1,138 research outputs found
Supersymmetry without the Desert
Naturalness of electroweak symmetry breaking in weak scale supersymmetric
theories may suggest the absence of the conventional supersymmetric desert. We
present a simple, realistic framework for supersymmetry in which (most of) the
virtues of the supersymmetric desert are naturally reproduced without having a
large energy interval above the weak scale. The successful supersymmetric
prediction for the low-energy gauge couplings is reproduced due to a gauged R
symmetry present in the effective theory at the weak scale. The observable
sector superpotential naturally takes the form of the next-to-minimal
supersymmetric standard model, but without being subject to the Landau pole
constraints up to the conventional unification scale. Supersymmetry breaking
masses are generated by the F-term and D-term VEVs of singlet and U(1)_R gauge
fields, as well as by anomaly mediation, at a scale not far above the weak
scale. We study the resulting patten of supersymmetry breaking masses in
detail, and find that it can be quite distinct. We construct classes of
explicit models within this framework, based on higher dimensional unified
theories with TeV-sized extra dimensions. A similar model based on a non-R
symmetry is also presented. These models have a rich phenomenology at the TeV
scale, and allow for detailed analyses of, e.g., electroweak symmetry breaking.Comment: 42 page
The Static Quantum Multiverse
We consider the multiverse in the intrinsically quantum mechanical framework
recently proposed in Refs. [1,2]. By requiring that the principles of quantum
mechanics are universally valid and that physical predictions do not depend on
the reference frame one chooses to describe the multiverse, we find that the
multiverse state must be static---in particular, the multiverse does not have a
beginning or end. We argue that, despite its naive appearance, this does not
contradict observation, including the fact that we observe that time flows in a
definite direction. Selecting the multiverse state is ultimately boiled down to
finding normalizable solutions to certain zero-eigenvalue equations, analogous
to the case of the hydrogen atom. Unambiguous physical predictions would then
follow, according to the rules of quantum mechanics.Comment: 27 pages, 2 figures; a typo in the abstract correcte
Magnetic field screening and mirroring in graphene
The orbital magnetism in spatially varying magnetic fields is studied in
monolayer graphene within the effective mass approximation. We find that,
unlike the conventional two-dimensional electron system, graphene with small
Fermi wave number k_F works as a magnetic shield where the field produced by a
magnetic object placed above graphene is always screened by a constant factor
on the other side of graphene. The object is repelled by a diamagnetic force
from the graphene, as if there exists its mirror image with a reduced amplitude
on the other side of graphene. The magnitude of the force is much greater than
that of conventional two-dimensional system. The effect disappears with the
increase of k_F.Comment: 5 pages, 3 figure
Warped Supersymmetric Unification with Non-Unified Superparticle Spectrum
We present a new supersymmetric extension of the standard model. The model is
constructed in warped space, with a unified bulk symmetry broken by boundary
conditions on both the Planck and TeV branes. In the supersymmetric limit, the
massless spectrum contains exotic colored particles along with the particle
content of the minimal supersymmetric standard model (MSSM). Nevertheless, the
model still reproduces the MSSM prediction for gauge coupling unification and
does not suffer from a proton decay problem. The exotic states acquire masses
from supersymmetry breaking, making the model completely viable, but there is
still the possibility that these states will be detected at the LHC. The
lightest of these states is most likely A_5^XY, the fifth component of the
gauge field associated with the broken unified symmetry. Because supersymmetry
is broken on the SU(5)-violating TeV brane, the gaugino masses generated at the
TeV scale are completely independent of one another. We explore some of the
unusual features that the superparticle spectrum might have as a consequence.Comment: 21 pages, Latex, version to appear in Phys. Rev.
More Visible Effects of the Hidden Sector
There is a growing appreciation that hidden sector dynamics may affect the
supersymmetry breaking parameters in the visible sector (supersymmetric
standard model), especially when the dynamics is strong and superconformal. We
point out that there are effects that have not been previously discussed in the
literature. For example, the gaugino masses are suppressed relative to the
gravitino mass. We discuss their implications in the context of various
mediation mechanisms. The issues discussed include anomaly mediation with
singlets, the mu (B mu) problem in gauge and gaugino mediation, and distinct
mass spectra for the superparticles that have not been previously considered.Comment: 25 pages; small clarifications and corrections, version to appear in
Phys. Rev.
The disintegrin echistatin in combination with doxorubicin targets high-metastatic human osteosarcoma overexpressing ανβ3 integrin in chick embryo and nude mouse models.
Echistatin, a cyclic RGD peptide, which is an antagonist of αvβ3 integrin (disintegrin), inhibited human osteosarcoma in the chick chorioallontoic membrane (CAM) model and tumor growth and pulmonary metastases in a nude mouse orthotopic model. A high-metastatic variant of human osteosarcoma, 143B-LM4, overexpressing αvβ3 integrin was used. Tumor angiogenesis by high-metastatic variant 143B-LM4 cells in the CAM was significantly inhibited by echistatin (P<0.05) as was overall growth. A doxorubicin (DOX)-echistatin combination inhibited orthotopic tumor growth compared to untreated control (P<0.01) or DOX alone (P<0.05) in nude mice. Tumor-bearing mice treated with the DOX-echistatin combination survived longer than those treated with DOX alone or control PBS (P<0.01 and P<0.01, respectively). Echistatin also inhibited experimental lung metastasis of 143B-LM4 cells in nude mice. These results suggest that DOX in combination with a disintegrin has potential to treat osteosarcoma and that αvβ3 integrin may be a target for osteosarcoma
Multiverse Understanding of Cosmological Coincidences
There is a deep cosmological mystery: although dependent on very different
underlying physics, the timescales of structure formation, of galaxy cooling
(both radiatively and against the CMB), and of vacuum domination do not differ
by many orders of magnitude, but are all comparable to the present age of the
universe. By scanning four landscape parameters simultaneously, we show that
this quadruple coincidence is resolved. We assume only that the statistical
distribution of parameter values in the multiverse grows towards certain
catastrophic boundaries we identify, across which there are drastic regime
changes. We find order-of-magnitude predictions for the cosmological constant,
the primordial density contrast, the temperature at matter-radiation equality,
the typical galaxy mass, and the age of the universe, in terms of the fine
structure constant and the electron, proton and Planck masses. Our approach
permits a systematic evaluation of measure proposals; with the causal patch
measure, we find no runaway of the primordial density contrast and the
cosmological constant to large values.Comment: 40 pages, 5 figures; discussion of measures extended, version to
appear in Phys. Rev.
Disintegrin targeting of an αvβ3 integrin-over-expressing high-metastatic human osteosarcoma with echistatin inhibits cell proliferation, migration, invasion and adhesion in vitro.
The in vitro efficacy of the disintegrin echistatin was tested on a high-metastatic variant of 143B human osteosarcoma, 143B-LM4, which over-expresses αvβ3 integrin. Echistatin is an RGD cyclic peptide and an antagonist of αvβ3 integrin. In the present study, echistatin inhibited cell proliferation, migration, invasion, and adhesion of 143B-LM4 cells. 143B-LM4 cell proliferation decreased after treatment with echistatin in a time-dependent and dose-dependent manner (P <0.01). In vitro migration and invasion of 143B-LM4 cells were also inhibited by echistatin in a dose-dependent manner (P <0.01, respectively). Cell adhesion to vitronectin of 143B-LM4 cells was also inhibited by echistatin in a dose-dependent manner (P <0.01). These results suggest that αvβ3 integrin may be an effective target for osteosarcoma
What can the observation of nonzero curvature tell us?
The eternally inflating multiverse provides a consistent framework to
understand coincidences and fine-tuning in the universe. As such, it provides
the possibility of finding another coincidence: if the amount of slow-roll
inflation was only slightly more than the anthropic threshold, then spatial
curvature might be measurable. We study this issue in detail, particularly
focusing on the question: "If future observations reveal nonzero curvature,
what can we conclude?" We find that whether an observable signal arises or not
depends crucially on three issues: the cosmic history just before the
observable inflation, the measure adopted to define probabilities, and the
nature of the correlation between the tunneling and slow-roll parts of the
potential. We find that if future measurements find positive curvature at
\Omega_k < -10^-4, then the framework of the eternally inflating multiverse is
excluded with high significance. If the measurements instead reveal negative
curvature at \Omega_k > 10^-4, then we can conclude (1) diffusive (new or
chaotic) eternal inflation did not occur in our immediate past; (2) our
universe was born by a bubble nucleation; (3) the probability measure does not
reward volume increase; and (4) the origin of the observed slow-roll inflation
is an accidental feature of the potential, not due to a theoretical mechanism.
Discovery of \Omega_k > 10^-4 would also give us nontrivial information about
the correlation between tunneling and slow-roll; e.g. a strong correlation
favoring large N would be excluded in certain measures. We also ask whether the
current constraint on \Omega_k is consistent with multiverse expectations,
finding that the answer is yes, except for certain cases. In the course of this
work we were led to consider vacuum decay branching ratios, and found that it
is more likely than one might guess that the decays are dominated by a single
channel.Comment: 46 pages, 5 figures; reference updates and typo corrections arising
from final Phys. Rev. D copy editin
Re/Os constraint on the time-variability of the fine-structure constant
We argue that the accuracy by which the isochron parameters of the decay
are determined by dating iron meteorites may
not directly constrain the possible time-dependence of the decay rate and hence
of the fine-structure constant . From this point of view, some of the
attempts to analyze the Oklo constraint and the results of the QSO absorption
lines are re-examined.Comment: 7 pages, 3 figures; v2, revised top sentence on p.
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