35,053 research outputs found
The Lorentzian distance formula in noncommutative geometry
For almost twenty years, a search for a Lorentzian version of the well-known
Connes' distance formula has been undertaken. Several authors have contributed
to this search, providing important milestones, and the time has now come to
put those elements together in order to get a valid and functional formula.
This paper presents a historical review of the construction and the proof of a
Lorentzian distance formula suitable for noncommutative geometry.Comment: 16 pages, final form, few references adde
Current medical treatment of estrogen receptor-positive breast cancer
Approximately 80% of breast cancers (BC) are estrogen receptor (ER)-positive and thus endocrine therapy (ET) should be considered complementary to surgery in the majority of patients. The advantages of oophorectomy, adrenalectomy and hypophysectomy in women with advanced BC have been demonstrated many years ago, and currently ET consist of (i) ovarian function suppression (OFS), usually obtained using gonadotropin-releasing hormone agonists (GnRHa), (ii) selective estrogen receptor modulators or down-regulators (SERMs or SERDs), (iii) aromatase inhibitors (AIs), or a combination of two or more drugs. For patients aged less than 50 years and ER+ BC, there is no conclusive evidence that the combination of OFS and SERMs (i.e. tamoxifen) or chemotherapy is superior to OFS alone. Tamoxifen users exhibit a reduced risk of BC, both invasive and in situ, especially during the first 5 years of therapy, and extending the treatment to 10 years further reduced the risk of recurrences. SERDs (i.e. fulvestrant) are especially useful in the neoadjuvant treatment of advanced BC, alone or in combination with either cytotoxic agents or AIs. There are two types of AIs: type I are permanent steroidal inhibitors of aromatase, while type II are reversible nonsteroidal inhibitors. Several studies demonstrated the superiority of the third-generation AIs (i.e. anastrozole and letrozole) compared with tamoxifen, and adjuvant therapy with AIs reduces the recurrence risk especially in patients with advanced BC. Unfortunately, some cancers are or became ET-resistant, and thus other drugs have been suggested in combination with SERMs or AIs, including cyclin-dependent kinase 4/6 inhibitors (palbociclib) and mammalian target of rapamycin (mTOR) inhibitors, such as everolimus. Further studies are required to confirm their real usefulness
Quantum metamaterial without local control
A quantum metamaterial can be implemented as a quantum coherent 1D array of
qubits placed in a transmission line. The properties of quantum metamaterials
are determined by the local quantum state of the system. Here we show that a
spatially-periodic quantum state of such a system can be realized without
direct control of the constituent qubits, by their interaction with the
initializing ("priming") pulses sent through the system in opposite directions.
The properties of the resulting quantum photonic crystal are determined by the
choice of the priming pulses. This proposal can be readily generalized to other
implementations of quantum metamaterials.Comment: 6 pages, 5 figure
On the heating of source of the Orion KL hot core
We present images of the J=10-9 rotational lines of HC3N in the vibrationally
excited levels 1v7, 1v6 and 1v5 of the hot core (HC) in Orion KL. The images
show that the spatial distribution and the size emission from the 1v7 and 1v5
levels are different. While the J=10-9 1v7 line has a size of 4''x 6'' and
peaks 1.1'' NE of the 3 mm continuum peak, the J=10--9 1v5 line emission is
unresolved (<3'') and peaks 1.3'' south of the 3 mm peak. This is a clear
indication that the HC is composed of condensations with very different
temperatures (170 K for the 1v7 peak and K for the 1v5 peak). The
temperature derived from the 1v7 and 1v5 lines increases with the projected
distance to the suspected main heating source I. Projection effects along the
line of sight could explain the temperature gradient as produced by source I.
However, the large luminosity required for source I, >5 10^5 Lsolar, to explain
the 1v5 line suggests that external heating by this source may not dominate the
heating of the HC. Simple model calculations of the vibrationally excited
emission indicate that the HC can be internally heated by a source with a
luminosity of 10^5 Lsolar, located 1.2'' SW of the 1v5 line peak (1.8'' south
of source I). We also report the first detection of high-velocity gas from
vibrationally excited HC3N emission. Based on excitation arguments we conclude
that the main heating source is also driving the molecular outflow. We
speculate that all the data presented in this letter and the IR images are
consistent with a young massive protostar embedded in an edge-on disk.Comment: 13 pages, 3 figures, To be published in Ap.J. Letter
b -> s Transitions: A New Frontier for Indirect SUSY Searches
The present unitarity triangle fit, whose essential input is represented by
the s to d and b to d transition processes, fully agrees with the SM. However,
most of the phenomena involving b to s transitions are still largely unexplored
and hence b to s phenomenology still constitutes a place for new physics
manifestations, in spite of the tremendous experimental and theoretical
progress on B to X_s gamma. We perform a systematic study of the CP conserving
and violating SUSY contributions to b to s processes in a generic MSSM. We
consider gluino exchange contributions including NLO QCD corrections and
lattice hadronic matrix elements for Delta B = 2 and Delta B = 1 processes. We
take into account all available experimental information on processes involving
b to s transitions (B to X_s gamma, B to X_s l^+ l^- and the lower bound on the
B_s - bar B_s mass difference Delta M_s). We study the correlations among the
relevant observables under scrutiny at present or in a not too far future:
Delta M_s and the amount of CP violation in B to phi K_s, B_s to J/psi phi, B
to X_s gamma. In particular we discuss the recent data by BaBar and BELLE on
the time-dependent CP asymmetry in the decay B to phi K_s which suggest a
deviation from the SM expectation. Our results show that the processes
involving b to s transitions represent a splendid opportunity to constrain
different MSSM realizations, and, even more important, that they offer concrete
prospects to exhibit SUSY signals at B factories and hadron colliders in spite
of all the past frustration in FCNC searches of new physics hints.Comment: 20 pages, 8 figures. Bug in the code corrected, figures for RL and
RL=RR cases and some conclusions change
Electrical resistivity of the Ti4O7 Magneli phase under high pressure
We have measured resistivity as a function of temperature and pressure of
Ti4O7 twinned crystals using different contact configurations. Pressures over
4kbar depress the localization of bipolarons and allow the study of the
electrical conduction of the bipolaronic phase down to low temperatures. For
pressures P > 40 kbar the bipolaron formation transition is suppressed and a
nearly pressure independent behavior is obtained for the resistivity. We
observed an anisotropic conduction. When current is injected parallel to the
principal axis, a metallic conduction with interacting carrier effects is
predominant. A superconducting state was not obtained down to 1.2 K, although
evidences of the proximity of a quantum critical point were noticed. While when
current is injected non-parallel to the crystal's principal axis, we obtained a
logarithmic divergence of the resistivity at low temperatures. For this case,
our results for the high pressure regime can be interpreted in the framework of
interacting carriers (polarons or bipolarons) scattered by Two Level Systems.Comment: 9 Revtex pages, 12 EPS figures included, submitted to The European
Physical Journal B. Contact author: C. Acha (e-mail address: [email protected]
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