arXiv subjects

Ila Garg

Publications and source records attributed to Ila Garg.

8 recordsLinked to original sources

arXiv2018

NMSGUT emergence and Trans-Unification RG flows

Consistency of trans-unification RG evolution is used to discuss the domain of definition of the New Minimal Supersymmetric SO(10) GUT (NMSGUT). We compute the 1-loop RGE $β$ functions, simplifying generic formulae using constraints of gauge invariance and superpotential structure. We also calculate the 2 loop contributions to the gauge coupling and gaugino mass and indicate how to get full 2 loop results for all couplings. Our method overcomes combinatorial barriers that frustrate computer algebra based attempts to calculate SO(10) $β$ functions involving large irreps. Use of the RGEs identifies a perturbative domain $Q < M_E$, where $M_E <M_{Planck}$ is the \emph{scale of emergence} where the NMSGUT, with GUT compatible soft supersymmetry breaking terms emerges from the strong UV dynamics associated with the Landau poles in gauge and Yukawa couplings. Due to the strength of the RG flows the Landau poles for gauge and Yukawa couplings lie near a cutoff scale $Λ_E $ for the perturbative dynamics of the NMSGUT which just above $M_E$. SO(10) RG flows into the IR are shown to facilitate small gaugino masses and generation of negative Non Universal Higgs masses squared needed by realistic NMSGUT fits of low energy data. Running the simple canonical theory emergent at $M_E$ through $M_X$ down to the electroweak scale enables tests of candidate scenarios such as supergravity based NMSGUT with canonical kinetic terms and NMSGUT based dynamical Yukawa unification.

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arXiv2018

Topological pseudodefects of a supersymmetric $SO(10)$ model and cosmology

Obtaining realistic supersymmetry preserving vacua in the minimal renormalizable supersymmetric $Spin(10)$ GUT model introduces considerations of the non-trivial topology of the vacuum manifold. The $D$-parity of low energy unification schemes gets lifted to a one-parameter subgroup $U(1)_D$ of $Spin(10)$. Yet, the choice of the fields signaling spontaneous symmetry breaking leads to disconnected subsets in the vacuum manifold related by the $D$-parity. The resulting domain walls, existing due to topological reasons but not stable, are identified as topological pseudodefects. We obtain a class of one-parameter paths connecting $D$-parity flipped vacua and compute the energy barrier height along the same. We consider the various patterns of symmetry breaking which can result in either intermediate scale gauge groups or a supersymmetric extension of the Standard Model. If the onset of inflation is subsequent to GUT breaking, as could happen also if inflation is naturally explained by the same GUT, the existence of such pseudodefects can leave signatures in the CMB. Specifically, this could have an impact on the scale invariance of the CMB fluctuations and LSS data at the largest scale.

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arXiv2018

No-scale SUGRA Inflation and Type-I seesaw

We show that MSSM with three right handed neutrinos incorporating a renormalizable Type-I seesaw superpotential and no-scale SURGA Kähler potential can lead to a Starobinsky kind of inflation potential along a flat direction associated with gauge invariant combination of Higgs, slepton and right handed sneutrino superfields. The inflation conditions put constraints on the Dirac Yukawa coupling and the Majorana masses required for the neutrino masses and also demands the tuning among the parameters. The scale of inflation is set by the mass of the heaviest right handed neutrino. We also fit the neutrino data from oscillation experiments at low scale using the effective RGEs of MSSM with three right handed neutrinos.

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arXiv2017

Electroweak vacuum stability in presence of singlet scalar dark matter in TeV scale seesaw models

We consider singlet extensions of the standard model, both in the fermion and the scalar sector, to account for the generation of neutrino mass at the TeV scale and the existence of dark matter respectively. For the neutrino sector we consider models with extra singlet fermions which can generate neutrino mass via the so called inverse or linear seesaw mechanism whereas a singlet scalar is introduced as the candidate for dark matter. We show that although these two sectors are disconnected at low energy, the coupling constants of both the sectors get correlated at high energy scale by the constraints coming from the perturbativity and stability/metastability of the electroweak vacuum. The singlet fermions try to destabilize the electroweak vacuum while the singlet scalar aids the stability. As an upshot, the electroweak vacuum may attain absolute stability even upto the Planck scale for suitable values of the parameters. We delineate the parameter space for the singlet fermion and the scalar couplings for which the electroweak vacuum remains stable/metastable and at the same time giving the correct relic density and neutrino masses and mixing angles as observed.

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arXiv2015

No scale SUGRA SO(10) derived Starobinsky Model of Inflation

We show that a supersymmetric renormalizable theory based on gauge group SO(10) and Higgs system {\bf {10 $\oplus$ 210 $\oplus$ 126 $\oplus$ $\overline{\bf 126}$}} with no scale supergravity can lead to a Starobinsky kind of potential for inflation. Successful inflation is possible in the cases where the potential during inflation corresponds to $SU(3)_C \times SU(2)_L \times SU(2)_R \times U(1)_{B-L}$, $SU(5)\times U(1)$ and flipped $SU(5)\times U(1)$ intermediate symmetry with a suitable choice of superpotential parameters. The reheating in such a scenario can occur via non perturbative decay of inflaton i.e. through "preheating". After the end of reheating, when universe cools down, the finite temperature potential can have a minimum which corresponds to MSSM.

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arXiv2015

New minimal supersymmetric SO(10) GUT phenomenology and its cosmological implications

Supersymmetric GUTs based on SO(10) gauge group are leading contenders to describe particle physics beyond the Standard Model. Among these the "New minimal supersymmetric SO(10) grand unified theory" (NMSGUT) based on Higgs system 10+120+210+126+$\overline{126}$ has been developing since 1982. It now successfully fits the whole standard Model gauge coupling, symmetry breaking and fermion mass-mixing data as well as the neutrino mass and mixing data in terms of NMSGUT parameters and just 6 soft supersymmetry breaking parameters defined at the GUT scale. In this thesis we study the phenomenology of NMSGUT, its implications for inflationary and Cold Dark matter cosmology and develop Renormalization group(RG) equations for the flow of NMSGUT couplings in the extreme ultraviolet. In the first part we show that superheavy threshold effects can drastically lower the SO(10) yukawa couplings required for realistic unification and this cures the long standing problem of fast proton decay in Susy GUT. Then we propose a novel Supersymmetric Seesaw inflection(SSI) scenario based upon a SU(2)_L x U(1)_R x U(1)_{B-L} invariant model, where the inflation mass is controlled by the large conjugate sneutrino mass. We show that it is much less fine-tuned and more stable than Dirac sneutrino based MSSM inflation. NMSGUT can embed SSI, and even provide a large tensor scalar ratio, but obstacles in achieving enough inflation remain. The NMSGUT Bino LSP is a good dark matter candidate when it can co-annihilate with a nearly degenerate sfermion as in fits with a light smuon. We also calculate two loop NMSGUT gauge-Yukawa Renormalization Group(RG) beta functions and show that GUT scale negative Higgs mass squared parameters required by NMSGUT fits can arise by RG flows from positive values at the Planck scale.

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arXiv2014

Baryon Stability on the Higgs Dissolution Edge : Threshold corrections and suppression of Baryon violation in the NMSGUT

Superheavy threshold corrections to the matching condition between matter Yukawa couplings of the effective Minimal Supersymmetric Standard Model (MSSM) and the New Minimal Supersymmetric (SO(10)) GUT(NMSGUT) provide a novel and generic mechanism for reducing the long standing and generically problematic operator dimension 5 Baryon decay rates. In suitable regions of the parameter space strong wave function renormalization of the effective MSSM Higgs doublets due to the large number of heavy fields can take the wave function renormalization of the MSSM Higgs field close to the dissolution value ($Z_{H,\overline{H}}=0$). Rescaling to canonical kinetic terms lowers the SO(10) Yukawas required to match the MSSM fermion data. Since the same Yukawas determine the dimension 5 B violation operator coefficients, the associated rates can be suppressed to levels compatible with current limits. Including these threshold effects also relaxes the constraint $ y_b-y_τ\simeq y_s-y_μ$ operative between $\textbf{10} -\textbf{120} $ plet generated tree level MSSM matter fermion Yukawas $y_f$. We exhibit accurate fits of the MSSM fermion mass-mixing data in terms of NMSGUT superpotential couplings and 5 independent soft Susy breaking parameters specified at $10^{16.25}\,$ GeV with the claimed suppression of Baryon decay rates. As before, our s-spectra are of the mini split supersymmetry type with large $|A_0|,μ,m_{H,\overline H} > 100\,\,$ TeV, light gauginos and normal s-hierarchy. Large $A_0,μ$ and soft masses allow significant deviation from the canonical GUT gaugino mass ratios and ensure vacuum safety. Even without optimization, prominent candidates for BSM discovery such as the muon magnetic anomaly, $b\rightarrow sγ$ and Lepto-genesis CP violation emerge in the preferred ball park.

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arXiv2012

Supersymmetric Seesaw Inflation

Supersymmetric Unified theories which incorporate a renormalizable Type I seesaw mechanism for small neutrino masses can also provide slow roll inflection point inflation along a flat direction associated with a gauge invariant combination of the Higgs, slepton and right handed sneutrino superfields. Inflationary parameters are related to the Majorana and Dirac couplings responsible for neutrino masses with the scale of inflation set by a right-handed neutrino mass $M_{ν^c} \sim 10^6-10^{12}$ GeV. Tuning of the neutrino Dirac and Majorana superpotential couplings and soft Susy breaking parameters is required to enforce flatness of the inflationary potential. In contrast to previous inflection point inflation models the cubic term is dominantly derived from superpotential couplings rather than soft A-terms. Thus since $M_{ν^c}>>M_{Susy}$ the tuning condition is almost independent of the soft supersymmetry breaking parameters and therefore more stable. The required fine tuning is also less stringent than for Minimal SUSY Standard Model (MSSM) inflation or Dirac neutrino 'A-term" inflation scenarios due to the much larger value of the inflaton mass. Reheating proceeds via `instant preheating' which rapidly dumps all the inflaton energy into a MSSM mode radiation bath giving a high reheat temperature $T_{rh} \approx M_{ν^c}^{3/4}\, 10^{6}$ GeV $\sim 10^{11}- 10^{15} $ GeV. Thus our scenario requires large gravitino mass $> 50 $ TeV to avoid a gravitino problem. The `instant preheating' and Higgs component of the inflaton also imply a `non-thermal' contribution to Leptogenesis due to facilitated production of right handed neutrinos during inflaton decay. We derive the tuning conditions for the scenario to work in the realistic New Minimal Supersymmetric SO(10) GUT and show that they can be satisfied by realistic fits.

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