Natural inflation driven by Pseudo-Nambu-Goldstone bosons have a problem that the nearly scale invariant spectrum of density perturbations is attained only when the symmetry breaking scale is of the order of Planck scale. We show here that if one couples the PNGB to a thermal bath as in warm inflation models, the amplitude and spectral index which agrees with the WMAP data is obtained with the symmetry breaking in the GUT scale. We give a GUT model of PNGB arising out of spontaneously broken lepton number at the GUT scale which gives rise to heavy Majorana masses for the right handed neutrinos which is needed in see-saw models. This model also generates a lepton asymmetry because of the derivative coupling of the PNGB to the lepton current. A characteristic feature of this model is the prediction of large non-gaussianity which may be observed in the forthcoming PLANCK experiment.
We employ Coleman-Weinberg and Higgs potentials to implement inflation in non-supersymmetric grand unified theories (GUTs) such as SU(5) and SO(10). To realize a scalar spectral index close to 0.96, as indicated by the most recent WMAP 5-year anlaysis, the energy scale of observable inflation turns out to be of order $10^{16}$ GeV. This implies a GUT symmetry breaking scale of similar magnitude, and proton lifetime of order $10^{34}$-$10^{38}$ years. In some SO(10) models with axion dark matter, the scalar leptoquark boson exchange leads to proton decay with a lifetime of order $10^{34}$-$10^{…
We discuss the smooth hybrid inflation scenario in the context of a simple supersymmetric SO(10) GUT in 5D orbifold. In this GUT model, the SO(10) gauge symmetry is broken down to the Pati-Salam (PS) gauge group, SU(4)$_c \times$ SU(2)$_L \times$ SU(2)$_R$, by orbifold boundary conditions and all matter and Higgs multiplets are placed only on the brane (PS brane) where only the PS symmetry is manifest. Further breaking of the Pati-Salam group to the Standard Model one is realized by VEVs of the Higgs multiplets $({\bf 4},{\bf 1},{\bf 2}) \oplus (\overline{\bf 4},{\bf 1},{\bf 2})$. The gauge co…
Leptogenesis scenarios in supersymmetric hybrid inflation models are considered. Sufficient lepton asymmetry leading to successful baryogenesis can be obtained if the reheat temperature T_r>10^6 GeV and the superpotential coupling parameter kappa is in the range 10^-6<kappa<10^-2. For this range of kappa the scalar spectral index n_s=0.99+-0.01. Constraints from neutrino mixing further restrict the range of kappa that is allowed. We analyze in detail the case where the inflaton predominantly decays into the next-to-lightest right handed Majorana neutrino taking into account especially the cons…
In the present work we study GUT Coleman-Weinberg inflation with a nonminimal coupling to gravity. In this kind of model one usually finds that either the nonminimal coupling is large or the inflaton self-coupling in unnaturally small. We have shown here that the model is in agreement with the recent results from Planck for natural values of the couplings.
Sources of magnetic fields from grand unified theories are studied in the warm inflation regime. A ferromagnetic Savvidy vacuum scenario is presented that yields observationally interesting large scale magnetic fields. As an intermediate step, a general analysis is made of defect production at the onset of warm inflation and monopole constraints are obtained. Many features of this Savvidy vacuum scenario are applicable within a supercooled inflation regime and these points are discussed.
At the end of inflation the universe is frozen in a near zero-entropy state with energy density in a coherent scalar field and must be ``defrosted'' to produce the observed entropy and baryon number. We propose that the baryon asymmetry is generated by the decay of supermassive Grand Unified Theory (GUT) bosons produced non-thermally in a preheating phase after inflation. We show that baryogenesis is possible for an inflaton masses of order 10^{13} GeV and a GUT Higgs boson mass of order 10^{14} GeV, thus solving many drawbacks facing GUT baryogenesis in the old reheating scenario.
We study the Higgs inflation model realized in the supersymmetric SU(5) grand unified theory (GUT), focusing on its multifield dynamics and prediction of cosmological observables. The requirement for GUT symmetry breaking during inflation imposes tight constraints on the model parameters. We find, nevertheless, with an appropriately chosen noncanonical Kahler potential the model is in excellent agreement with the present cosmological observation. The effects from multifield dynamics is found to be minor and thus, unlike other similar supersymmetric implementation of nonminimally coupled Higgs …
In this paper, we embed the model of flipped GUT sneutrino inflation -in a flipped SU(5) or SO(10) set up- developed by Ellis et al. in a supergravity framework. The GUT symmetry is broken by a waterfall which could happen at early or late stage of the inflationary period. The full field dynamics is thus studied in detail and these two main inflationary configurations are exposed, whose cosmological predictions are both in agreement with recent astrophysical measurements. The model has an interesting feature where the inflaton has natural decay channels to the MSSM particles allowed by the GUT…
A supersymmetric hybrid inflation framework is employed to realize a class of non-minimal inflation models with $U(1)_R \times Z_n$ global symmetry. This framework naturally incorporates models based on grand unified theories by avoiding the most commonly faced monopole problem. The predictions of inflationary observables, the scalar spectral index $n_s = 0.960-0.966$ and the tensor to scalar ratio $r=0.0031-0.0045$, are in perfect agreement with the Planck 2018 data. For sub-Planckian values of the field the $Z_n$ symmetry is only allowed for $n\leq 4$.
The Standard Model Higgs boson with large nonminimal coupling to the gravitational curvature can drive cosmological inflation. We study this type of inflationary scenario in the context of supersymmetric grand unification and point out that it is naturally implemented in the {\em minimal} supersymmetric SU(5) model, and hence virtually in any GUT models. It is shown that with an appropriate Kähler potential the inflaton trajectory settles down to the Standard Model vacuum at the end of the slow roll. The predicted cosmological parameters are also consistent with the 7-year WMAP data.
We study cosmic string formation within supersymmetric grand unified theories. We consider gauge groups having a rank between 4 and 8. We examine all possible spontaneous symmetry breaking patterns from the GUT down to the standard model gauge group. Assuming standard hybrid inflation, we select all the models which can solve the GUT monopole problem, lead to baryogenesis after inflation and are consistent with proton lifetime measurements. We conclude that in all acceptable spontaneous symmetry breaking schemes, cosmic string formation is unavoidable. The strings which form at the end of infl…
Higgs inflation is attractive because it identifies the inflaton with the electroweak Higgs boson. In this work, we construct a new class of supersymmetric Higgs inflationary models in the no-scale supergravity with an SU(5) GUT group. Extending the no-scale Kahler potential and SU(5) GUT superpotential, we derive a generic potential for Higgs inflation that includes the quadratic monomial potential and a Starobinsky-type potential as special limits. This type of models can accommodate a wide range of the tensor-to-scalar ratio $r = O(10^{-3}-10^{-1})$, as well as a scalar spectral index $n_s …
A sizeable tensor-to-scalar ratio, such as recently claimed by BICEP2, would imply a scale of inflation at the typical scale of supersymmetric grand unification. This could be an accident, or strong support for supersymmetric theories. Models of F-term hybrid inflation naturally connect the GUT scale with the inflationary scale, but they also predict the tensor-to-scalar ratio to be unmeasurably small. In this work we analyze a general UV embedding of F-term hybrid inflation into a supergravity theory with a general Kahler potential. The CMB observables are generated during the early phase of …
We consider a scenario of cosmological inflation coming from a grand unified theory in higher dimensional orbifold. Flatness of the potential is automatically guaranteed in this orbifold setup thanks to the nonlocality of the Wilson line on higher dimensions and the local quantum gravitational corrections are exponentially suppressed. The spectral index of scalar perturbation (n_s =0.92 - 0.97) and a significant production of gravitational waves are predicted (r= T/S= 0.01 - 0.12) in the perturbative regime of gauge interaction, (1/g_4 = (5-20) X 2 pi R Mpl) where the size of compactification …
We discuss a five dimensional inflationary scenario based on a supersymmetric SO(10) model compactified on $S^1/(Z_2\times Z_2')$. Inflation is implemented through scalar potentials on four dimensional branes, and a brane-localized Einstein-Hilbert term is essential to make both brane vacuum energies positive during inflation. The orbifold boundary conditions break the SO(10) gauge symmetry to $SU(4)_c\times SU(2)_L\times SU(2)_R$ ($\equiv H$). The inflationary scenario yields $δT/T\propto (M/M_{\rm Planck})^2$, which fixes $M$, the symmetry breaking scale of $H$ to be close to the SUSY GUT sc…
The surprisingly large value of $r$, the ratio of power in tensor to scalar density perturbations in the CMB reported by the BICEP2 Collaboration, if confirmed, provides strong evidence for Inflation at the GUT scale. While the Inflationary signal remains the best motivated source, a large value of $r$ alone would still allow for the possibility that a comparable gravitational wave background might result from a self ordering scalar field (SOSF) transition that takes place later at somewhat lower energy. We find that even without detailed considerations of the predicted BICEP signature of such…
We consider non-supersymmetric GUT inflation models in which intermediate mass monopoles may survive inflation because of the restricted number of e-foldings experienced by the accompanying symmetry breaking. Thus, an observable flux of primordial magnetic monopoles, comparable to or a few orders below the Parker limit, may be present in the galaxy. The mass scale associated with the intermediate symmetry breaking is $10^{13}$ GeV for an observable flux level, with the corresponding monopoles an order of magnitude or so heavier. Examples based on $SO(10)$ and $E_6$ yield such intermediate mass…
We have investigated a number of GUT models for the possibility that their Higgs fields might be responsible for inflation in the early universe. In addition to models having an intrinsic Planck mass parameter, we have entertained classically scale invariant models in which the Planck scale itself as well as the GUT scale is induced by spontaneous gauge symmetry breaking. We found that in a non-supersymmetric SU(5) with the usual adjoint Higgs, but with large non-minimal coupling to the curvature, there are flat directions that might lead to inflation. Interestingly, the one of lowest energy b…
We investigate the possibility of a bosonic preheating in the simplest model of supersymmetric Hybridinflation (F-term inflation), which was considered first by Dvali et al. Here the inflationary superpotential is of the O'Raifertaigh-Witten type. The end of inflation is related to a non-thermal phase transition, which in the context of left-right symmetric models lowers the rank of the gauge group. Using the homogeneous classical field ansatz for the appearing condensates, our results indicate that the parametric creation of bosonic particles does not occure in the model under consideration.
In the context of hybrid inflation at the scale of grand unification, it is shown that, if (some of) the gauge bosons of the unbroken grand unified group obtain a flat superhorizon spectrum of perturbations from inflation they can affect or even generate both the observed curvature perturbation and simultaneously produce a sizable primordial magnetic field capable of explaining galactic magnetism. The mechanism employs the vector curvaton idea for a supermassive grand unified gauge boson after the breaking of grand unification.
We discuss two important modifications of inflationary paradigm. Until very recently we believed that inflation automatically leads to flatness of the universe, Omega = 1. We also thought that post-inflationary phase transitions in GUTs may occur only after thermalization, which made it very difficult to have baryogenesis in GUTs and to obtain superheavy topological defects after inflation. We will describe a very simple version of chaotic inflation which leads to a division of the universe into infinitely many open universes with all possible values of Omega from 1 to 0. We will show also tha…
At the end of inflation the Universe is frozen in a near zero-entropy state with energy density in a coherent scalar field and must be "defrosted" to produce the observed entropy and baryon number. Baryon asymmetry may be generated by the decay of supermassive Grand Unified Theory (GUT) bosons produced non-thermally in a preheating phase after inflation, thus solving many drawbacks facing GUT baryogenesis in the old reheating scenario.
We analyse the prospects for constructing hybrid models of inflation that provide a dynamical realisation of the apparent closeness between the supersymmetric GUT scale and the possible scale of cosmological inflation. In the first place, we consider models based on the flipped SU(5)$\times$U(1) gauge group, which has no magnetic monopoles. In one model, the inflaton is identified with a sneutrino field, and in the other model it is a gauge singlet. In both cases we find regions of the model parameter spaces that are compatible with the experimental magnitudes of the scalar perturbations, $A_s…
We show that Supersymmetric models with Type I seesaw neutrino masses support slow roll inflection point inflation. The inflaton is the D-flat direction labelled by the chiral invariant HLN composed of the Higgs(H), slepton(L) and conjugate sneutrino(N) superfields. The scale of inflation and fine tuning is set by the conjugate neutrino Majorana mass $M_{ν^c} \sim 10^6-10^{12}$ GeV. The cubic term in the (quartic) inflaton potential is dominantly from superpotential (not soft Susy breaking) couplings. The tuning conditions are thus insensitive to soft supersymmetry breaking parameters and are …
Models of induced-gravity inflation are formulated within Supergravity employing as inflaton the Higgs field which leads to a spontaneous breaking of a U(1)B-L symmetry at Mgut=2x10^16 GeV. We use a renormalizable superpotential, fixed by a U(1) R symmetry, and Kahler potentials which exhibit a quadratic non-minimal coupling to gravity with or without an independent kinetic mixing in the inflaton sector. In both cases we find inflationary solutions of Starobinsky type whereas in the latter case, others (more marginal) which resemble those of linear inflation arise too. In all cases the inflato…
Currently favoured extensions of the Standard Model typically contain `flaton fields' defined as fields with large vacuum expectation values (vevs) and almost flat potentials. If a flaton field is trapped at the origin in the early universe, one expects `thermal inflation' to take place before it rolls away to the true vacuum, because the finite-temperature correction to the potential will hold it at the origin until the temperature falls below $1\TeV$ or so. In the first part of the paper, that expectation is confirmed by an estimate of the finite temperature corrections and of the tunneling …
A two-components mixture fluid which complies with the gamma law is considered in the framework of inflation with finite temperature. The model is developed for a quartic scalar potential without symmetry breaking. The radiation energy density is assumed to be zero when inflation starts and remains below the GUT temperature during the inflationary stage. Furthermore, provides the necessary number of e-folds and sufficient radiation energy density to GUT baryogenesis can take place near the minimum energetic configuration.
It is shown that, in supergravity models of inflation where the gauge kinetic function of a gauge field is modulated by the inflaton, we can obtain a new inflationary attractor solution, in which the roll-over of the inflaton suffers additional impedance due to the vector field backreaction. As a result, directions of the scalar potential which, due to strong Kaehler corrections, become too steep and curved to normally support slow-roll inflation can now naturally do so. This solves the infamous eta-problem of inflation in supergravity and also keeps the spectral index of the curvature perturb…
We apply the idea of spiral inflation to Coleman-Weinberg potential, and show that inflation matching well observations is allowed for a symmetry-breaking scale ranging from an intermediate scale to GUT scale even if the quartic coupling $λ$ is of $\mathcal{O}(0.1)$. The tensor-to-scalar ratio can be of $\mathcal{O}(0.01)$ in case of GUT scale symmetry-breaking.
The supersymmetric model of hybrid inflation is interesting not only because of its naturalness but also because of another reason. Its energy scale determined by the COBE normalization is 10^15 - 10^16 GeV. It happens to be the energy scale of interest in particle physics, namely, the mass scale of right-handed neutrinos or the energy scale of the gauge-coupling unification. It is true that topological defects are produced after the hybrid inflation if it is related to a U(1)_B-L or a GUT-symmetry breaking, and hence one cannot naively identify models of particle physics with that of inflatio…
We study the feasibility of realizing supersymmetric new inflation model, introduced by Senoguz and Shafi in [1], for $SU(5)$ and flipped $SU(5)$ models of grand unified theories (GUTs). This realization requires an additional $U(1)_R \times Z_{n}$ symmetry for its successful implementation. The standard model (SM) gauge singlet scalar components of $24_H$ and $10_H$ GUT Higgs superfields are respectively employed to realize successful inflation in $SU(5)$ and flipped $SU(5)$ models. The predictions of the various inflationary observables lie within the recent Planck bounds on the scalar spect…
In this talk, I shall focus on theories beyond the Standard Model which predict massive neutrinos. Hybrid inflation emerges naturally in these theories: the slow-rolling inflaton field is a gauge singlet which couples with a GUT Higgs field which triggers the end of inflation. In the standard scenario, spontaneous symmetry breaking takes place at the end of inflation at a scale $M$; $M_{GUT} > M > M_Z$ for inflation to solve the GUT monopole problem and cosmic strings always form at this intermediate scale. WMAP data constrain $M \in [10^{14.5}-10^{15.5}]$ GeV and the singlet-Higgs coupling $κ…
In this paper we provide a no-scale supergravity scenario of hybrid inflation with R-symmetry being broken maximally. We investigate the inflation dynamics in details in both cases of pure F-term hybrid inflation and when adding constant Fayet-Iliopoulos D-terms. The effective inflation potential is asymptotically flat in a region of the parameter space in both cases. We explore all regions in the parameter space when discussing the constraints from the observables. We point out a connection between inflation, R-symmetry breaking and GUT scales. The moduli backreaction and SUSY breaking effect…
Spontaneous breaking of conformal symmetry has been widely exploited in successful model building of both inflationary cosmology and particle physics phenomenology. Conformal Grand Unified Theory (CGUT) inflation provides the same scalar tilt and tensor-to-scalar ratio as of Starobinsky and Higgs inflation. Moreover, it predicts a proton life time compatible with the current experimental bound. In this paper, we extend CGUT to account for the production of dark matter and the reheating of the Standard Model. To this end, we introduce a hidden sector directly coupled to the inflaton, whereas th…
We explore the upper bound on the tensor-to-scalar ratio $r$ in supersymmetric (F-term) hybrid inflation models with the gauge symmetry breaking scale set equal to the value $2.86\cdot10^{16} {\rm GeV}$, as dictated by the unification of the MSSM gauge couplings. We employ a unique renormalizable superpotential and a quasi-canonical Kähler potential, and the scalar spectral index $n_s$ is required to lie within the two-sigma interval from the central value found by the Planck satellite. In a sizable region of the parameter space the potential along the inflationary trajectory is a monotonicall…
In this paper, we generalize Coleman-Weinberg (CW) inflation in grand unified theories (GUTs) such as $\text{SU}(5)$ and $\text{SO}(10)$ by means of considering two complex singlet fields with conformal invariance. In this framework, inflation emerges from a spontaneously broken conformal symmetry. The GUT symmetry implies a potential with a CW form, as a consequence of radiative corrections. The conformal symmetry flattens the above VEV branch of the CW potential to a Starobinsky plateau. As a result, we obtain $n_{s}\sim 1-\frac{2}{N}$ and $r\sim \frac{12}{N^2}$ for $N\sim 50-60$ e-foldings.…
This is a short review of string cosmology. We wish to connect string-scale physics as closely as possible to observables accessible to current or near-future experiments. Our possible best hope to do so is a description of inflation in string theory. The energy scale of inflation can be as high as that of Grand Unification (GUT). If this is the case, this is the closest we can possibly get in energy scales to string-scale physics. Hence, GUT-scale inflation may be our best candidate phenomenon to preserve traces of string-scale dynamics. Our chance to look for such traces is the primordial gr…
We propose an entirely new class of particle physics models of inflation based on the phase transition associated with the spontaneous breaking of family symmetry responsible for the generation of the effective quark and lepton Yukawa couplings. We show that the Higgs fields responsible for the breaking of family symmetry, called flavons, are natural candidates for the inflaton field in new inflation, or the waterfall fields in hybrid inflation. This opens up a rich vein of possibilities for inflation, all linked to the physics of flavour, with interesting cosmological and phenomenological imp…
A realistic tribrid model of sneutrino inflation is constructed in an $R$-symmetric $SU(5)$ grand unified theory (GUT). To avoid the monopole problem, a pseudosmooth inflationary trajectory is generated with the help of an additional $Z_5$ symmetry which is broken during and after inflation. The predictions of inflationary parameters are made at the central value of the scalar spectral index, $n_s =0.968$. The largest possible value of the tensor to scalar ratio, $r\lesssim 0.0027$, is obtained with sub-Planckian field values ($\lesssim m_P$). A successful realization of reheating and leptogen…
We describe how quartic ($λϕ^4$) inflation with non-minimal coupling to gravity is realized in realistic supersymmetric $SO(10)$ models. In a well-motivated example the $16-\overline{16}$ Higgs multiplets, which break $SO(10)$ to $SU(5)$ and yield masses for the right-handed neutrinos, provide the inflaton field $ϕ$. Thus, leptogenesis is a natural outcome in this class of $SO(10)$ models. Moreover, the adjoint (45-plet) Higgs also acquires a GUT scale value during inflation so that the monopole problem is evaded. The scalar spectral index $n_s$ is in good agreement with the observations and $…
We show that the parameter space for F-term inflation which predict the formation of cosmic strings is larger than previously estimated. Firstly, because realistic embeddings in GUT theories alter the standard scenerio, making the inflationary potential less steep. Secondly, the strings which form at the end of inflation are not necessarily topologically stable down to low scales. In shifted and smooth inflation strings do not form at all. We also discuss D-term inflation; here the possibilities are much more limited to enlargen paramer space.
We show that spontaneous breaking of global $B-L$ symmetry responsible for small neutrino masses via the seesaw mechanism provides a unified picture of hybrid inflation and dark matter if the scale of $B-L$ breaking is close to the GUT scale. The majoron which acquires a small mass in the milli-eV range due to Planck scale breaking of $B-L$ is the dark matter candidate. The coupling of the majoron field to the neutrino induces a small violation of CPT and Lorentz invariance at the present epoch. We discuss some of the phenomenological and cosmological implications of the model.
The most natural way to break the GUT gauge symmetry is with a Higgs field whose vacuum expectation value is of order $10^{16}\,\mbox{GeV}$ but whose mass is of order $10^2$ to $10^3\,\mbox{GeV}$. This can lead to a cosmological history radically different from what is usually assumed to have occurred between the standard inflationary and nucleosynthesis epochs, which may solve the gravitino and Polonyi/moduli problems in a natural way.
Cosmological Collider Physics gives us the opportunity to probe high-energy physics from observing the spacetime fluctuations generated during inflation imprinted on the cosmic microwave background. In other words, it is a method to investigate physics on energy scales that cannot be reached by terrestrial accelerators by means of precise observations of the universe. In this paper, we focus on the case where the GUT scale is close to the energy scale of inflation, and calculate three point function of inflaton by exchanging the Higgs boson in GUT at tree level. The results are found to be con…
If the recent measurement of B-mode polarization by BICEP2 is due to primordial gravitational waves, it implies that inflation was driven by energy densities at the GUT scale $M_{GUT} \sim 2\times 10^{16} GeV$. This favors single-field chaotic inflation models. These models require transplanckian excursions of the inflaton, forcing one to address the UV completion of the theory. We use a benchmark 4d effective field theory of axion-4-form inflation to argue that inflation driven by a quadratic potential (with small corrections) is well motivated in the context of high-scale string theory model…
During inflation primordial quantum fluctuations of the spacetime metric become classical and there is a spontaneous CPT violation by the spin connection coupling terms of the metric with fermions. The energy levels of the left and the right chirality neutrinos is split which gives rise to a net lepton asymmetry at equilibrium. A net baryon asymmetry of the same magnitude can be generated from this lepton asymmetry either by a GUT, $B-L$ symmetry or by electroweak sphaleron processes which preserve $B+L$ symmetry. If the amplitude of the primordial tensor perturbations is of the order of $10^{…
We realize smooth hybrid inflation in the framework of supersymmetric $SU(5) \times U(1)_χ\subset SO(10)$ model which provides a natural solution to the monopole problem appearing in the spontaneous symmetry breaking of $SU(5)$. The breaking of $U(1)_χ$ symmetry leaves a residual discrete $Z_2$ symmetry, that serves as the MSSM matter parity, realizing the possibility of the lightest supersymmetric particle as a cold dark matter candidate. The $d = 5$ proton lifetime for the decay $p \rightarrow K^+ \barν$, mediated by color-triplet Higgsinos is found to satisfy current experimental bounds if …
No-scale supergravity and the flipped SU(5)$\times$U(1) gauge group provide an ambitious prototype string-inspired scenario for physics below the string scale, which can accommodate the Starobinsky-like inflation favoured by observation when the inflaton is associated with one of the singlet fields associated with neutrino mass generation. During inflation, the vacuum remains in the unbroken GUT phase, and GUT symmetry breaking occurs later when a field with a flat direction (the flaton) acquires a vacuum expectation value. Inflaton decay and the reheating process depend crucially on GUT symme…
We consider the basic supersymmetric (SUSY) models of F-term hybrid inflation (FHI). We show that a simple class of Kaehler potentials ensures a resolution to the ηproblem and allows for inflation of hilltop type. As a consequence, observationally acceptable values for the spectral index, ns, can be achieved constraining the coefficient c4k of the quartic supergravity correction to the inflationary potential. For about the central value of ns, in the case of standard FHI, the grand unification (GUT) scale turns out to be well below its SUSY value with the relevant coupling constant κin the ran…
We study the realistic structure of F-term Nambu-Goto cosmic strings forming in a general supersymmetric Grand Unified Theory implementation, assuming standard hybrid inflation. Examining the symmetry breaking of the unification gauge group down to the Standard Model, we discuss the minimal field content necessary to describe abelian cosmic strings appearing at the end of inflation. We find that several fields will condense in most theories, questioning the plausible occurrence of associated currents (bosonic and fermionic). We perturbatively evaluate the modification of their energy per unit …
In this paper, we consider high scale (100 TeV) supersymmetry (SUSY) breaking and realize the idea of hilltop supernatural inflation in concrete particle physics models based on flipped-SU(5) and Pati-Salam models in the framework of supersymmetric grand unified theories (SUSY GUTs). The inflaton can be a flat direction including right-handed sneutrino and the waterfall field is a GUT Higgs. The spectral index is $n_s=0.96$ which fits very well with recent data by PLANCK satellite. There is no both thermal and non-thermal gravitino problems. Non-thermal leptogenesis can be resulted from the de…
Inflation arises in supersymmetric grand unified theories (susy GUTs) without fine tuning and cosmic strings usually form at the end of inflation. Hence both strings and inflation contribute to the density perturbations in the very early universe which lead to structure formation and to CMB anisotropies. This may give us a hint as to the $B-L$ breaking scale.
