Archivi categoria: Dibattiti

Sono impegnati in lunghe discussioni sulla fisica e filosofia attraverso e-mail e nei forum su Internet. Alcuni di loro sono un po 'brutto, ma la maggior parte sono stati condotti a buon gusto. Eccoli, sia per il piacere della lettura ed i miei scopi di archiviazione.

Dio — A Personal Story

I want to wrap up this series on atheism with a personal story about the point in time where I started diverging from the concept of God. I was very young then, about five years old. I had lost a pencil. It had just slipped out of my schoolbag, which was nothing more than a plastic basket with open weaves and a handle. When I realized that I had lost the pencil, I was quite upset. I think I was worried that I would get a scolding for my carelessness. Vedi, my family wasn’t rich. We were slightly better off than the households in our neighborhood, but quite poor by any global standards. The new pencil was, a me, a prized possession.

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The Origins of Gods

The atheist-theist debate boils down to a simple question — Did humans discover God? O, did we invent Him? The difference between discovering and inventing is the similar to the one between believing and knowing. Theist believe that there was a God to be discovered. Atheists “sapere” that we humans invented the concept of God. Belief and knowledge differ only slightly — knowledge is merely a very very strong belief. A belief is considered knowledge when it fits in nicely with a larger worldview, which is very much like how a hypothesis in physics becomes a theory. While a theory (such as Quantum Mechanics, per esempio) is considered to be knowledge (or the way the physical world really is), it is best not to forget the its lowly origin as a mere hypothesis. My focus in this post is the possible origin of the God hypothesis.

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Atheism and Unreal God

The only recourse an atheist can have against this argument based on personal experience is that the believer is either is misrepresenting his experience or is mistaken about it. I am not willing to pursue that line of argument. I know that I am undermining my own stance here, but I would like to give the theist camp some more ammunition for this particular argument, and make it more formal.

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Atheism vs. God Experience

I have a reason for delaying this post on the fifth and last argument for God by Dr. William Lane Craig. It holds more potency than immediately obvious. While it is easy to write it off because it is a subjective, experiential argument, the lack of credence we attribute to subjectivity is in itself a result of our similarly subjective acceptance of what we consider objective reason and rationality. I hope that this point will become clearer as you read this post and the next one.

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Atheism and the Morality of the Godless

In the previous post, we considered the cosmological argument (that the Big Bang theory is an affirmation of a God) and a teleological argument (that the highly improbable fine-tuning of the universe proves the existence of intelligent creation). We saw that the cosmological argument is nothing more than an admission of our ignorance, although it may be presented in any number of fancy forms (such as the cause of the universe is an uncaused cause, which is God, per esempio). The teleological argument comes from a potentially wilful distortion of the anthropic principle. The next one that Dr. Craig puts forward is the origin of morality, which has no grounding if you assume that atheism is true.

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Atheism – Christian God, or Lack Thereof

Prof. William Lane Craig is way more than a deist; he is certainly a theist. Infatti, he is more than that; he believes that God is as described in the scriptures of his flavor of Christianity. I am not an expert in that field, so I don’t know exactly what that flavor is. But the arguments he gave do not go much farther than the deism. He gave five arguments to prove that God exists, and he invited Hitchens to refute them. Hitchens did not; almeno, not in an enumerated and sequential fashion I plan to do here.

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Rischio – Wiley Fincad Webinar

Questo post è una versione modificata delle mie risposte in un Webinar Pannello-dibattito organizzato da Wiley-Finance e Fincad. Il Webcast liberamente disponibili è legata nel post, e contiene risposte da altri partecipanti — Paul Wilmott e Espen Huag. Una versione estesa di questo post potrebbe poi apparire come un articolo del Wilmott Magazine.

Qual è il rischio?

Quando usiamo la parola rischio in una normale conversazione, ha una connotazione negativa — il rischio di essere colpiti da una macchina, per esempio; ma non il rischio di vincere una lotteria. In finanza, rischio è sia positivo che negativo. Talvolta, si desidera l'esposizione a un certo tipo di rischio per controbilanciare qualche altra esposizione; talvolta, siete alla ricerca di rendimenti associati a un certo rischio. Rischio, in questo contesto, è quasi identico al concetto matematico di probabilità.

Ma anche nella finanza, si dispone di un tipo di rischio che è sempre negativo — è Operational Risk. Il mio interesse professionale in questo momento è nel ridurre al minimo il rischio operativo associato con le piattaforme di trading e di calcolo.

Come si misura il rischio?

Rischio di misurazione si riduce infine verso stimare la probabilità di una perdita in funzione di qualcosa — tipicamente l'intensità della perdita e tempo. Quindi è come chiedere — Qual è la probabilità di perdere un milione di dollari o di due milioni di dollari, domani o il giorno dopo?

La questione se siamo in grado di misurare il rischio è un altro modo di chiedere se possiamo capire la funzione di probabilità. In taluni casi, crediamo di poter — in Rischio di mercato, per esempio, abbiamo molto buoni modelli per questa funzione. Rischio di credito è tutta un'altra storia — anche se abbiamo pensato che avremmo potuto misurarla, abbiamo imparato nel modo più duro che probabilmente non poteva.

La domanda quanto sia efficace la misura è, è, secondo me, come chiedere a noi stessi, “Che cosa facciamo con un numero di probabilità?” Se faccio un calcolo di fantasia e dirvi che avete 27.3% probabilità di perdere un milione di domani, che cosa fare con quel pezzo di informazioni? Probabilità ha un significato ragionevole solo senso statistico, in eventi ad alta frequenza o grandi ensemble. Eventi di rischio, quasi per definizione, sono eventi a bassa frequenza e una serie di probabilità può avere solo un uso limitato pratico. Ma come strumento preventivo, probabilità accurata è grande, Soprattutto quando si strumenti di prezzo con profonda liquidità del mercato.

L'innovazione nella gestione del rischio.

L'innovazione in Risk disponibile in due versioni — uno è sul lato assunzione di rischi, che è in pricing, rischio di magazzinaggio e così via. Su questo fronte, lo facciamo bene, o almeno pensiamo che stiamo facendo bene, e l'innovazione in materia di prezzi e di modellazione è attiva. Il rovescio della medaglia è, naturalmente, la gestione del rischio. Qui, Credo che l'innovazione è in ritardo in realtà dietro eventi catastrofici. Una volta che abbiamo una crisi finanziaria, per esempio, facciamo un post-mortem, capire cosa è andato male e cercare di attuare dispositivi di sicurezza. Ma il successivo fallimento, naturalmente, sta per venire da un altro, tutto, Angolo di inaspettato.

Qual è il ruolo di Risk Management in una banca?

L'assunzione di rischi e la gestione del rischio sono due aspetti del business di una banca giorno per giorno. Questi due aspetti sembrano in conflitto tra loro, ma il conflitto è un caso. E 'attraverso la messa a punto di questo conflitto che una banca implementa la sua propensione al rischio. E 'come un equilibrio dinamico che può essere ottimizzato come desiderato.

Qual è il ruolo dei fornitori?

Nella mia esperienza, venditori sembrano influenzare i processi piuttosto che le metodologie di gestione del rischio, e in effetti di modellazione. Un sistema vended, tuttavia personalizzabile che può essere, viene fornito con le proprie ipotesi circa il flusso di lavoro, Gestione del ciclo di vita, ecc. I processi costruiti intorno al sistema dovranno adattarsi a queste ipotesi. Questa non è una brutta cosa. Almeno, sistemi vended popolari servono a standardizzare le pratiche di gestione del rischio.

The Big Bang Theory – Part II

After reading a paper by Ashtekar on quantum gravity and thinking about it, I realized what my trouble with the Big Bang theory was. It is more on the fundamental assumptions than the details. I thought I would summarize my thoughts here, more for my own benefit than anybody else’s.

Classical theories (including SR and QM) treat space as continuous nothingness; hence the term space-time continuum. In questa visione, objects exist in continuous space and interact with each other in continuous time.

Although this notion of space time continuum is intuitively appealing, it is, at best, incomplete. Consider, per esempio, a spinning body in empty space. It is expected to experience centrifugal force. Now imagine that the body is stationary and the whole space is rotating around it. Will it experience any centrifugal force?

It is hard to see why there would be any centrifugal force if space is empty nothingness.

GR introduced a paradigm shift by encoding gravity into space-time thereby making it dynamic in nature, rather than empty nothingness. Così, mass gets enmeshed in space (e il tempo), space becomes synonymous with the universe, and the spinning body question becomes easy to answer. Sì, it will experience centrifugal force if it is the universe that is rotating around it because it is equivalent to the body spinning. E, non, it won’t, if it is in just empty space. Ma “empty space” doesn’t exist. In the absence of mass, there is no space-time geometry.

Così, naturalmente, before the Big Bang (if there was one), there couldn’t be any space, nor indeed could there be any “before.” Note, tuttavia, that the Ashtekar paper doesn’t clearly state why there had to be a big bang. The closest it gets is that the necessity of BB arises from the encoding of gravity in space-time in GR. Despite this encoding of gravity and thereby rendering space-time dynamic, GR still treats space-time as a smooth continuum — a flaw, according to Ashtekar, that QG will rectify.

Ora, if we accept that the universe started out with a big bang (and from a small region), we have to account for quantum effects. Space-time has to be quantized and the only right way to do it would be through quantum gravity. Through QG, we expect to avoid the Big Bang singularity of GR, the same way QM solved the unbounded ground state energy problem in the hydrogen atom.

What I described above is what I understand to be the physical arguments behind modern cosmology. The rest is a mathematical edifice built on top of this physical (or indeed philosophical) fondazione. If you have no strong views on the philosophical foundation (or if your views are consistent with it), you can accept BB with no difficulty. Sfortunatamente, I do have differing views.

My views revolve around the following questions.

These posts may sound like useless philosophical musings, but I do have some concrete (and in my opinion, important) results, listed below.

There is much more work to be done on this front. But for the next couple of years, with my new book contract and pressures from my quant career, I will not have enough time to study GR and cosmology with the seriousness they deserve. I hope to get back to them once the current phase of spreading myself too thin passes.

What is Space?

This sounds like a strange question. We all know what space is, it is all around us. When we open our eyes, we see it. Se vedere per credere, then the question “Che cos'è lo spazio?” indeed is a strange one.

Ad essere onesti, we don’t actually see space. We see only objects which we assume are in space. Rather, we define space as whatever it is that holds or contains the objects. It is the arena where objects do their thing, the backdrop of our experience. In altre parole, experience presupposes space and time, and provides the basis for the worldview behind the currently popular interpretations of scientific theories.

Although not obvious, this definition (or assumption or understanding) of space comes with a philosophical baggage — that of realism. The realist’s view is predominant in the current understanding of Einstien’s theories as well. But Einstein himself may not have embraced realism blindly. Why else would he say:

In order to break away from the grip of realism, we have to approach the question tangentially. One way to do it is by studying the neuroscience and cognitive basis of sight, which after all provides the strongest evidence to the realness of space. Spazio, nell'insieme, is the experience associated with sight. Another way is to examine experiential correlates of other senses: What is sound?

When we hear something, what we hear is, naturalmente, suono. We experience a tone, an intensity and a time variation that tell us a lot about who is talking, what is breaking and so on. But even after stripping off all the extra richness added to the experience by our brain, the most basic experience is still a “sound.” We all know what it is, but we cannot explain it in terms more basic than that.

Now let’s look at the sensory signal responsible for hearing. As we know, these are pressure waves in the air that are created by a vibrating body making compressions and depressions in the air around it. Much like the ripples in a pond, these pressure waves propagate in almost all directions. They are picked up by our ears. By a clever mechanism, the ears perform a spectral analysis and send electric signals, which roughly correspond to the frequency spectrum of the waves, to our brain. Notare che, so far, we have a vibrating body, bunching and spreading of air molecules, and an electric signal that contains information about the pattern of the air molecules. We do not have sound yet.

The experience of sound is the magic our brain performs. It translates the electrical signal encoding the air pressure wave patterns to a representation of tonality and richness of sound. Sound is not the intrinsic property of a vibrating body or a falling tree, it is the way our brain chooses to represent the vibrations or, more precisely, the electrical signal encoding the spectrum of the pressure waves.

Doesn’t it make sense to call sound an internal cognitive representation of our auditory sensory inputs? If you agree, then reality itself is our internal representation of our sensory inputs. This notion is actually much more profound that it first appears. If sound is representation, so is smell. So is space.

Figure
Figura: Illustration of the process of brain’s representation of sensory inputs. Odors are a representation of the chemical compositions and concentration levels our nose senses. Suoni sono una mappatura delle onde di pressione aria prodotta da un oggetto vibrante. In vista, la nostra rappresentazione è lo spazio, e forse il tempo. Tuttavia, we do not know what it is the representation of.

We can examine it and fully understand sound because of one remarkable fact — we have a more powerful sense, namely our sight. Sight enables us to understand the sensory signals of hearing and compare them to our sensory experience. Infatti, sight enables us to make a model describing what sound is.

Why is it that we do not know the physical cause behind space? Dopotutto, we know of the causes behind the experiences of smell, suono, etc. The reason for our inability to see beyond the visual reality is in the hierarchy of senses, best illustrated using an example. Let’s consider a small explosion, like a firecracker going off. When we experience this explosion, we will see the flash, hear the report, smell the burning chemicals and feel the heat, if we are close enough.

The qualia of these experiences are attributed to the same physical event — the explosion, the physics of which is well understood. Ora, let’s see if we can fool the senses into having the same experiences, in the absence of a real explosion. The heat and the smell are fairly easy to reproduce. The experience of the sound can also be created using, per esempio, a high-end home theater system. How do we recreate the experience of the sight of the explosion? A home theater experience is a poor reproduction of the real thing.

In principle at least, we can think of futuristic scenarios such as the holideck in Star Trek, where the experience of the sight can be recreated. But at the point where sight is also recreated, is there a difference between the real experience of the explosion and the holideck simulation? The blurring of the sense of reality when the sight experience is simulated indicates that sight is our most powerful sense, and we have no access to causes beyond our visual reality.

Visual perception is the basis of our sense of reality. All other senses provide corroborating or complementing perceptions to the visual reality.

[This post has borrowed quite a bit from my book.]