2,032 research outputs found
Particle Physics at Future Colliders
The search for physics beyond the Standard Model motivates new high-energy accelerators, which will require high luminosities in order to produce interesting new heavy particles. Using the Higgs boson and supersymmetry as examples, we discuss the capabilities of the LHC and linear colliders in the TeV and multi-TeV energy ranges to discover and study new particles
Into a New World of Physics and Symmetry
CERN theorist John Ellis charts the LHCâs voyage to a New World of discovery, exploring physics at the TeV scale with the capacity to create new forms of matter
D-Brane Recoil Mislays Information
We discuss the scattering of a light closed-string state off a brane,
taking into account quantum recoil effects on the latter, which are described
by a pair of logarithmic operators. The light-particle and -brane subsystems
may each be described by a world-sheet with an external source due to the
interaction between them. This perturbs each subsystem away from criticality,
which is compensated by dressing with a Liouville field whose zero mode we
interpret as time. The resulting evolution equations for the brane and the
closed string are of Fokker-Planck and modified quantum Liouville type,
respectively. The apparent entropy of each subsystem increases as a result of
the interaction between them, which we interpret as the loss of information
resulting from non-observation of the other entangled subsystem. We speculate
on the possible implications of these results for the propagation of closed
strings through a dilute gas of virtual branes.Comment: 34 pages, LaTeX, 2 figures (included
Asymptotic behavior of the finite-size magnetization as a function of the speed of approach to criticality
The main focus of this paper is to determine whether the thermodynamic
magnetization is a physically relevant estimator of the finite-size
magnetization. This is done by comparing the asymptotic behaviors of these two
quantities along parameter sequences converging to either a second-order point
or the tricritical point in the mean-field Blume--Capel model. We show that the
thermodynamic magnetization and the finite-size magnetization are asymptotic
when the parameter governing the speed at which the sequence
approaches criticality is below a certain threshold . However, when
exceeds , the thermodynamic magnetization converges to 0
much faster than the finite-size magnetization. The asymptotic behavior of the
finite-size magnetization is proved via a moderate deviation principle when
.
To the best of our knowledge, our results are the first rigorous confirmation
of the statistical mechanical theory of finite-size scaling for a mean-field
model.Comment: Published in at http://dx.doi.org/10.1214/10-AAP679 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Ginzburg-Landau Polynomials and the Asymptotic Behavior of the Magnetization Near Critical and Tricritical Points
For the mean-field version of an important lattice-spin model due to Blume
and Capel, we prove unexpected connections among the asymptotic behavior of the
magnetization, the structure of the phase transitions, and a class of
polynomials that we call the Ginzburg-Landau polynomials. The model depends on
the parameters n, beta, and K, which represent, respectively, the number of
spins, the inverse temperature, and the interaction strength. Our main focus is
on the asymptotic behavior of the magnetization m(beta_n,K_n) for appropriate
sequences (beta_n,K_n) that converge to a second-order point or to the
tricritical point of the model and that lie inside various subsets of the
phase-coexistence region. The main result states that as (beta_n,K_n) converges
to one of these points (beta,K), m(beta_n,K_n) ~ c |beta - beta_n|^gamma --> 0.
In this formula gamma is a positive constant, and c is the unique positive,
global minimum point of a certain polynomial g that we call the Ginzburg-Landau
polynomial. This polynomial arises as a limit of appropriately scaled
free-energy functionals, the global minimum points of which define the
phase-transition structure of the model. For each sequence (beta_n,K_n) under
study, the structure of the global minimum points of the associated
Ginzburg-Landau polynomial mirrors the structure of the global minimum points
of the free-energy functional in the region through which (beta_n,K_n) passes
and thus reflects the phase-transition structure of the model in that region.
The properties of the Ginzburg-Landau polynomials make rigorous the predictions
of the Ginzburg-Landau phenomenology of critical phenomena, and the asymptotic
formula for m(beta_n,K_n) makes rigorous the heuristic scaling theory of the
tricritical point.Comment: 70 pages, 8 figure
New physics with the compact linear collider
Probing beyond the established picture of particle physics will require some radical rethinking of accelerator designs. If accelerators are to reach the ever-higher energies that theorists would dearly like to see explored, the technological spin-offs of this engineering feat could be as surprising as the new subatomic physics
Options for Gauge Groups in Five-Dimensional Supergravity
Motivated by the possibility that physics may be effectively five-dimensional over some range of distance scales, we study the possible gaugings of five-dimensional N=2 supergravity. Using a constructive approach, we derive the conditions that must be satisfied by the scalar fields in the vector, tensor and hypermultiplets if a given global symmetry is to be gaugeable. We classify all those theories that admit the gauging of a compact group that is either Abelian or semi-simple, or a direct product of a semi-simple and an Abelian group. In the absence of tensor multiplets, either the gauge group must be semi-simple or the Abelian part has to be U(1)_R and/or an Abelian isometry of the hyperscalar manifold. On the other hand, in the presence of tensor multiplets the gauge group cannot be semi-simple. As an illustrative exercise, we show how the Standard Model SU(3) X SU(2) X U(1) group may be gauged in five-dimensional N=2 supergravity. We also show how previous special results may be recovered within our general formalism
Pursuing the Strange Stop Interpretation of the HERA Large data
We explore the possible interpretation of the large- anomaly reported by the H1 and ZEUS collaborations in terms of stop squark production off a strange quark in the proton via an R-violating interaction. This "strange stop" interpretation is constrained by LEP measurements of the decay rate in addition to constraints from the electroweak parameter and CDF and D0 searches for first-generation leptoquarks. We investigate the interplay between these constraints, taking full account of stop mixing effects. We find that if GeV only relatively small domains of the chargino and neutralino parameters are consistent with these constraints, and explore the extent to which this scenario may be probed further by searches for contact interactions at LEP~2 and experiments with and polarized beams at HERA
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