61,438 research outputs found
Lower Limits on Soft Supersymmetry-Breaking Scalar Masses
Working in the context of the CMSSM, we argue that phenomenological
constraints now require the universal soft supersymmetry-breaking scalar mass
m_0 be non-zero at the input GUT scale. This conclusion is primarily imposed by
the LEP lower limit on the Higgs mass and the requirement that the lightest
supersymmetric particle not be charged. We find that m_0 > 0 for all tan beta
if mu 0 only when tan beta sim 8 and
one allows an uncertainty of 3+ GeV in the theoretical calculation of the Higgs
mass. Upper limits on flavour-changing neutral interactions in the MSSM squark
sector allow substantial violations of non-universality in the m_0 values, even
if their magnitudes are comparable to the lower limit we find in the CMSSM.
Also, we show that our lower limit on m_0 at the GUT scale in the CMSSM is
compatible with the no-scale boundary condition m_0 = 0 at the Planck scale.Comment: 11 pages, latex, 6 eps figure
More on Electric Dipole Moment Constraints on Phases in the Constrained MSSM
We reconsider constraints on \cp-violating phases in the Constrained
Minimal Supersymmetric Standard Model. We include the recent calculations of
Ibrahim and Nath on the chromoelectric and purely gluonic contributions to the
quark electric dipole moment and combine cosmological limits on gaugino masses
with experimental bounds on the neutron (and electron) electric dipole moments.
The constraint on the phase of the Higgs mixing mass , |\thm|, is
dependent on the value of the trilinear mass parameter, , in the model and
on . For values of |A| < 300 \gev at the GUT scale, we find
|\thm|/\pi \la 0.05, while for |A| < 1500 \gev, |\thm|/\pi \la 0.3. Thus,
we find that in principle, large CP violating phases are compatible with the
bounds on the electric dipole moments of the neutron and electron, as well as
remaining compatible with the cosmological upper bound on the relic density of
neutralinos. The other \cp-violating phase \tha is essentially
unconstrained.Comment: 11 pages in LaTeX + 4 postscript figures, uses epsf.sty. Added two
references, clarified figures. Accepted to Physics Letter
Supersymmetric Dark Matter Candidates
After reviewing the theoretical, phenomenological and experimental
motivations for supersymmetric extensions of the Standard Model, we recall that
supersymmetric relics from the Big Bang are expected in models that conserve R
parity. We then discuss possible supersymmetric dark matter candidates,
focusing on the lightest neutralino and the gravitino. In the latter case, the
next-to-lightest supersymmetric particle is expected to be long-lived, and
possible candidates include spartners of the tau lepton, top quark and
neutrino. We then discuss the roles of the renormalization-group equations and
electroweak symmetry breaking in delimiting the supersymmetric parameter space.
We discuss in particular the constrained minimal extension of the Standard
Model (CMSSM), in which the supersymmetry-breaking parameters are assumed to be
universal at the grand unification scale, presenting predictions from a
frequentist analysis of its parameter space. We also discuss astrophysical and
cosmological constraints on gravitino dark matter models, as well as the
parameter space of minimal supergravity (mSUGRA) models in which there are
extra relations between the trilinear and bilinear supersymmetry-breaking
parameters, and between the gravitino and scalar masses. Finally, we discuss
models with non-universal supersymmetry-breaking contributions to Higgs masses,
and models in which the supersymmetry-breaking parameters are universal at some
scale below that of grand unification.
http://cambridge.org/us/catalogue/catalogue.asp?isbn=9780521763684Comment: 38 pages, 10 figure
A Note on Infinities in Eternal Inflation
In some well-known scenarios of open-universe eternal inflation, developed by
Vilenkin and co-workers, a large number of universes nucleate and thermalize
within the eternally inflating mega-universe. According to the proposal, each
universe nucleates at a point, and therefore the boundary of the nucleated
universe is a space-like surface nearly coincident with the future light cone
emanating from the point of nucleation, all points of which have the same
proper-time. This leads the authors to conclude that at the proper-time t =
t_{nuc} at which any such nucleation occurs, an infinite open universe comes
into existence. We point out that this is due entirely to the supposition of
the nucleation occurring at a single point, which in light of quantum cosmology
seems difficult to support. Even an infinitesimal space-like length at the
moment of nucleation gives a rather different result -- the boundary of the
nucleating universe evolves in proper-time and becomes infinite only in an
infinite time. The alleged infinity is never attained at any finite time.Comment: 13 pages and 6 figure
Persistent homology of groups
We introduce and investigate notions of persistent homology for p-groups and
for coclass trees of p-groups. Using computer techniques we show that
persistent homology provides fairly strong homological invariants for p-groups
of order at most 81. The strength of these invariants, and some elementary
theoretical properties, suggest that persistent homology may be a useful tool
in the study of prime-power groups.Comment: 12 pages, 6 figure
A Penrose polynomial for embedded graphs
We extend the Penrose polynomial, originally defined only for plane graphs,
to graphs embedded in arbitrary surfaces. Considering this Penrose polynomial
of embedded graphs leads to new identities and relations for the Penrose
polynomial which can not be realized within the class of plane graphs. In
particular, by exploiting connections with the transition polynomial and the
ribbon group action, we find a deletion-contraction-type relation for the
Penrose polynomial. We relate the Penrose polynomial of an orientable
checkerboard colourable graph to the circuit partition polynomial of its medial
graph and use this to find new combinatorial interpretations of the Penrose
polynomial. We also show that the Penrose polynomial of a plane graph G can be
expressed as a sum of chromatic polynomials of twisted duals of G. This allows
us to obtain a new reformulation of the Four Colour Theorem
- …