Asymptotically exponential hitting times and metastability: a pathwise approach without reversibility

We study the hitting times of Markov processes to target set $G$, starting from a reference configuration $x_0$ or its basin of attraction. The configuration $x_0$ can correspond to the bottom of a (meta)stable well, while the target $G$ could be either a set of saddle (exit) points of the well, or a set of further (meta)stable configurations. Three types of results are reported: (1) A general theory is developed, based on the path-wise approach to metastability, which has three important attributes. First, it is general in that it does not assume reversibility of the process, does not focus only on hitting times to rare events and does not assume a particular starting measure. Second, it relies only on the natural hypothesis that the mean hitting time to $G$ is asymptotically longer than the mean recurrence time to $x_0$ or $G$. Third, despite its mathematical simplicity, the approach yields precise and explicit bounds on the corrections to exponentiality. (2) We compare and relate different metastability conditions proposed in the literature so to eliminate potential sources of confusion. This is specially relevant for evolutions of infinite-volume systems, whose treatment depends on whether and how relevant parameters (temperature, fields) are adjusted. (3) We introduce the notion of early asymptotic exponential behavior to control time scales asymptotically smaller than the mean-time scale. This control is particularly relevant for systems with unbounded state space where nucleations leading to exit from metastability can happen anywhere in the volume. We provide natural sufficient conditions on recurrence times for this early exponentiality to hold and show that it leads to estimations of probability density functions

Z', new fermions and flavor changing processes, constraints on E6_6 models from μ\mu --> eee

We study a new class of flavor changing interactions, which can arise in models based on extended gauge groups (rank $>$4) when new charged fermions are present together with a new neutral gauge boson. We discuss the cases in which the flavor changing couplings in the new neutral current coupled to the $Z^\prime$ are theoretically expected to be large, implying that the observed suppression of neutral flavor changing transitions must be provided by heavy $Z^\prime$ masses together with small $Z$-$Z^\prime$ mixing angles. Concentrating on E$_6$ models, we show how the tight experimental limit on $\mu \rightarrow eee$ implies serious constraints on the $Z^\prime$ mass and mixing angle. We conclude that if the value of the flavor changing parameters is assumed to lie in a theoretically natural range, in most cases the presence of a $Z^\prime$ much lighter than 1 TeV is unlikely.Comment: plain tex, 22 pages + 2 pages figures in PostScript (appended after `\bye'), UM-TH 92-1

Why is it Important to Assess and Treat Alexithymia in the Cardiologic Field? An Overview of the Literature

Background: Alexithymia has been found to be associated with several somatic illnesses, such as cardiovascular, indicating that it might be a risk factor for early death in the long-term course of post-myocardial infarction. From the cardiology perspective, the aim was to collect current evidence about the relationship between alexithymia and somatic illness. Methods: The literature was synthesized and summarized in a narrative format. The literature search was carried out in PubMed. Pertinent studies published in the last 50 years written in English were included and organized by three main topics (“The relation between alexithymia and somatic illness from the cardiology perspective”; “How do assess alexithymia?”; “Treating alexithymia”) to be discussed. Results: High alexithymia is a dimensional trait that affects around 10% of the general population and up to 55% of people with essential hypertension. Also, the link between alexithymia and cardiovascular activity has been pointed out. There are several validated tools to assess alexithymia, as well as treatment options. Conclusion: Knowledge about the main features of alexithymia, as well as its assessment and treatment, can promote a multifactorial approach to the primary, secondary, and tertiary prevention of cardiac diseases

Model independent analysis of the simultaneous mixing of gauge bosons and mixing of fermions

We discuss the case of simultaneous mixing of gauge bosons and mixing of fermions in a model independent way and for a variety of extra-fermion representations. In this context we analyze a class of lepton family violating processes, namely Z --> e tau, Z --> mu tau, Z --> e mu, mu --> e e e, tau --> e e e, tau --> mu mu mu, tau --> e mu mu and tau --> mu e e in the presence of one extra neutral gauge boson, Z', with universal, non-universal or family changing couplings. We derive bounds on the combined effect of Z-Z' mixing and ordinary--exotic lepton mixing.Comment: 13 pages, LaTeX, Submitted to Phys. Rev.

Unconventional superstring derived E6_{\bf 6} models and neutrino phenomenology

Conventional superstring derived E$_6$ models can accommodate small neutrino masses if a discrete symmetry is imposed which forbids tree level Dirac neutrino masses but allows for radiative mass generation. Since the only possible symmetries of this kind are known to be generation dependent, we explore the possibility that the three sets of light states in each generation do not have the same assignments with respect to the 27 of $E_6$, leading to non universal gauge interactions under the additional $U(1)'$ factors for the known fermions. We argue that models realising such a scenario are viable, with their structure being constrained mainly by the requirement of the absence of flavor changing neutral currents in the Higgs sector. Moreover, in contrast to the standard case, rank 6 models are not disfavoured with respect to rank 5. By requiring the number of light neutral states to be minimal, these models have an almost unique pattern of neutrino masses and mixings. We construct a model based on the unconventional assignment scenario in which (with a natural choice of the parameters) m_{\nut}\sim O(10)eV is generated at one loop, m_{\num} is generated at two loops and lies in a range interesting for the solar neutrino problem, and \nue remains massless. In addition, since baryon and lepton number are conserved, there is no proton decay in the model. To illustrate the non-standard phenomenology implied by our scheme we also discuss a second scenario in which an attempt for solving the solar neutrino puzzle with matter enhanced oscillations and practically massless neutrinos can be formulated, and in which peculiar effects for the \num --> \nut conversion of the upward-going atmospheric neutrinos could arise as well.Comment: Plain Tex, 33 pages, 3 PostScript figures (uses epsf.tex). Modified file-format. No changes in the tex

Surviving to acute myocardial infarction: The role of psychological factors and alexithymia in delayed time to searching care: A systematic review

The time from symptom onset to reperfusion is a critical determinant of myocardial salvage and clinical outcomes in patients with acute myocardial infarction (AMI). This time period could be delayed if people do not seek help promptly and/or if the health system is not efficient in responding quickly and attending to these individuals. The aim of this study was to identify psychological factors associated with pre-hospital delay (PHD) or patients’ decisional delay (PDD) in people with an ongoing AMI. A search in PubMed/Medline from 1990 to 2021 with the keywords “pre-hospital delay” OR “prehospital delay” OR “patient delay” OR “decisional delay” OR “care seeking behavior” AND “psychological factors” OR “alexithymia” AND “myocardial infarction” was performed. Thirty-six studies were included, involving 10.389 patients. Wrong appraisal, interpretation and causal beliefs about symptoms, denial of the severity of the symptoms and high levels of alexithymia were found related to longer PHD or PDD. Alexithymia may be an overarching construct that explains the disparate findings of the studies exploring the role of psychological factors in PHD or PDD. Further studies are needed in order to analyse the role of alexithymia in patients with risk factors for AMI to prevent delay

Observable Electron EDM and Leptogenesis

In the context of the minimal supersymmetric seesaw model, the CP-violating neutrino Yukawa couplings might induce an electron EDM. The same interactions may also be responsible for the generation of the observed baryon asymmetry of the Universe via leptogenesis. We identify in a model-independent way those patterns within the seesaw models which predict an electron EDM at a level probed by planned laboratory experiments and show that negative searches on \tau-> e \gamma decay may provide the strongest upper bound on the electron EDM. We also conclude that a possible future detection of the electron EDM is incompatible with thermal leptogenesis, even when flavour effects are accounted for.Comment: 26 pages, 6 figure

Surviving to acute myocardial infarction: The role of psychological factors and alexithymia in delayed time to searching care: A systematic review

The time from symptom onset to reperfusion is a critical determinant of myocardial salvage and clinical outcomes in patients with acute myocardial infarction (AMI). This time period could be delayed if people do not seek help promptly and/or if the health system is not efficient in responding quickly and attending to these individuals. The aim of this study was to identify psychological factors associated with pre-hospital delay (PHD) or patients’ decisional delay (PDD) in people with an ongoing AMI. A search in PubMed/Medline from 1990 to 2021 with the keywords “pre-hospital delay” OR “prehospital delay” OR “patient delay” OR “decisional delay” OR “care seeking behavior” AND “psychological factors” OR “alexithymia” AND “myocardial infarction” was performed. Thirty-six studies were included, involving 10.389 patients. Wrong appraisal, interpretation and causal beliefs about symptoms, denial of the severity of the symptoms and high levels of alexithymia were found related to longer PHD or PDD. Alexithymia may be an overarching construct that explains the disparate findings of the studies exploring the role of psychological factors in PHD or PDD. Further studies are needed in order to analyse the role of alexithymia in patients with risk factors for AMI to prevent delay

Searching for Strongly Interacting Massive Particles (SIMPs)

We consider laboratory experiments that can detect stable, neutral strongly interacting massive particles (SIMPs). We explore the SIMP annihilation cross section from its minimum value (restricted by cosmological bounds) to the barn range, and vary the mass values from a GeV to a TeV. We calculate, as a function of the SIMP-nucleon cross section, the minimum nucleon number A for which there should be binding in a nucleus. We consider accelerator mass spectrometry with a gold (A=200) target, and compute the likely abundance of anomalous gold nuclei if stable neutral SIMPs exist. We also consider the prospects and problems of detecting such particles at the Tevatron. We estimate optimistically that such detection might be possible for SIMPs with SIMP-nucleon cross sections larger than 0.1 millibarn and masses between 25 and 50 GeV.Comment: RevTeX, 10 pages, 3 figures; Minor updates to match published versio

Relaxation Height in Energy Landscapes: an Application to Multiple Metastable States

The study of systems with multiple (not necessarily degenerate) metastable states presents subtle difficulties from the mathematical point of view related to the variational problem that has to be solved in these cases. We introduce the notion of relaxation height in a general energy landscape and we prove sufficient conditions which are valid even in presence of multiple metastable states. We show how these results can be used to approach the problem of multiple metastable states via the use of the modern theories of metastability. We finally apply these general results to the Blume--Capel model for a particular choice of the parameters ensuring the existence of two multiple, and not degenerate in energy, metastable states