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T. Banks

Publications and source records attributed to T. Banks.

At least 73 records · Page 4Linked to original sources
arXiv2012

Arguments Against a Finite N=8 Supergravity

I present arguments based on dispersion theory and the existence of charged BPS states of small charge, that maximally supersymmetric SUGRA is not a finite theory. The essence of the argument is that the perturbative construction of the theory implies that scattering amplitudes are invariant under a continuous SU(8) global symmetry, which is broken by contributions from virtual BPS states. Conventional estimates of the contributions of those states above production threshold, shows that they should be order one. If the amplitude satisfies a dispersion relation with a finite number of subtractions, as has recently been argued by Giddings and Porto [1], then SU(8) violating amplitudes appear at finite orders in the low energy expansion. We also make a brief remark about the inconsistency of the idea of classicalization in non-gravitational theories.

hep-th↗
arXiv2011

Holographic Space-Time: The Takeaway

The theory of holographic space-time (HST) generalizes both string theory and quantum field theory. It provides a geometric rationale for supersymmetry (SUSY) and a formalism in which super-Poincare invariance follows from Poincare invariance. HST unifies particles and black holes, realizing both as excitations of non-commutative geometrical variables on a holographic screen. Compact extra dimensions are interpreted as finite dimensional unitary representations of super-algebras, and have no moduli. Full field theoretic Fock spaces, and continuous moduli are both emergent phenomena of super-Poincare invariant limits in which the number of holographic degrees of freedom goes to infinity. Finite radius de Sitter (dS) spaces have no moduli, and break SUSY with a gravitino mass scaling like $Λ^{1/4}$. We present a holographic theory of inflation and fluctuations. The inflaton field is an emergent concept, describing the geometry of an underlying HST model, rather than "a field associated with a microscopic string theory". We argue that the phrase in quotes is meaningless in the HST formalism.

hep-th↗
arXiv2010

Holographic space-time and its phenomenological implications

I briefly review the theory of Holographic Space-time and its relation to the cosmological constant problem, and the breaking of supersymmetry (SUSY). When combined with some simple phenomenological requirements, these ideas lead to a fairly unique model for Tera-scale physics, which implies direct gauge mediation of SUSY breaking and a model for dark matter as a hidden sector baryon, with nonzero magnetic dipole moment.

hep-th↗
arXiv2009

Locality and the classical limit of quantum systems

I argue that conventional estimates of the criterion for classical behavior of a macroscopic body are incorrect in most circumstances,because they do not take into account the locality of interactions, which characterizes the behavior of all systems described approximately by local quantum field theory. The deviations from classical behavior of a macroscopic body, except for those that can be described as classical uncertainties in the initial values of macroscopic variables,are {\it exponentially} small as a function of the volume of the macro-system in microscopic units. Conventional estimates are correct only when the internal degrees of freedom of the macrosystem are in their ground state, and the classical motion of collective coordinates is adiabatic. Otherwise, the system acts as its own environment and washes out quantum phase correlations between different classical states of its collective coordinates. I suggest that it is likely that we can only achieve meso-scopic superpositions, for systems which have topological variables, and for which we can couple to those variables without exciting phonons.

quant-ph↗
arXiv2008

Holographic Space-time from the Big Bang to the de Sitter era

I review the holographic theory of space-time and its applications to cosmology. Much of this has appeared before, but the discussion is more unified and concise. I also include some material on work in progress, whose aim is to understand compactification in terms of finite dimensional super-algebras. This is an expanded version of a lecture I gave at the conference on Liouville Quantum Gravity and Statistical Systems, in memory of Alexei Zamolodchikov, at the Poncelet Institute in Moscow, 21-24 June, 2008.

hep-th↗
arXiv2008

Locality and the classical limit of quantum mechanics

I argue that conventional estimates of the criterion for classical behavior of a macroscopic body are incorrect, because they do not take into account the locality of interactions, which characterizes the behavior of all systems described approximately by local quantum field theory. Black holes are the only localized objects which do not have such a description. The deviations from classical behavior of a macroscopic body, except for those which can be described as classical uncertainties in the initial values of macroscopic variables,are {\it exponentially} small as a function of the volume of the macro-system in microscopic units.

quant-ph↗
arXiv2007

Embedding the Pentagon

The Pentagon Model is an explicit supersymmetric extension of the Standard Model, which involves a new strongly-interacting SU(5) gauge theory at TeV-scale energies. We show that the Pentagon can be embedded into an SU(5) x SU(5) x SU(5) gauge group at the GUT scale. The doublet-triplet splitting problem, and proton decay compatible with experimental bounds, can be successfully addressed in this context. The simplest approach fails to provide masses for the lighter two generations of quarks and leptons; however, this problem can be solved by the addition of a pair of antisymmetric tensor fields and an axion.

hep-th↗
arXiv2007

Massive IIA flux compactifications and U-dualities

We attempt to find a rigorous formulation for the massive type IIA orientifold compactifications of string theory introduced in hep-th/0505160. An approximate double T-duality converts this background into IIA string theory on a twisted torus, but various arguments indicate that the back reaction of the orientifold on this geometry is large. In particular, an AdS calculation of the entropy suggests a scaling appropriate for N M2-branes, in a certain limit of the compactification, though not the one studied in hep-th/0505160. The M-theory lift of this specific regime is not 4 dimensional. We suggest that the generic limit of the background corresponds to a situation analogous to F-theory, where the string coupling is small in some regions of a compact geometry, and large in others, so that neither a long wavelength 11D SUGRA expansion, nor a world sheet expansion exists for these compactifications. We end with a speculation on the nature of the generic compactification.

hep-th↗
arXiv2007

Entropy and initial conditions in cosmology

I discuss the Boltzmann-Penrose question of why the initial conditions for cosmology have low entropy. The modern version of Boltzmann's answer to this question, due to Dyson, Kleban and Susskind, seems to imply that the typical intelligent observer arises through thermal fluctuation, rather than cosmology and evolution. I investigate whether this can be resolved within the string landscape. I end with a review of the suggestion that Holographic Cosmology provides a simpler answer to the problem. This paper is a revision of unpublished work from the spring of 2006, combined with my talk at the Madrid conference on String theory and Cosmology, Nov 2006.

hep-th↗
arXiv2006

Baryogenesis, Dark Matter and the Pentagon

We present a new mechanism for baryogenesis, which links the baryon asymmetry of the universe to the dark matter density. The mechanism arises naturally in the Pentagon model of TeV scale physics. In that context, it forces a re-evaluation of some of the assumptions of the model, and we detail the changes that are required in order to fit observations.

hep-ph↗
arXiv2006

Towards a quantum theory of de Sitter space

We describe progress towards constructing a quantum theory of de Sitter space in four dimensions. In particular we indicate how both particle states and Schwarzschild de Sitter black holes can arise as excitations in a theory of a finite number of fermionic oscillators. The results about particle states depend on a conjecture about algebras of Grassmann variables, which we state, but do not prove.

hep-th↗
arXiv2006

Space-like Singularities and Thermalization

We conjecture that space-like singularities are simply regions in which all available degrees of freedom are excited, and the system cycles randomly through generic quantum states in its Hilbert space. There is no simple geometric description of the interior of such a region, but if it is embedded in a semi-classical space-time an external observer sees it as a black hole. Big Bang and Crunch singularities, for which there is no such embedding, must be described in purely quantum terms. We present several possible descriptions of such cosmologies.

hep-th↗
arXiv2006

II_{\infty} Factors and M-theory in Asymptotically Flat Space-Time

I discuss a formulation of M-theory at null infinity, which is based on general principles of holographic space-time, and is manifestly covariant. The construction utilizes a certain Type II Von Neumann algebra, which provides a kinematic framework, alternative to Fock Space, for describing the scattering states of eleven dimensional asymptotically flat M-theory. The construction provides a greatly clarified statement of the connection between SUSY and holography. I make preliminary remarks about dynamical equations for the S-matrix, and compactifications.

hep-th↗
arXiv2006

Remodeling the Pentagon After the Events of 2/23/06

The meta-stable SUSY breaking mechanism of Intriligator Seiberg and Shih can be used to simplify the Pentagon model of TeV scale physics. The simplified model has only a single scalar field and no troublesome low energy axion. One significant signature is $l^+ l^- X$ plus missing energy, where $X$ might be the two photons of gauge mediated models, but is likely to be different. There is a new strongly interacting sector with a scale around 1.5 TeV. The penta-hadrons of this sector have masses of order 6 TeV or more. Dark matter is probably the pseudo-goldstone boson of spontaneously broken penta-baryon number. This can be a viable dark matter candidate if an appropriate asymmetry in penta-baryon number is generated in the early universe. The pseudo-Goldstone particle has a mass of $\sim 1$ eV and is produced predominantly in flavor changing charged current decays of ordinary particles. The model solves the flavor problems of SUSY, but has two low energy CP violating phases, whose value is strongly constrained by experiment.

hep-ph↗
arXiv2006

Regulating Eternal Inflation II: The Great Divide

In a previous paper, two of the authors presented a "regulated" picture of eternal inflation. This picture both suggested and drew support from a conjectured discontinuity in the amplitude for tunneling from positive to negative vacuum energy, as the positive vacuum energy was sent to zero; analytic and numerical arguments supporting this conjecture were given. Here we show that this conjecture is false, but in an interesting way. There are no cases where tunneling amplitudes are discontinuous at vanishing cosmological constant; rather, the space of potentials separates into two regions. In one region decay is strongly suppressed, and the proposed picture of eternal inflation remains viable; sending the (false) vacuum energy to zero in this region results in an absolutely stable asymptotically flat space. In the other region, we argue that the space-time at vanishing cosmological constant is unstable, but not asymptotically Minkowski. The consequences of our results for theories of supersymmetry breaking are unchanged.

hep-th↗
arXiv2005

Regulating Eternal Inflation

We present an interpretation of the physics of space-times undergoing eternal inflation by repeated nucleation of bubbles. In many cases the physics can be interpreted in terms of the quantum mechanics of a system with a finite number of states. If this interpretation is correct, the conventional picture of these space-times is misleading.

hep-th↗
arXiv2005

Cosmological Supersymmetry Breaking and the Power of the Pentagon: A Model of Low Energy Particle Physics

I present a low energy Lagrangian implementing the idea of Cosmological SUSY breaking (CSB). The model predicts ${\rm tan}β\sim 1$, and incorporates a new mechanism for breaking of $SU(2)\times U(1)$. The Higgs mass is determined by new physics and can evade the bounds of the MSSM. The model resolves the CP and flavor problems of SUSY. The up quark mass is non-vanishing. An axion-like particle, with TeV scale decay constant, appears inevitably. Such a particle is experimentally ruled out if it has conventional QCD axion couplings. The problem {\it may} be avoided by adding dimension 5 operators, which explicitly break the axial symmetry, but this probably introduces a strong CP problem.

hep-ph↗