59,060 research outputs found
Affine maps of density matrices
For quantum systems described by finite matrices, linear and affine maps of
matrices are shown to provide equivalent descriptions of evolution of density
matrices for a subsystem caused by unitary Hamiltonian evolution in a larger
system; an affine map can be replaced by a linear map, and a linear map can be
replaced by an affine map. There may be significant advantage in using an
affine map. The linear map is generally not completely positive, but the linear
part of an equivalent affine map can be chosen to be completely positive and
related in the simplest possible way to the unitary Hamiltonian evolution in
the larger system.Comment: 4 pages, title changed, sentence added, reference update
Sparticle masses in deflected mirage mediation
We discuss the sparticle mass patterns that can be realized in deflected
mirage mediation scenario of supersymmetry breaking, in which the moduli,
anomaly, and gauge mediations all contribute to the MSSM soft parameters.
Analytic expression of low energy soft parameters and also the sfermion mass
sum rules are derived, which can be used to interpret the experimentally
measured sparticle masses within the framework of the most general mixed
moduli-gauge-anomaly mediation. Phenomenological aspects of some specific
examples are also discussed.Comment: 43 pages, 17 figures, references adde
Gaugino and Scalar Masses in the Landscape
In this letter we demonstrate the genericity of suppressed gaugino masses M_a
\sim m_{3/2}/ln(M_P/m_{3/2}) in the IIB string landscape, by showing that this
relation holds for D7-brane gauginos whenever the associated modulus is
stabilised by nonperturbative effects. Although m_{3/2} and M_a take many
different values across the landscape, the above small mass hierarchy is
maintained. We show that it is valid for models with an arbitrary number of
moduli and applies to both the KKLT and exponentially large volume approaches
to Kahler moduli stabilisation. In the latter case we explicitly calculate
gaugino and moduli masses for compactifications on the two-modulus Calabi-Yau
P^4_[1,1,1,6,9]. In the large-volume scenario we also show that soft scalar
masses are approximately universal with m_i^2 \sim m_{3/2}^2 (1 + \epsilon_i),
with the non-universality parametrised by \epsilon_i \sim 1/ln (M_P/m_{3/2})^2
\sim 1/1000. We briefly discuss possible phenomenological implications of our
results.Comment: 15 pages, JHEP style; v2. reference adde
Sudden death of effective entanglement
Sudden death of entanglement is a well-known effect resulting from the finite
volume of separable states. We study the case when the observer has a limited
measurement capability and analyse the effective entanglement, i.e.
entanglement minimized over the output data. We show that in the well defined
system of two quantum dots monitored by single electron transistors, one may
observe a sudden death of effective entanglement when real, physical
entanglement is still alive. For certain measurement setups, this occurs even
for initial states for which sudden death of physical entanglement is not
possible at all. The principles of the analysis may be applied to other
analogous scenarios, such as etimation of the parameters arising from quantum
process tomography.Comment: final version, 5 pages, 3 figure
String or M theory axion as a quintessence
A slow-rolling scalar field ( Quintessence) with potential energy
has been proposed as the origin of
accelerating universe at present. We investigate the effective potential of
in the framework of supergravity model including the quantum corrections
induced by generic (nonrenormalizable) couplings of to the gauge and
charged matter multiplets. It is argued that the K\"ahler potential,
superpotential and gauge kinetic functions of the underlying supergravity model
are required to be invariant under the variation of with an extremely fine
accuracy in order to provide a working quintessence potential. Applying these
results for string or -theory, we point out that the heterotic -theory or
Type I string axion can be a plausible candidate for quintessence if (i) it
does not couple to the instanton number of gauge interactions not weaker than
those of the standard model and (ii) the modulus partner of the
periodic quintessence axion has a large VEV:
. It is stressed
that such a large gives the gauge unification scale at around the
phenomenologically favored value GeV. To provide an
accelerating universe, the quintessence axion should be at near the top of its
effective potential at present, which requires a severe fine tuning of the
initial condition of and in the early universe. We discuss a late
time inflation scenario based on the modular and CP invariance of the moduli
effective potential, yielding the required initial condition in a natural
manner if the K\"ahler metric of the quintessence axion superfield receives a
sizable nonperturbative contribution.Comment: 23 pages, 3 figures, version to be published at Phys. Rev.
Four-Dimensional Effective Supergravity and Soft Terms in M-Theory
We provide a simple macroscopic analysis of the four-dimensional effective
supergravity of the Ho\v{r}ava-Witten M-theory which is expanded in powers of
and where ,
and denote the eleven-dimensional gravitational coupling, the
Calabi-Yau volume and the eleventh length respectively. Possible higher order
terms in the K\"ahler potential are identified and matched with the heterotic
string corrections. In the context of this M-theory expansion, we analyze the
soft supersymmetry-breaking terms under the assumption that supersymmetry is
spontaneously broken by the auxiliary components of the bulk moduli
superfields. It is examined how the pattern of soft terms changes when one
moves from the weakly coupled heterotic string limit to the M-theory limit.Comment: Latex, 23 pages, 3 figures. References are added and the discussion
of the M-theory expansion parameters is enlarge
Relation between Kitaev magnetism and structure in -RuCl
Raman scattering has been employed to investigate lattice and magnetic
excitations of the honeycomb Kitaev material -RuCl and its
Heisenberg counterpart CrCl. Our phonon Raman spectra give evidence for a
first-order structural transition from a monoclinic to a rhombohedral structure
for both compounds. Significantly, only -RuCl features a large
thermal hysteresis, consistent with the formation of a wide phase of
coexistence. In the related temperature interval of K, we observe a
hysteretic behavior of magnetic excitations as well. The stronger magnetic
response in the rhombohedral compared to the monoclinic phase evidences a
coupling between the crystallographic structure and low-energy magnetic
response. Our results demonstrate that the Kitaev magnetism concomitant with
fractionalized excitations is susceptible to small variations of bonding
geometry.Comment: 9 pages, 8 figures, To appear in PR
Dynamical solution to the problem at TeV scale
We introduce a new confining force (\mu-color) at TeV scale to dynamically
generate a supersymmetry preserving mass scale which would replace the \mu
parameter in the minimal supersymmetric standard model (MSSM). We discuss the
Higgs phenomenology and also the pattern of soft supersymmetry breaking
parameters allowing the correct electroweak symmetry breaking within the
\mu-color model, which have quite distinctive features from the MSSM and also
from other generalizations of the MSSM.Comment: 12 pages, REVte
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