. Contrary to intuition gained from N = 2, 4 theories, in N = 8
supergravity BPS states may become massless only at the boundary of moduli
space. We show that stringy states described in [1], which have no mass gap and
survive in the toroidal compactification in addition to massless states of
perturbative N = 8 supergravity, display a null singularity in four-dimensional
space-time, when viewed as solutions of N = 8 Einstein equations. We analyze
known methods of resolving such singularities and explain why they do not work
in D=4, N = 8 supergravity. We discuss possible implications for the issue of
UV finiteness of the four-dimensional N = 8 perturbation theory.Comment: 5p, few corrections and improvements, references added, published in
Physics Letter
Observations on Arithmetic Invariants and U-Duality Orbits in N =8 Supergravity
We establish a relation between time-like, light-like and space-like orbits of the non-compact E{7(7)}(R)symmetry and discrete E{7(7)}(Z) invariants. We discuss the U-duality invariant formula for the degeneracy of states d(Q) which in the approximation of large occupation numbers reproduces the Bekenstein-Hawking entropy formula for regular black holes with AdS_2 horizon. We explain why the states belonging to light-like orbits, corresponding to classical solutions of "light black holes with null singularity", decouple from the corresponding index. We also present a separate U-duality invariant formula for the class of light-like orbits specified by discrete E{7(7)}(Z) invariants. We conclude that the present study of the non-perturbative sector of the theory does not reveal any contradiction with the conjectured all-loop perturbative finiteness of D=4 N=8 supergravity
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