Score
Title
86
AskScience Panel of Scientists XVIII
2972
What is the effect, positive or negative, of receiving multiple immunizations at the same time; such as when the military goes through "shot lines" to receive all deployment related vaccines?
54
AskScience AMA Series: I am Melinda Krahenbuhl and I am the director of the Reed Research Reactor, the only nuclear reactor operated primarily by undergraduate students. AMA!
1567
Ask Anything Wednesday - Biology, Chemistry, Neuroscience, Medicine, Psychology
1122
What triggers beta particles to form, and for what reason can they not penetrate substantially thick aluminium?
1241
If capacitance increases as distance between plates decreases, why aren't there very small 1F capacitors?
1048
is it possible to move an object in circular motion using magnets?
58
Do wild animals get physical addictions to substances?
6
How can brain cells cause tumours even though they can not multiply?
17
What causes the increased grip on paper when you lick your finger?
11
Would someone who got into an accident that put them into a coma for a couple of weeks still be addicted to a drug that they were addicted to prior to the accident? Why or why not?
1
Why do you loose the coefficient when you differentiate ln(2x) and then integrate it to ln(x)?
4
Why does sleep deprivation and lack of sleep increase depression?
7
Is there any evidence that pornography is a public health risk?
3
How fast does a sun blow up? Not as in life span, but say a supernova, how long would it take for the process to complete?
3
Can the effect of a "bunker buster" be accurately predicted, in relation to the target's compressive strength?
0
What are the basic units of measurement, IE time, distance, mass etc, that can be used to derive every other unit, such as joules, power, or magnetic force?
37150
Why is it that during winter it's not uncommon to have days with abnormally high temperature and summer-like weather, but in the summer it never drops to winter-like weather for a day?
33
How does Positron Emission Topography (PET) work?
1
Why are mercury salts a common first choice for heavy atom soaks in protein crystallography?
99
What happens to the spin of an electron when it leaves a nucleus?
1
Is there any evidence to suggest that biracial people are less susceptible to genetic diseases?
1
How does homolytic fission make radicals? Don't both of the atoms still have the same amount of electrons before the covalent bond and after the bond is split?
2
What kind of sound do the stars make?
10
What happens if a natural gas deposit in the ground ignites?
7
How can we hear when someone is smiling?
10
How does the Hubble Telescope take pictures?
1
Do genetics influence the way one's voice sounds?
2
[Physics] What makes us distinguish between hollow and solid objects so easily by just tapping the surface?
4
Is there anything that can bond to TRPV1 receptors that would completely or relatively dull capsaicin before ingesting it?
7
Do you burn the same number of calories during a given activity when you're fit as when you're unfit?
0
Can someone explain my questions about the orbits of the James Webb Space Telescope?
1
How are defining mutations in haplogroups chosen?
8
What about the properties of bronze makes it good for musical instruments and bells?
1
How many cell layers thick is the human epidermis?
5
Why does sand clump together when water is added?
3
How do the laws of conservation work with the concept of 'isolated system' being that quantum fields are boundless?
8
How are decisions made on where large hydroelectric dams are located?
73
If the moon was created from an impact with Earth, could there be “Earth rocks” deep within the Moon?
4
How are we able to put more space/memory into processors, GPU's, ram, hard drives, etc. as time progresses?
8
Have animals been observed using facial expressions to communicate among themselves?
1450 rumnscurvy The difference between String Field Theory and String theory is, in the broadest of sense, the same as the difference between Quantum Field Theory and Quantum Mechanics. QFT supercedes Quantum Mechanics in that it allows particle creation and annihilation dynamically. QM's basic building block is the Schrodinger equation, you're finding how a particle that you suppose already exists evolves when inside a potential that already exists, and never worry about how both of those things are generated. You can infer from that a whole lot more, but you will run into difficulties describing more complicated problems. In QFT, these things are not always fundamental, it allows us to derive a more microscopic view of e.g. the electromagnetic potential of a charged object, you can derive the famous 1/r^2 law. String Theory is much the same, its basic building block is the action for one string as it moves through space. Again, from knowing that you can infer a whole load of stuff (particle states, anomalies, dimensions of space, existence of branes, etc.) but centrally String theory does not have a proper way of treating strings being created and annihilated dynamically out of the vacuum. We assume they can, and we can figure out many properties of what happens when it does, but the formalism is somewhat lacking. String Field theory exists to re-employ the techniques that made QFT an improvement over QM in this circumstance to solve what seems like a similar obstacle.
32 samloveshummus In quantum field theory, you take spacetime as the domain in which all of the things you're studying (electron fields, electromagnetic fields etc) "live". In **string theory** this is turned on its head, because you take the *string worldsheet itself* to be the domain on which all the things you're studying live. In particular, the spacetime coordinates that tell you the string's position are themselves treated as quantum fields that live on the worldsheet. **String field theory** is the attempt to put this back the right way up: to treat spacetime as the domain and the strings as the things that live in that domain, instead of vice-versa. For practical calculations such as scattering amplitudes, they give the same answers where applicable - but the way they arrive at those answers is fundamentally from a completely different direction. String field theory is still in a much less mature state than string theory - basic things from string theory such as superstring loop amplitudes are not well understood at all.
206 JulianSchwinger I hesitate to give such a short answer, but here we go. > String field theory (SFT) is a formalism in string theory in which the dynamics of relativistic strings is reformulated in the language of quantum field theory. I appreciate this summary because it implies the heart of SFT. It is a "reformulation" of String Theory to match Quantum Field Theory (QFT). In this sense, SFT is essentially a boiled down version of String Theory in order to replicate QFT. One way of interpreting this ability of String Theory is that QFT is a subsidiary of String Theory (i.e. a person can derive QFT from String Theory if they interpret SFT correctly). Now to your question. String Theory is the over-arching theoretical framework that attempts to unify physics. String Field Theory is a "simplified" version that attempts to mimick our current best approximation, showing that String Theory would be a parent of QFT (in some sense). Quantum Field Theory is our current best approximation which we think is an approximation because of certain details that are left out (which is why we are researching String Theory). This is my translation of the Wikipedia article. A more detailed explanation would require someone with more expertise than I have. Edit: I would encourage everyone to also ready u/rumnscurvy's comment. It has a good analogy that sheds more light on the relation between String Theory and String Field Theory than my clumsy use of quotation marks around simplified. Sources: [Wikipedia Article on String Field Theory](https://en.wikipedia.org/wiki/String_field_theory)
31 rantonels At the risk of excessive simplification: String theory is not a QFT, for a number of reasons. One key reason is that it is quantum gravity, and quantum gravity cannot be a QFT. String field theory is an approximation to string theory which emphasizes the more QFT-like aspects of string theory in some regimes in which the theory is indeed QFT-like. Recall that each vibrational state of a string is a particle. What you do in SFT is not much far away from introducing a quantum field-like object for each such particle-like object to build a QFT-like system.
1448 0 rumnscurvy The difference between String Field Theory and String theory is, in the broadest of sense, the same as the difference between Quantum Field Theory and Quantum Mechanics. QFT supercedes Quantum Mechanics in that it allows particle creation and annihilation dynamically. QM's basic building block is the Schrodinger equation, you're finding how a particle that you suppose already exists evolves when inside a potential that already exists, and never worry about how both of those things are generated. You can infer from that a whole lot more, but you will run into difficulties describing more complicated problems. In QFT, these things are not always fundamental, it allows us to derive a more microscopic view of e.g. the electromagnetic potential of a charged object, you can derive the famous 1/r^2 law. String Theory is much the same, its basic building block is the action for one string as it moves through space. Again, from knowing that you can infer a whole load of stuff (particle states, anomalies, dimensions of space, existence of branes, etc.) but centrally String theory does not have a proper way of treating strings being created and annihilated dynamically out of the vacuum. We assume they can, and we can figure out many properties of what happens when it does, but the formalism is somewhat lacking. String Field theory exists to re-employ the techniques that made QFT an improvement over QM in this circumstance to solve what seems like a similar obstacle.
31 0 samloveshummus In quantum field theory, you take spacetime as the domain in which all of the things you're studying (electron fields, electromagnetic fields etc) "live". In **string theory** this is turned on its head, because you take the *string worldsheet itself* to be the domain on which all the things you're studying live. In particular, the spacetime coordinates that tell you the string's position are themselves treated as quantum fields that live on the worldsheet. **String field theory** is the attempt to put this back the right way up: to treat spacetime as the domain and the strings as the things that live in that domain, instead of vice-versa. For practical calculations such as scattering amplitudes, they give the same answers where applicable - but the way they arrive at those answers is fundamentally from a completely different direction. String field theory is still in a much less mature state than string theory - basic things from string theory such as superstring loop amplitudes are not well understood at all.
205 0 JulianSchwinger I hesitate to give such a short answer, but here we go. > String field theory (SFT) is a formalism in string theory in which the dynamics of relativistic strings is reformulated in the language of quantum field theory. I appreciate this summary because it implies the heart of SFT. It is a "reformulation" of String Theory to match Quantum Field Theory (QFT). In this sense, SFT is essentially a boiled down version of String Theory in order to replicate QFT. One way of interpreting this ability of String Theory is that QFT is a subsidiary of String Theory (i.e. a person can derive QFT from String Theory if they interpret SFT correctly). Now to your question. String Theory is the over-arching theoretical framework that attempts to unify physics. String Field Theory is a "simplified" version that attempts to mimick our current best approximation, showing that String Theory would be a parent of QFT (in some sense). Quantum Field Theory is our current best approximation which we think is an approximation because of certain details that are left out (which is why we are researching String Theory). This is my translation of the Wikipedia article. A more detailed explanation would require someone with more expertise than I have. Edit: I would encourage everyone to also ready u/rumnscurvy's comment. It has a good analogy that sheds more light on the relation between String Theory and String Field Theory than my clumsy use of quotation marks around simplified. Sources: [Wikipedia Article on String Field Theory](https://en.wikipedia.org/wiki/String_field_theory)
33 0 rantonels At the risk of excessive simplification: String theory is not a QFT, for a number of reasons. One key reason is that it is quantum gravity, and quantum gravity cannot be a QFT. String field theory is an approximation to string theory which emphasizes the more QFT-like aspects of string theory in some regimes in which the theory is indeed QFT-like. Recall that each vibrational state of a string is a particle. What you do in SFT is not much far away from introducing a quantum field-like object for each such particle-like object to build a QFT-like system.