Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userWhere is String Theory?
61
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We use the S-matrix bootstrap to carve out the space of unitary, crossing symmetric and supersymmetric graviton scattering amplitudes in ten dimensions. We focus on the leading Wilson coefficient $alpha$ controlling the leading correction to maximal supergravity. The negative region $alpha<0$ is excluded by a simple dual argument based on linearized unitarity (the desert). A whole semi-infinite region $alpha gtrsim 0.14$ is allowed by the primal bootstrap (the garden). A finite intermediate region is excluded by non-perturbative unitarity (the swamp). Remarkably, string theory seems to cover all (or at least almost all) the garden from very large positive $alpha$ -- at weak coupling -- to the swamp boundary -- at strong coupling.
rate research
Read More
The energies of glue in the presence of a static quark-antiquark pair are calculated for separations r ranging from 0.1 fm to 4 fm and for various quark-antiquark orientations on the lattice. Our simulations use an improved gauge-field action on anisotropic space-time lattices. Discretization errors and finite volume effects are studied. We find that the spectrum does not exhibit the expected onset of the universal pi/r Goldstone excitations of the effective QCD string, even for r as large as 4 fm. Our results cast serious doubts on the validity of treating glue in terms of a fluctuating string for r below 2 fm. Retardation effects in the Upsilon system are also studied by comparing level splittings from the Born-Oppenheimer approximation with those directly obtained in simulations.
We consider two-dimensional Yang-Mills theories on arbitrary Riemann surfaces. We introduce a generalized Yang-Mills action, which coincides with the ordinary one on flat surfaces but differs from it in its coupling to two-dimensional gravity. The quantization of this theory in the unitary gauge can be consistently performed taking into account all the topological sectors arising from the gauge-fixing procedure. The resulting theory is naturally interpreted as a Matrix String Theory, that is as a theory of covering maps from a two-dimensional world-sheet to the target Riemann surface.
With no free parameter (except the string scale $M_S$), dynamical flux compactification in Type IIB string theory determines both the cosmological constant (vacuum energy density) $Lambda$ and the Planck mass $M_P$ in terms of $M_S$, thus yielding their relation. Following elementary probability theory, we find that a good fraction of the meta-stable de Sitter vacua in the cosmic string theory landscape tend to have an exponentially small cosmological constant $Lambda$ compared to either the string scale $M_S$ or the Planck scale $M_P$, i.e., $Lambda ll M_S^4 ll M_P^4$. Here we illustrate the basic stringy ideas with a simple scalar field $phi^3$ (or $phi^4$) model coupled with fluxes to show how this may happen and how the usual radiative instability problem is bypassed (since there are no parameters to be fine-tuned). These low lying semi-classical de Sitter vacua tend to be accompanied by light scalar bosons/axions, so the Higgs boson mass hierarchy problem may be ameliorated as well.
The direct searches for Superymmetry at colliders can be complemented by direct searches for dark matter (DM) in underground experiments, if one assumes the Lightest Supersymmetric Particle (LSP) provides the dark matter of the universe. It will be shown that within the Constrained minimal Supersymmetric Model (CMSSM) the direct searches for DM are complementary to direct LHC searches for SUSY and Higgs particles using analytical formulae. A combined excluded region from LHC, WMAP and XENON100 will be provided, showing that within the CMSSM gluinos below 1 TeV and LSP masses below 160 GeV are excluded (m_{1/2} > 400 GeV) independent of the squark masses.
We show that four-dimensional de Sitter space is a Glauber-Sudarshan state, i.e. a coherent state, over a supersymmetric solitonic background in full string theory. We argue that such a state is only realized in the presence of temporally varying degrees of freedom and including quantum corrections, with supersymmetry being broken spontaneously. On the other hand, fluctuations over the resulting de Sitter space is governed by the Agarwal-Tara state, which is a graviton (and flux)-added coherent state. Once de Sitter space is realized as a coherent state, and not as a vacuum, its ability to remain out of the swampland as well as issues regarding its (meta)stability, vacuum energy, and finite entropy appear to have clear resolutions.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
