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ratio of the in
aton to the gravitino mass. It is interesting
to notice that from (27), we can write the supersymmetry
breaking scale in terms of the -parameter:

M5:2 104: (29)
Hence for a value of :1 we can get 1013GeV.
Lower values of the supersymmetry breaking scale can be
obtained by reducing . However, since the in
aton mass
is
m=m3=2p; (30)
we may end up with an in
aton whose mass is substantially
lighter than the gravitino. For these values of ;, we
have thati1013=M;f103=M, and the number of
efoldings is110.
5We conclude then that with moderate values of be-
tween:1:01 we can get supersymmetry breaking scales
between 10111013without major ne tunings. We eas-
ily get enough efoldings, and furthermore, the in
aton is
lighter than the gravitino by an amount given byp.
For the above range of parameters we can compare the
predicted value of nSin our model with observational con-
straints. This is shown in the right panel of Fig. 1. The
yellow region is the current cosmological constraints from
WMAP5 [11] and the other colored areas are the predic-
tions for our model with minimal ne tuning for an stable
(unstable)Xpotential, i.e. the eld is concave (convex) re-
spectively. The constraints will improve greatly when the
Planck satellite releases its results next year, and therefore
our model can be tested much more accurately.
Reheating can proceed in many ways, since we have not
provided a detailed microscopic model. Once in the non-
linear regime, the XNLeld (whose scalar component is
made of a goldstino bilinear) could eciently convert the
f2-energy density into radiation. We can calculate the
amount of entropy and particle density by using the Boltz-
man equation and assuming that the pair of Goldstinos
will have an out-of-equilibrium decay[16]. Using that
TRH= 1010p
f=GeV3=2
GeV (31)
we obtain a range 107< TRH<109. This produces a
particle abundance of n107090which are standard
values. We can also compute the amount of entropy gen-
erated by the out-of-equilibrium decay as
Sf=Si= 107(p
f=GeV )1=2(32)
which yields values in the range 10 to 1, and assures that
there is no entropy overproduction. We could also compute
the depletion of this energy through the soft couplings (10)
yielding very similar values as above. In both cases, we
can get sucient reheating with temperatures betweenpf
and a fraction of m3=2. The true value depends very much
on the details of the microscopic model. However, thereseems to be no obstruction to reheating the universe to
and acceptable value of temperature, particle abundances
and entropy. We are currently working in a more detailed
theory incorporating our scenario [25].
4. Conclusions
In this short note we have studied the possibility of hav-
ing supersymmetry breaking as the driving force of in
a-
tion. We have used the unique chiral supereld Xwhich
represents the breaking of conformal invariance in the UV,
and whose fermionic component becomes the goldstino at
low energies. Its auxiliary eld is the F-term which gets
the vacuum expectation value breaking supersymmetry.
It is crucial in our analysis to have explicit R-symmetry
breaking along with supersymmetry breaking. This allows
us to avoid the problem in supergravity and to take the
supersymmetric limit. The simplest model we obtain de-
scribes the components of Xwell below the Planck scale.
It is written in terms of three parameters: the supersym-
metry breaking parameter fand the masses of the real and
imaginary components of the eld x(the scalar component
of X). In our analysis the imaginary part of xplays the role
of the in
aton, and its mass was shown to be smaller than
the gravitino mass by an amount given byp. This imag-
inary component represents a pseudo-goldstone boson, or
rather, a pseudomoduli. In supersymmetric theories such
elds abound, and any of them could be used to construct
some form of hybrid in
ation. In our case, however, we
want to use the minimal choice that is naturally provided
by the universal supereld Xthat must exist in any su-
persymmetric theory.
Since we have not presented any detailed model, the cos-
mological consequences are a bit rudimentary, especially
concerning reheating at the end of in
ation. However, the
comparison of the simplest model with present data, yields
very interesting values for the supersymmetry breaking
scale, and the ratio of the in
aton and gravitino masses.
6Figure 1: Left panel: The potential as a function of ( ) and () components of the eld X. Note the nearly
at direction ( ) that we use for our
in

ratio of the in

aton to the gravitino mass. It is interesting

to notice that from (27), we can write the supersymmetry

breaking scale in terms of the -parameter:

M5:2 104: (29)

Hence for a value of :1 we can get 1013GeV.

Lower values of the supersymmetry breaking scale can be

obtained by reducing . However, since the in

aton mass

is

m=m3=2p; (30)

we may end up with an in

aton whose mass is substantially

lighter than the gravitino. For these values of ;, we

have thati1013=M;f103=M, and the number of

efoldings is110.

5We conclude then that with moderate values of be-

tween:1:01 we can get supersymmetry breaking scales

between 10111013without major ne tunings. We eas-

ily get enough efoldings, and furthermore, the in

aton is

lighter than the gravitino by an amount given byp.

For the above range of parameters we can compare the

predicted value of nSin our model with observational con-

straints. This is shown in the right panel of Fig. 1. The

yellow region is the current cosmological constraints from

WMAP5 [11] and the other colored areas are the predic-

tions for our model with minimal ne tuning for an stable

(unstable)Xpotential, i.e. the eld is concave (convex) re-

spectively. The constraints will improve greatly when the

Planck satellite releases its results next year, and therefore

our model can be tested much more accurately.

Reheating can proceed in many ways, since we have not

provided a detailed microscopic model. Once in the non-

linear regime, the XNLeld (whose scalar component is

made of a goldstino bilinear) could eciently convert the

f2-energy density into radiation. We can calculate the

amount of entropy and particle density by using the Boltz-

man equation and assuming that the pair of Goldstinos

will have an out-of-equilibrium decay[16]. Using that

TRH= 1010p

f=GeV3=2

GeV (31)

we obtain a range 107< TRH<109. This produces a

particle abundance of n107090which are standard

values. We can also compute the amount of entropy gen-

erated by the out-of-equilibrium decay as

Sf=Si= 107(p

f=GeV )1=2(32)

which yields values in the range 10 to 1, and assures that

there is no entropy overproduction. We could also compute

the depletion of this energy through the soft couplings (10)

yielding very similar values as above. In both cases, we

can get sucient reheating with temperatures betweenpf

and a fraction of m3=2. The true value depends very much

on the details of the microscopic model. However, thereseems to be no obstruction to reheating the universe to

and acceptable value of temperature, particle abundances

and entropy. We are currently working in a more detailed

theory incorporating our scenario [25].

4. Conclusions

In this short note we have studied the possibility of hav-

ing supersymmetry breaking as the driving force of in

a-

tion. We have used the unique chiral supereld Xwhich

represents the breaking of conformal invariance in the UV,

and whose fermionic component becomes the goldstino at

low energies. Its auxiliary eld is the F-term which gets

the vacuum expectation value breaking supersymmetry.

It is crucial in our analysis to have explicit R-symmetry

breaking along with supersymmetry breaking. This allows

us to avoid the problem in supergravity and to take the

supersymmetric limit. The simplest model we obtain de-

scribes the components of Xwell below the Planck scale.

It is written in terms of three parameters: the supersym-

metry breaking parameter fand the masses of the real and

imaginary components of the eld x(the scalar component

of X). In our analysis the imaginary part of xplays the role

of the in

aton, and its mass was shown to be smaller than

the gravitino mass by an amount given byp. This imag-

inary component represents a pseudo-goldstone boson, or

rather, a pseudomoduli. In supersymmetric theories such

elds abound, and any of them could be used to construct

some form of hybrid in

ation. In our case, however, we

want to use the minimal choice that is naturally provided

by the universal supereld Xthat must exist in any su-

persymmetric theory.

Since we have not presented any detailed model, the cos-

mological consequences are a bit rudimentary, especially

concerning reheating at the end of in

ation. However, the

comparison of the simplest model with present data, yields

very interesting values for the supersymmetry breaking

scale, and the ratio of the in

aton and gravitino masses.

6Figure 1: Left panel: The potential as a function of ( ) and () components of the eld X. Note the nearly

at direction ( ) that we use for our

in